Revert "Revert "Balder/group multiple commits rebased 1""

19 files changed, 905 insertions, 416 deletions

diff --git a/searchlib/src/tests/transactionlog/translogclient_test.cpp b/searchlib/src/tests/transactionlog/translogclient_test.cpp
index 861023b79b7..5b28fdc6567 100644
--- a/searchlib/src/tests/transactionlog/translogclient_test.cpp
+++ b/searchlib/src/tests/transactionlog/translogclient_test.cpp
@@ -5,7 +5,6 @@
 #include <vespa/vespalib/objects/identifiable.h>
 #include <vespa/searchlib/index/dummyfileheadercontext.h>
 #include <vespa/fastos/file.h>
-#include <map>
 
 #include <vespa/log/log.h>
 LOG_SETUP("translogclient_test");
@@ -45,7 +44,7 @@ private:
     bool partialUpdateTest();
     bool testVisitOverGeneratedDomain();
     bool testRemove();
-    void createAndFillDomain(const vespalib::string & name, DomainPart::Crc crcMethod, size_t preExistingDomains);
+    void createAndFillDomain(const vespalib::string & name, Encoding encoding, size_t preExistingDomains);
     void verifyDomain(const vespalib::string & name);
     void testCrcVersions();
     bool testVisitOverPreExistingDomain();
@@ -221,11 +220,12 @@ public:
 
 IMPLEMENT_IDENTIFIABLE(TestIdentifiable, Identifiable);
 
+constexpr size_t DEFAULT_PACKET_SIZE = 0xf000;
 bool Test::partialUpdateTest()
 {
     bool retval(false);
     DummyFileHeaderContext fileHeaderContext;
-    TransLogServer tlss("test7", 18377, ".", fileHeaderContext, 0x10000);
+    TransLogServer tlss("test7", 18377, ".", fileHeaderContext, DomainConfig().setPartSizeLimit(0x10000));
     TransLogClient tls("tcp/localhost:18377");
 
     TransLogClient::Session::UP s1 = openDomainTest(tls, "test1");
@@ -239,9 +239,8 @@ bool Test::partialUpdateTest()
     vespalib::ConstBufferRef bb(os.c_str(), os.size());
     LOG(info, "DU : %s", myhex(bb.c_str(), bb.size()).c_str());
     Packet::Entry e(7, du.getClass().id(), bb);
-    Packet pa;
+    Packet pa(DEFAULT_PACKET_SIZE);
     pa.add(e);
-    pa.close();
     ASSERT_TRUE(session.commit(vespalib::ConstBufferRef(pa.getHandle().c_str(), pa.getHandle().size())));
 
     CallBackUpdate ca;
@@ -312,29 +311,24 @@ bool Test::fillDomainTest(TransLogClient::Session * s1, const vespalib::string &
     Packet::Entry e2(2, 2, vespalib::ConstBufferRef("Content in buffer B", 20));
     Packet::Entry e3(3, 1, vespalib::ConstBufferRef("Content in buffer C", 20));
 
-    Packet a;
-    ASSERT_TRUE (a.add(e1));
-    Packet b;
-    ASSERT_TRUE (b.add(e2));
-    ASSERT_TRUE (b.add(e3));
-    ASSERT_TRUE (!b.add(e1));
-    a.close();
-    b.close();
+    Packet a(DEFAULT_PACKET_SIZE);
+    a.add(e1);
+    Packet b(DEFAULT_PACKET_SIZE);
+    b.add(e2);
+    b.add(e3);
+    EXPECT_EXCEPTION(b.add(e1), std::runtime_error, "");
     ASSERT_TRUE (s1->commit(vespalib::ConstBufferRef(a.getHandle().c_str(), a.getHandle().size())));
     ASSERT_TRUE (s1->commit(vespalib::ConstBufferRef(b.getHandle().c_str(), b.getHandle().size())));
-    try {
-        s1->commit(vespalib::ConstBufferRef(a.getHandle().c_str(), a.getHandle().size()));
-        ASSERT_TRUE(false);
-    } catch (const std::exception & e) {
-        EXPECT_EQUAL(vespalib::string("commit failed with code -2. server says: Exception during commit on " + name + " : Incomming serial number(1) must be bigger than the last one (3)."), e.what());
-    }
+    EXPECT_EXCEPTION(s1->commit(vespalib::ConstBufferRef(a.getHandle().c_str(), a.getHandle().size())),
+                     std::runtime_error,
+                     "commit failed with code -2. server says: Exception during commit on " + name + " : Incomming serial number(1) must be bigger than the last one (3).");
     EXPECT_EQUAL(a.size(), 1u);
     EXPECT_EQUAL(a.range().from(), 1u);
     EXPECT_EQUAL(a.range().to(), 1u);
     EXPECT_EQUAL(b.size(), 2u);
     EXPECT_EQUAL(b.range().from(), 2u);
     EXPECT_EQUAL(b.range().to(), 3u);
-    EXPECT_TRUE(a.merge(b));
+    a.merge(b);
     EXPECT_EQUAL(a.size(), 3u);
     EXPECT_EQUAL(a.range().from(), 1u);
     EXPECT_EQUAL(a.range().to(), 3u);
@@ -353,41 +347,35 @@ void Test::fillDomainTest(TransLogClient::Session * s1, size_t numPackets, size_
 {
     size_t value(0);
     for(size_t i=0; i < numPackets; i++) {
-        std::unique_ptr<Packet> p(new Packet());
+        std::unique_ptr<Packet> p(new Packet(DEFAULT_PACKET_SIZE));
         for(size_t j=0; j < numEntries; j++, value++) {
             Packet::Entry e(value+1, j+1, vespalib::ConstBufferRef((const char *)&value, sizeof(value)));
-            if ( ! p->add(e) ) {
-                p->close();
+            p->add(e);
+            if ( p->sizeBytes() > DEFAULT_PACKET_SIZE ) {
                 ASSERT_TRUE(s1->commit(vespalib::ConstBufferRef(p->getHandle().c_str(), p->getHandle().size())));
-                p.reset(new Packet());
-                ASSERT_TRUE(p->add(e));
+                p.reset(new Packet(DEFAULT_PACKET_SIZE));
             }
         }
-        p->close();
         ASSERT_TRUE(s1->commit(vespalib::ConstBufferRef(p->getHandle().c_str(), p->getHandle().size())));
     }
 }
 
 
 void
-Test::fillDomainTest(TransLogClient::Session * s1,
-                     size_t numPackets, size_t numEntries,
-                     size_t entrySize)
+Test::fillDomainTest(TransLogClient::Session * s1, size_t numPackets, size_t numEntries, size_t entrySize)
 {
     size_t value(0);
     std::vector<char> entryBuffer(entrySize); 
     for(size_t i=0; i < numPackets; i++) {
-        std::unique_ptr<Packet> p(new Packet());
+        std::unique_ptr<Packet> p(new Packet(DEFAULT_PACKET_SIZE));
         for(size_t j=0; j < numEntries; j++, value++) {
             Packet::Entry e(value+1, j+1, vespalib::ConstBufferRef((const char *)&entryBuffer[0], entryBuffer.size()));
-            if ( ! p->add(e) ) {
-                p->close();
+            p->add(e);
+            if ( p->sizeBytes() > DEFAULT_PACKET_SIZE ) {
                 ASSERT_TRUE(s1->commit(vespalib::ConstBufferRef(p->getHandle().c_str(), p->getHandle().size())));
-                p.reset(new Packet());
-                ASSERT_TRUE(p->add(e));
+                p.reset(new Packet(DEFAULT_PACKET_SIZE));
             }
         }
-        p->close();
         ASSERT_TRUE(s1->commit(vespalib::ConstBufferRef(p->getHandle().c_str(), p->getHandle().size())));
     }
 }
@@ -410,8 +398,7 @@ Test::countFiles(const vespalib::string &dir)
 
 
 void
-Test::checkFilledDomainTest(const TransLogClient::Session::UP &s1,
-                            size_t numEntries)
+Test::checkFilledDomainTest(const TransLogClient::Session::UP &s1, size_t numEntries)
 {
     SerialNum b(0), e(0);
     size_t c(0);
@@ -489,7 +476,7 @@ getMaxSessionRunTime(TransLogServer &tls, const vespalib::string &domain)
 bool Test::testVisitOverGeneratedDomain()
 {
     DummyFileHeaderContext fileHeaderContext;
-    TransLogServer tlss("test7", 18377, ".", fileHeaderContext, 0x10000);
+    TransLogServer tlss("test7", 18377, ".", fileHeaderContext, DomainConfig().setPartSizeLimit(0x10000));
     TransLogClient tls("tcp/localhost:18377");
 
     vespalib::string name("test1");
@@ -504,10 +491,11 @@ bool Test::testVisitOverGeneratedDomain()
     return true;
 }
 
-void Test::createAndFillDomain(const vespalib::string & name, DomainPart::Crc crcMethod, size_t preExistingDomains)
+void Test::createAndFillDomain(const vespalib::string & name, Encoding encoding, size_t preExistingDomains)
 {
     DummyFileHeaderContext fileHeaderContext;
-    TransLogServer tlss("test13", 18377, ".", fileHeaderContext, 0x10000, 4, crcMethod);
+    TransLogServer tlss("test13", 18377, ".", fileHeaderContext,
+                        DomainConfig().setPartSizeLimit(0x1000000).setEncoding(encoding), 4);
     TransLogClient tls("tcp/localhost:18377");
 
     createDomainTest(tls, name, preExistingDomains);
@@ -518,7 +506,7 @@ void Test::createAndFillDomain(const vespalib::string & name, DomainPart::Crc cr
 void Test::verifyDomain(const vespalib::string & name)
 {
     DummyFileHeaderContext fileHeaderContext;
-    TransLogServer tlss("test13", 18377, ".", fileHeaderContext, 0x10000);
+    TransLogServer tlss("test13", 18377, ".", fileHeaderContext, DomainConfig().setPartSizeLimit(0x1000000));
     TransLogClient tls("tcp/localhost:18377");
     TransLogClient::Session::UP s1 = openDomainTest(tls, name);
     visitDomainTest(tls, s1.get(), name);
@@ -526,8 +514,8 @@ void Test::verifyDomain(const vespalib::string & name)
 
 void Test::testCrcVersions()
 {
-    createAndFillDomain("ccitt_crc32", DomainPart::ccitt_crc32, 0);
-    createAndFillDomain("xxh64", DomainPart::xxh64, 1);
+    createAndFillDomain("ccitt_crc32", Encoding::Crc::ccitt_crc32, 0);
+    createAndFillDomain("xxh64", Encoding::Crc::xxh64, 1);
 
     verifyDomain("ccitt_crc32");
     verifyDomain("xxh64");
@@ -536,7 +524,7 @@ void Test::testCrcVersions()
 bool Test::testRemove()
 {
     DummyFileHeaderContext fileHeaderContext;
-    TransLogServer tlss("testremove", 18377, ".", fileHeaderContext, 0x10000);
+    TransLogServer tlss("testremove", 18377, ".", fileHeaderContext, DomainConfig().setPartSizeLimit(0x10000));
     TransLogClient tls("tcp/localhost:18377");
 
     vespalib::string name("test-delete");
@@ -553,7 +541,7 @@ bool Test::testVisitOverPreExistingDomain()
 {
     // Depends on Test::testVisitOverGeneratedDomain()
     DummyFileHeaderContext fileHeaderContext;
-    TransLogServer tlss("test7", 18377, ".", fileHeaderContext, 0x10000);
+    TransLogServer tlss("test7", 18377, ".", fileHeaderContext, DomainConfig().setPartSizeLimit(0x10000));
     TransLogClient tls("tcp/localhost:18377");
 
     vespalib::string name("test1");
@@ -607,7 +595,7 @@ void Test::testMany()
     const unsigned int TOTAL_NUM_ENTRIES = NUM_PACKETS * NUM_ENTRIES;
     {
         DummyFileHeaderContext fileHeaderContext;
-        TransLogServer tlss("test8", 18377, ".", fileHeaderContext, 0x80000);
+        TransLogServer tlss("test8", 18377, ".", fileHeaderContext, DomainConfig().setPartSizeLimit(0x80000));
         TransLogClient tls("tcp/localhost:18377");
 
         createDomainTest(tls, "many", 0);
@@ -630,7 +618,7 @@ void Test::testMany()
     }
     {
         DummyFileHeaderContext fileHeaderContext;
-        TransLogServer tlss("test8", 18377, ".", fileHeaderContext, 0x1000000);
+        TransLogServer tlss("test8", 18377, ".", fileHeaderContext, DomainConfig().setPartSizeLimit(0x1000000));
         TransLogClient tls("tcp/localhost:18377");
 
         TransLogClient::Session::UP s1 = openDomainTest(tls, "many");
@@ -658,7 +646,7 @@ void Test::testErase()
     const unsigned int TOTAL_NUM_ENTRIES = NUM_PACKETS * NUM_ENTRIES;
     {
         DummyFileHeaderContext fileHeaderContext;
-        TransLogServer tlss("test12", 18377, ".", fileHeaderContext, 0x80000);
+        TransLogServer tlss("test12", 18377, ".", fileHeaderContext, DomainConfig().setPartSizeLimit(0x80000));
         TransLogClient tls("tcp/localhost:18377");
 
         createDomainTest(tls, "erase", 0);
@@ -667,7 +655,7 @@ void Test::testErase()
     }
     {
         DummyFileHeaderContext fileHeaderContext;
-        TransLogServer tlss("test12", 18377, ".", fileHeaderContext, 0x1000000);
+        TransLogServer tlss("test12", 18377, ".", fileHeaderContext, DomainConfig().setPartSizeLimit(0x1000000));
         TransLogClient tls("tcp/localhost:18377");
 
         TransLogClient::Session::UP s1 = openDomainTest(tls, "erase");
@@ -757,7 +745,7 @@ Test::testSync()
     const unsigned int TOTAL_NUM_ENTRIES = NUM_PACKETS * NUM_ENTRIES;
 
     DummyFileHeaderContext fileHeaderContext;
-    TransLogServer tlss("test9", 18377, ".", fileHeaderContext, 0x1000000);
+    TransLogServer tlss("test9", 18377, ".", fileHeaderContext, DomainConfig().setPartSizeLimit(0x1000000));
     TransLogClient tls("tcp/localhost:18377");
 
     createDomainTest(tls, "sync", 0);
@@ -782,7 +770,7 @@ Test::testTruncateOnVersionMismatch()
     size_t countOld(0);
     DummyFileHeaderContext fileHeaderContext;
     {
-        TransLogServer tlss("test11", 18377, ".", fileHeaderContext, 0x1000000);
+        TransLogServer tlss("test11", 18377, ".", fileHeaderContext, DomainConfig().setPartSizeLimit(0x1000000));
         TransLogClient tls("tcp/localhost:18377");
 
         createDomainTest(tls, "sync", 0);
@@ -803,7 +791,7 @@ Test::testTruncateOnVersionMismatch()
     EXPECT_EQUAL(static_cast<ssize_t>(sizeof(tmp)), f.Write2(tmp, sizeof(tmp)));
     EXPECT_TRUE(f.Close());
     {
-        TransLogServer tlss("test11", 18377, ".", fileHeaderContext, 0x1000000);
+        TransLogServer tlss("test11", 18377, ".", fileHeaderContext, DomainConfig().setPartSizeLimit(0x10000));
         TransLogClient tls("tcp/localhost:18377");
         TransLogClient::Session::UP s1 = openDomainTest(tls, "sync");
         uint64_t from(0), to(0);
@@ -829,7 +817,7 @@ Test::testTruncateOnShortRead()
 
     DummyFileHeaderContext fileHeaderContext;
     {
-        TransLogServer tlss(topdir, 18377, ".", fileHeaderContext, 0x10000);
+        TransLogServer tlss(topdir, 18377, ".", fileHeaderContext, DomainConfig().setPartSizeLimit(0x10000));
         TransLogClient tls(tlsspec);
         
         createDomainTest(tls, domain, 0);
@@ -845,7 +833,7 @@ Test::testTruncateOnShortRead()
         EXPECT_EQUAL(2u, countFiles(dir));
     }
     {
-        TransLogServer tlss(topdir, 18377, ".", fileHeaderContext, 0x10000);
+        TransLogServer tlss(topdir, 18377, ".", fileHeaderContext, DomainConfig().setPartSizeLimit(0x10000));
         TransLogClient tls(tlsspec);
         TransLogClient::Session::UP s1 = openDomainTest(tls, domain);
         checkFilledDomainTest(s1, TOTAL_NUM_ENTRIES);
@@ -861,7 +849,7 @@ Test::testTruncateOnShortRead()
         trfile.Close();
     }
     {
-        TransLogServer tlss(topdir, 18377, ".", fileHeaderContext, 0x10000);
+        TransLogServer tlss(topdir, 18377, ".", fileHeaderContext, DomainConfig().setPartSizeLimit(0x10000));
         TransLogClient tls(tlsspec);
         TransLogClient::Session::UP s1 = openDomainTest(tls, domain);
         checkFilledDomainTest(s1, TOTAL_NUM_ENTRIES - 1);
diff --git a/searchlib/src/tests/transactionlogstress/translogstress.cpp b/searchlib/src/tests/transactionlogstress/translogstress.cpp
index abba84b75b6..6f2581d3799 100644
--- a/searchlib/src/tests/transactionlogstress/translogstress.cpp
+++ b/searchlib/src/tests/transactionlogstress/translogstress.cpp
@@ -8,7 +8,6 @@
 #include <vespa/searchlib/index/dummyfileheadercontext.h>
 #include <vespa/fastos/app.h>
 #include <iostream>
-#include <stdexcept>
 #include <sstream>
 
 #include <vespa/log/log.h>
@@ -221,7 +220,6 @@ FeederThread::~FeederThread() {}
 void
 FeederThread::commitPacket()
 {
-    _packet.close();
     const vespalib::nbostream& stream = _packet.getHandle();
     if (!_session->commit(ConstBufferRef(stream.c_str(), stream.size()))) {
         throw std::runtime_error(vespalib::make_string
@@ -236,8 +234,9 @@ FeederThread::commitPacket()
 bool
 FeederThread::addEntry(const Packet::Entry & e)
 {
-    //LOG(info, "FeederThread: add %s", EntryPrinter::toStr(e).c_str());
-    return _packet.add(e);
+    if (_packet.sizeBytes() > 0xf000) return false;
+    _packet.add(e);
+    return true;
 }
 
 void
@@ -699,7 +698,7 @@ TransLogStress::Main()
 
     // start transaction log server
     DummyFileHeaderContext fileHeaderContext;
-    TransLogServer tls("server", 17897, ".", fileHeaderContext, _cfg.domainPartSize);
+    TransLogServer tls("server", 17897, ".", fileHeaderContext, DomainConfig().setPartSizeLimit(_cfg.domainPartSize));
     TransLogClient client(tlsSpec);
     client.create(domain);
 
diff --git a/searchlib/src/vespa/searchlib/config/translogserver.def b/searchlib/src/vespa/searchlib/config/translogserver.def
index 74efe3fe68e..b1bdb3765b1 100644
--- a/searchlib/src/vespa/searchlib/config/translogserver.def
+++ b/searchlib/src/vespa/searchlib/config/translogserver.def
@@ -5,7 +5,7 @@ namespace=searchlib
 listenport int default=13700 restart
 
 ## Max file size (50M)
-filesizemax int default=50000000 restart
+filesizemax int default=50000000
 
 ## Server name to identify server.
 servername string default="tls" restart
@@ -22,3 +22,17 @@ maxthreads int default=4 restart
 
 ##Default crc method used
 crcmethod enum {ccitt_crc32, xxh64} default=xxh64
+
+## Control compression type.
+compression.type enum {NONE, LZ4, ZSTD} default=LZ4
+
+## Control compression level
+## LZ4 has normal range 1..9 while ZSTD has range 1..19
+## 9 is a reasonable default for both
+compression.level int default=9
+
+## How large a chunk can grow in memory before beeing flushed
+chunk.sizelimit int default = 256000  # 256k
+
+## How long a chunk can reside in memory befor ebeeing flushed to disk.
+chunk.agelimit double default = 0.0010 # 10 milliseconds
diff --git a/searchlib/src/vespa/searchlib/transactionlog/CMakeLists.txt b/searchlib/src/vespa/searchlib/transactionlog/CMakeLists.txt
index d964c88fe29..0755d07b403 100644
--- a/searchlib/src/vespa/searchlib/transactionlog/CMakeLists.txt
+++ b/searchlib/src/vespa/searchlib/transactionlog/CMakeLists.txt
@@ -1,9 +1,11 @@
 # Copyright 2017 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
 vespa_add_library(searchlib_transactionlog OBJECT
     SOURCES
+    chunks.cpp
     common.cpp
     domain.cpp
     domainpart.cpp
+    ichunk.cpp
     nosyncproxy.cpp
     session.cpp
     trans_log_server_explorer.cpp
diff --git a/searchlib/src/vespa/searchlib/transactionlog/chunks.cpp b/searchlib/src/vespa/searchlib/transactionlog/chunks.cpp
new file mode 100644
index 00000000000..dea0ccf9b9a
--- /dev/null
+++ b/searchlib/src/vespa/searchlib/transactionlog/chunks.cpp
@@ -0,0 +1,128 @@
+// Copyright 2017 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+
+#include "chunks.h"
+#include <vespa/vespalib/util/stringfmt.h>
+#include <vespa/vespalib/util/compressor.h>
+#include <vespa/vespalib/data/databuffer.h>
+
+using std::runtime_error;
+using std::make_unique;
+using vespalib::make_string;
+using vespalib::compression::compress;
+using vespalib::compression::decompress;
+using vespalib::compression::CompressionConfig;
+using vespalib::DataBuffer;
+using vespalib::ConstBufferRef;
+using vespalib::nbostream;
+
+namespace search::transactionlog {
+
+namespace {
+void verifyCrc(nbostream & is, Encoding::Crc crcType) {
+    if (is.size() < sizeof(int32_t) * 2) {
+        throw runtime_error(make_string("Not even room for the crc and length. Only %zu bytes left", is.size()));
+    }
+    size_t start = is.rp();
+    is.adjustReadPos(is.size() - sizeof(int32_t));
+    int32_t crc(0);
+    is >> crc;
+    is.rp(start);
+    int32_t crcVerify = Encoding::calcCrc(crcType, is.c_str(), is.size() - sizeof(crc));
+    if (crc != crcVerify) {
+        throw runtime_error(make_string("Got bad crc : crcVerify = %d, expected %d",
+                                        static_cast<int>(crcVerify), static_cast<int>(crc)));
+    }
+    is.rp(start);
+}
+
+Encoding::Compression
+toCompression(CompressionConfig::Type type) {
+    switch (type) {
+        case CompressionConfig::ZSTD:
+            return Encoding::Compression::zstd;
+        case CompressionConfig::LZ4:
+            return Encoding::Compression::lz4;
+        case CompressionConfig::NONE:
+            return Encoding::Compression::none;
+        default:
+            abort();
+    }
+}
+
+}
+
+Encoding
+CCITTCRC32None::onEncode(nbostream &os) const {
+    size_t start = os.wp();
+    assert(getEntries().size() == 1);
+    serializeEntries(os);
+    os << int32_t(Encoding::calcCrc(Encoding::Crc::ccitt_crc32, os.c_str()+start, os.size() - start));
+    return Encoding(Encoding::Crc::ccitt_crc32, Encoding::Compression::none);
+}
+
+void CCITTCRC32None::onDecode(nbostream &is) {
+    verifyCrc(is, Encoding::Crc::ccitt_crc32);
+    nbostream data(is.peek(), is.size() - sizeof(int32_t));
+    deserializeEntries(data);
+    is.adjustReadPos(is.size());
+}
+
+Encoding
+XXH64None::onEncode(nbostream &os) const {
+    size_t start = os.wp();
+    assert(getEntries().size() == 1);
+    serializeEntries(os);
+    os << int32_t(Encoding::calcCrc(Encoding::Crc::xxh64, os.c_str()+start, os.size() - start));
+    return Encoding(Encoding::Crc::xxh64, Encoding::Compression::none);
+}
+
+void XXH64None::onDecode(nbostream &is) {
+    verifyCrc(is, Encoding::Crc::xxh64);
+    nbostream data(is.peek(), is.size() - sizeof(int32_t));
+    deserializeEntries(data);
+    is.adjustReadPos(is.size());
+}
+
+void
+XXH64Compressed::decompress(nbostream & is) {
+    uint32_t uncompressedLen;
+    is >> uncompressedLen;
+    vespalib::DataBuffer uncompressed;
+    ConstBufferRef compressed(is.peek(), is.size()-sizeof(uint32_t)*2);
+    ::decompress(_type, uncompressedLen, compressed, uncompressed, false);
+    nbostream data(uncompressed.getData(), uncompressed.getDataLen());
+    deserializeEntries(data);
+    is.adjustReadPos(is.size());
+}
+
+XXH64Compressed::XXH64Compressed(CompressionConfig::Type type, uint8_t level)
+    : _type(type),
+      _level(level)
+{ }
+
+Encoding
+XXH64Compressed::compress(nbostream & os, Encoding::Crc crc) const {
+    nbostream org;
+    serializeEntries(org);
+    DataBuffer compressed;
+    CompressionConfig cfg(_type, _level, 80);
+    ConstBufferRef uncompressed(org.c_str(), org.size());
+    Encoding::Compression actual = toCompression(::compress(cfg, uncompressed, compressed, false));
+    size_t start = os.wp();
+    os.write(compressed.getData(), compressed.getDataLen());
+    os << int32_t(Encoding::calcCrc(crc, os.c_str()+start, os.size() - start));
+    return Encoding(Encoding::Crc::xxh64, actual);
+}
+
+Encoding
+XXH64Compressed::onEncode(IChunk::nbostream &os) const {
+    return compress(os, Encoding::Crc::xxh64);
+}
+
+void
+XXH64Compressed::onDecode(IChunk::nbostream &is) {
+    verifyCrc(is, Encoding::Crc::xxh64);
+    decompress(is);
+}
+
+}
diff --git a/searchlib/src/vespa/searchlib/transactionlog/chunks.h b/searchlib/src/vespa/searchlib/transactionlog/chunks.h
new file mode 100644
index 00000000000..cf88bc0a3ed
--- /dev/null
+++ b/searchlib/src/vespa/searchlib/transactionlog/chunks.h
@@ -0,0 +1,38 @@
+// Copyright 2017 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+
+#pragma once
+
+#include "ichunk.h"
+#include <vespa/vespalib/util/compressionconfig.h>
+
+namespace search::transactionlog {
+
+class XXH64None : public IChunk {
+protected:
+    Encoding onEncode(nbostream &os) const override;
+    void onDecode(nbostream &is) override;
+public:
+};
+
+class CCITTCRC32None : public IChunk {
+protected:
+    Encoding onEncode(nbostream &os) const override;
+    void onDecode(nbostream &is) override;
+public:
+};
+
+class XXH64Compressed : public IChunk {
+public:
+    using CompressionConfig = vespalib::compression::CompressionConfig;
+    XXH64Compressed(CompressionConfig::Type, uint8_t level);
+protected:
+    void decompress(nbostream & os);
+    Encoding compress(nbostream & os, Encoding::Crc crc) const;
+    Encoding onEncode(nbostream &os) const override;
+    void onDecode(nbostream &is) override;
+private:
+    CompressionConfig::Type _type;
+    uint8_t                 _level;
+};
+
+}
diff --git a/searchlib/src/vespa/searchlib/transactionlog/common.cpp b/searchlib/src/vespa/searchlib/transactionlog/common.cpp
index a84e27b2e53..9bf43c8e244 100644
--- a/searchlib/src/vespa/searchlib/transactionlog/common.cpp
+++ b/searchlib/src/vespa/searchlib/transactionlog/common.cpp
@@ -1,14 +1,29 @@
 // Copyright 2017 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
 
 #include "common.h"
+#include <vespa/vespalib/util/stringfmt.h>
 #include <vespa/fastos/file.h>
 
 namespace search::transactionlog {
 
 using vespalib::nbostream;
 using vespalib::nbostream_longlivedbuf;
+using vespalib::make_string;
+using std::runtime_error;
 
-int makeDirectory(const char * dir)
+namespace {
+
+void throwRangeError(SerialNum prev, SerialNum next) __attribute__((noinline));
+
+void throwRangeError(SerialNum prev, SerialNum next) {
+    if (prev < next) return;
+    throw runtime_error(make_string("The new serialnum %zu is not higher than the old one %zu", next, prev));
+}
+
+}
+
+int
+makeDirectory(const char * dir)
 {
     int retval(-1);
 
@@ -22,7 +37,8 @@ int makeDirectory(const char * dir)
     return retval;
 }
 
-int64_t SerialNumRange::cmp(const SerialNumRange & b) const
+int64_t
+SerialNumRange::cmp(const SerialNumRange & b) const
 {
     int64_t diff(0);
     if ( ! (contains(b) || b.contains(*this)) ) {
@@ -34,7 +50,6 @@ int64_t SerialNumRange::cmp(const SerialNumRange & b) const
 Packet::Packet(const void * buf, size_t sz) :
      _count(0),
      _range(),
-     _limit(sz),
      _buf(static_cast<const char *>(buf), sz)
 {
     nbostream_longlivedbuf os(_buf.c_str(), sz);
@@ -49,18 +64,22 @@ Packet::Packet(const void * buf, size_t sz) :
     }
 }
 
-bool Packet::merge(const Packet & packet)
+void
+Packet::merge(const Packet & packet)
 {
-    bool retval(_range.to() < packet._range.from());
-    if (retval) {
-        _count += packet._count;
-        _range.to(packet._range.to());
-        _buf.write(packet.getHandle().c_str(), packet.getHandle().size());
+    if (_range.to() >= packet.range().from()) {
+        throwRangeError(_range.to(), packet.range().from());
     }
-    return retval;
+    if (_buf.empty()) {
+        _range.from(packet.range().from());
+    }
+    _count += packet._count;
+    _range.to(packet._range.to());
+    _buf.write(packet.getHandle().c_str(), packet.getHandle().size());
 }
 
-nbostream & Packet::Entry::deserialize(nbostream & os)
+nbostream &
+Packet::Entry::deserialize(nbostream & os)
 {
     _valid = false;
     int32_t len(0);
@@ -71,7 +90,8 @@ nbostream & Packet::Entry::deserialize(nbostream & os)
     return os;
 }
 
-nbostream & Packet::Entry::serialize(nbostream & os) const
+nbostream &
+Packet::Entry::serialize(nbostream & os) const
 {
     os << _unique << _type << static_cast<uint32_t>(_data.size());
     os.write(_data.c_str(), _data.size());
@@ -83,22 +103,21 @@ Packet::Entry::Entry(SerialNum u, Type t, const vespalib::ConstBufferRef & d) :
     _type(t),
     _valid(true),
     _data(d)
-{
-}
-
+{ }
 
-bool Packet::add(const Packet::Entry & e)
+void
+Packet::add(const Packet::Entry & e)
 {
-    bool retval((_buf.size() < _limit) && (_range.to() < e.serial()));
-    if (retval) {
-        if (_buf.empty()) {
-            _range.from(e.serial());
-        }
-        e.serialize(_buf);
-        _count++;
-        _range.to(e.serial());
+    if (_range.to() >= e.serial()) {
+        throwRangeError(_range.to(), e.serial());
     }
-    return retval;
+
+    if (_buf.empty()) {
+        _range.from(e.serial());
+    }
+    e.serialize(_buf);
+    _count++;
+    _range.to(e.serial());
 }
 
 }
diff --git a/searchlib/src/vespa/searchlib/transactionlog/common.h b/searchlib/src/vespa/searchlib/transactionlog/common.h
index db8b9727daa..0deceb2668a 100644
--- a/searchlib/src/vespa/searchlib/transactionlog/common.h
+++ b/searchlib/src/vespa/searchlib/transactionlog/common.h
@@ -69,21 +69,19 @@ public:
         vespalib::ConstBufferRef _data;
     };
 public:
-    Packet(size_t m=0xf000) : _count(0), _range(), _limit(m), _buf(m) { }
+    Packet(size_t reserved) : _count(0), _range(), _buf(reserved) { }
     Packet(const void * buf, size_t sz);
-    bool add(const Entry & data);
-    void close() { }
+    void add(const Entry & data);
     void clear() { _buf.clear(); _count = 0; _range.from(0); _range.to(0); }
     const SerialNumRange & range() const { return _range; }
     const vespalib::nbostream & getHandle() const { return _buf; }
     size_t                  size() const { return _count; }
     bool                   empty() const { return _count == 0; }
     size_t             sizeBytes() const { return _buf.size(); }
-    bool merge(const Packet & packet);
+    void merge(const Packet & packet);
 private:
     size_t                            _count;
     SerialNumRange                    _range;
-    size_t                            _limit;
     vespalib::nbostream_longlivedbuf  _buf;
 };
 
diff --git a/searchlib/src/vespa/searchlib/transactionlog/domain.cpp b/searchlib/src/vespa/searchlib/transactionlog/domain.cpp
index 88c2dd9ecc3..c03543e5599 100644
--- a/searchlib/src/vespa/searchlib/transactionlog/domain.cpp
+++ b/searchlib/src/vespa/searchlib/transactionlog/domain.cpp
@@ -20,28 +20,41 @@ using vespalib::MonitorGuard;
 using search::common::FileHeaderContext;
 using std::runtime_error;
 using namespace std::chrono_literals;
+using namespace std::chrono;
+using std::make_shared;
 
 namespace search::transactionlog {
 
-Domain::Domain(const string &domainName, const string & baseDir, Executor & commitExecutor,
-               Executor & sessionExecutor, uint64_t domainPartSize, DomainPart::Crc defaultCrcType,
-               const FileHeaderContext &fileHeaderContext) :
-    _defaultCrcType(defaultCrcType),
-    _commitExecutor(commitExecutor),
-    _sessionExecutor(sessionExecutor),
-    _sessionId(1),
-    _syncMonitor(),
-    _pendingSync(false),
-    _name(domainName),
-    _domainPartSize(domainPartSize),
-    _parts(),
-    _lock(),
-    _sessionLock(),
-    _sessions(),
-    _maxSessionRunTime(),
-    _baseDir(baseDir),
-    _fileHeaderContext(fileHeaderContext),
-    _markedDeleted(false)
+DomainConfig::DomainConfig()
+    : _encoding(Encoding::Crc::xxh64, Encoding::Compression::none),
+      _compressionLevel(9),
+      _partSizeLimit(0x10000000), // 256M
+      _chunkSizeLimit(0x40000),   // 256k
+      _chunkAgeLimit(1ms)
+{ }
+Domain::Domain(const string &domainName, const string & baseDir, FastOS_ThreadPool & threadPool,
+               Executor & commitExecutor, Executor & sessionExecutor, const DomainConfig & cfg,
+               const FileHeaderContext &fileHeaderContext)
+    : _config(cfg),
+      _currentChunk(std::make_unique<Chunk>()),
+      _lastSerial(0),
+      _threadPool(threadPool),
+      _commitExecutor(commitExecutor),
+      _sessionExecutor(sessionExecutor),
+      _sessionId(1),
+      _syncMonitor(),
+      _pendingSync(false),
+      _name(domainName),
+      _parts(),
+      _lock(),
+      _currentChunkMonitor(),
+      _sessionLock(),
+      _sessions(),
+      _maxSessionRunTime(),
+      _baseDir(baseDir),
+      _fileHeaderContext(fileHeaderContext),
+      _markedDeleted(false),
+      _self(nullptr)
 {
     int retval(0);
     if ((retval = makeDirectory(_baseDir.c_str())) != 0) {
@@ -59,12 +72,32 @@ Domain::Domain(const string &domainName, const string & baseDir, Executor & comm
     }
     _sessionExecutor.sync();
     if (_parts.empty() || _parts.crbegin()->second->isClosed()) {
-        _parts[lastPart].reset(new DomainPart(_name, dir(), lastPart, _defaultCrcType, _fileHeaderContext, false));
+        _parts[lastPart] = make_shared<DomainPart>(_name, dir(), lastPart, _config.getEncoding(),
+                                                   _config.getCompressionlevel(), _fileHeaderContext, false);
     }
+    _lastSerial = end();
+    _self = _threadPool.NewThread(this);
+    assert(_self);
 }
 
+Domain &
+Domain::setConfig(const DomainConfig & cfg) {
+    _config = cfg;
+    return *this;
+}
+
+void
+Domain::Run(FastOS_ThreadInterface *thisThread, void *) {
+
+    while (!thisThread->GetBreakFlag()) {
+        vespalib::MonitorGuard guard(_currentChunkMonitor);
+        guard.wait(duration_cast<milliseconds>(_config.getChunkAgeLimit()).count());
+        commitIfStale(guard);
+    }
+}
 void Domain::addPart(int64_t partId, bool isLastPart) {
-    DomainPart::SP dp(new DomainPart(_name, dir(), partId, _defaultCrcType, _fileHeaderContext, isLastPart));
+    auto dp = make_shared<DomainPart>(_name, dir(), partId, _config.getEncoding(),
+                                      _config.getCompressionlevel(), _fileHeaderContext, isLastPart);
     if (dp->size() == 0) {
         // Only last domain part is allowed to be truncated down to
         // empty size.
@@ -102,7 +135,16 @@ private:
     bool              & _pendingSync;
 };
 
-Domain::~Domain() { }
+Domain::~Domain() {
+    if (_self) {
+        _self->SetBreakFlag();
+        {
+            MonitorGuard guard(_currentChunkMonitor);
+            guard.broadcast();
+        }
+        _self->Join();
+    }
+}
 
 DomainInfo
 Domain::getDomainInfo() const
@@ -129,7 +171,7 @@ Domain::begin(const LockGuard & guard) const
     assert(guard.locks(_lock));
     SerialNum s(0);
     if ( ! _parts.empty() ) {
-        s = _parts.begin()->second->range().from();
+        s = _parts.cbegin()->second->range().from();
     }
     return s;
 }
@@ -147,7 +189,7 @@ Domain::end(const LockGuard & guard) const
     assert(guard.locks(_lock));
     SerialNum s(0);
     if ( ! _parts.empty() ) {
-        s = _parts.rbegin()->second->range().to();
+        s = _parts.crbegin()->second->range().to();
     }
     return s;
 }
@@ -267,7 +309,8 @@ void Domain::cleanSessions()
 
 namespace {
 
-void waitPendingSync(vespalib::Monitor &syncMonitor, bool &pendingSync)
+void
+waitPendingSync(vespalib::Monitor &syncMonitor, bool &pendingSync)
 {
     MonitorGuard guard(syncMonitor);
     while (pendingSync) {
@@ -277,18 +320,82 @@ void waitPendingSync(vespalib::Monitor &syncMonitor, bool &pendingSync)
 
 }
 
-void Domain::commit(const Packet & packet)
+
+Domain::Chunk::Chunk()
+    : _data(size_t(-1)),
+      _callBacks(),
+      _firstArrivalTime()
+{}
+
+Domain::Chunk::~Chunk() = default;
+void
+Domain::Chunk::add(const Packet &packet, Writer::DoneCallback onDone) {
+    if (_callBacks.empty()) {
+        _firstArrivalTime = steady_clock::now();
+    }
+    _data.merge(packet);
+    _callBacks.emplace_back(std::move(onDone));
+}
+
+microseconds
+Domain::Chunk::age() const {
+    if (_callBacks.empty()) {
+        return 0ms;
+    }
+    return duration_cast<microseconds>(steady_clock::now() - _firstArrivalTime);
+}
+
+void
+Domain::commit(const Packet & packet, Writer::DoneCallback onDone) {
+    std::unique_ptr<Chunk> completed;
+    vespalib::MonitorGuard guard(_currentChunkMonitor);
+    if (! (_lastSerial < packet.range().from())) {
+        throw runtime_error(make_string("Incomming serial number(%ld) must be bigger than the last one (%ld).",
+                                        packet.range().from(), _lastSerial));
+    } else {
+        _lastSerial = packet.range().to();
+    }
+    _currentChunk->add(packet, std::move(onDone));
+    if (_currentChunk->sizeBytes() > _config.getChunkSizeLimit()) {
+        completed = grabCurrentChunk(guard);
+    }
+    if (completed) {
+        commitChunk(std::move(_currentChunk), guard);
+    }
+}
+
+std::unique_ptr<Domain::Chunk>
+Domain::grabCurrentChunk(const vespalib::MonitorGuard & guard) {
+    assert(guard.monitors(_currentChunkMonitor));
+    auto chunk = std::move(_currentChunk);
+    _currentChunk = std::make_unique<Chunk>();
+    return chunk;
+}
+
+void
+Domain::commitIfStale(const vespalib::MonitorGuard & guard) {
+    assert(guard.monitors(_currentChunkMonitor));
+    if (_currentChunk->age() > _config.getChunkAgeLimit()) {
+        commitChunk(grabCurrentChunk(guard), guard);
+    }
+}
+
+void
+Domain::commitChunk(std::unique_ptr<Chunk> chunk, const vespalib::MonitorGuard & chunkOrderGuard)
 {
+    assert(chunkOrderGuard.monitors(_currentChunkMonitor));
+    const Packet & packet = chunk->getPacket();
     DomainPart::SP dp(_parts.rbegin()->second);
     vespalib::nbostream_longlivedbuf is(packet.getHandle().c_str(), packet.getHandle().size());
     Packet::Entry entry;
     entry.deserialize(is);
-    if (dp->byteSize() > _domainPartSize) {
+    if (dp->byteSize() > _config.getPartSizeLimit()) {
         waitPendingSync(_syncMonitor, _pendingSync);
         triggerSyncNow();
         waitPendingSync(_syncMonitor, _pendingSync);
         dp->close();
-        dp.reset(new DomainPart(_name, dir(), entry.serial(), _defaultCrcType, _fileHeaderContext, false));
+        dp = make_shared<DomainPart>(_name, dir(), entry.serial(), _config.getEncoding(),
+                                     _config.getCompressionlevel(), _fileHeaderContext, false);
         {
             LockGuard guard(_lock);
             _parts[entry.serial()] = dp;
diff --git a/searchlib/src/vespa/searchlib/transactionlog/domain.h b/searchlib/src/vespa/searchlib/transactionlog/domain.h
index c1ff9157a6f..553117959c7 100644
--- a/searchlib/src/vespa/searchlib/transactionlog/domain.h
+++ b/searchlib/src/vespa/searchlib/transactionlog/domain.h
@@ -8,16 +8,39 @@
 
 namespace search::transactionlog {
 
+class DomainConfig {
+public:
+    using microseconds = std::chrono::microseconds;
+    DomainConfig();
+    DomainConfig & setEncoding(Encoding v)          { _encoding = v; return *this; }
+    DomainConfig & setPartSizeLimit(size_t v)       { _partSizeLimit = v; return *this; }
+    DomainConfig & setChunkSizeLimit(size_t v)      { _chunkSizeLimit = v; return *this; }
+    DomainConfig & setChunkAgeLimit(microseconds v) { _chunkAgeLimit = v; return *this; }
+    DomainConfig & setCompressionLevel(uint8_t v)   { _compressionLevel = v; return *this; }
+    Encoding          getEncoding() const { return _encoding; }
+    size_t       getPartSizeLimit() const { return _partSizeLimit; }
+    size_t      getChunkSizeLimit() const { return _chunkSizeLimit; }
+    microseconds getChunkAgeLimit() const { return _chunkAgeLimit; }
+    uint8_t getCompressionlevel() const { return _compressionLevel; }
+private:
+    Encoding     _encoding;
+    uint8_t      _compressionLevel;
+    size_t       _partSizeLimit;
+    size_t       _chunkSizeLimit;
+    microseconds _chunkAgeLimit;
+};
+
 struct PartInfo {
     SerialNumRange range;
     size_t numEntries;
     size_t byteSize;
     vespalib::string file;
-    PartInfo(SerialNumRange range_in, size_t numEntries_in,
-             size_t byteSize_in,
-             vespalib::stringref file_in)
-        : range(range_in), numEntries(numEntries_in), byteSize(byteSize_in),
-          file(file_in) {}
+    PartInfo(SerialNumRange range_in, size_t numEntries_in, size_t byteSize_in, vespalib::stringref file_in)
+        : range(range_in),
+          numEntries(numEntries_in),
+          byteSize(byteSize_in),
+          file(file_in)
+    {}
 };
 
 struct DomainInfo {
@@ -35,22 +58,22 @@ struct DomainInfo {
 
 typedef std::map<vespalib::string, DomainInfo> DomainStats;
 
-class Domain
+class Domain final : public FastOS_Runnable
 {
 public:
     using SP = std::shared_ptr<Domain>;
     using Executor = vespalib::ThreadExecutor;
-    Domain(const vespalib::string &name, const vespalib::string &baseDir, Executor & commitExecutor,
-           Executor & sessionExecutor, uint64_t domainPartSize, DomainPart::Crc defaultCrcType,
+    Domain(const vespalib::string &name, const vespalib::string &baseDir, FastOS_ThreadPool & threadPool,
+           Executor & commitExecutor, Executor & sessionExecutor, const DomainConfig & cfg,
            const common::FileHeaderContext &fileHeaderContext);
 
-    virtual ~Domain();
+    ~Domain() override;
 
     DomainInfo getDomainInfo() const;
     const vespalib::string & name() const { return _name; }
     bool erase(SerialNum to);
 
-    void commit(const Packet & packet);
+    void commit(const Packet & packet, Writer::DoneCallback onDone);
     int visit(const Domain::SP & self, SerialNum from, SerialNum to, FRT_Supervisor & supervisor, FNET_Connection *conn);
 
     SerialNum begin() const;
@@ -77,8 +100,26 @@ public:
         return _sessionExecutor.execute(std::move(task));
     }
     uint64_t size() const;
-
+    Domain & setConfig(const DomainConfig & cfg);
 private:
+    void Run(FastOS_ThreadInterface *thisThread, void *arguments) override;
+    void commitIfStale(const vespalib::MonitorGuard & guard);
+    class Chunk {
+    public:
+        Chunk();
+        ~Chunk();
+        void add(const Packet & packet, Writer::DoneCallback onDone);
+        size_t sizeBytes() const { return _data.sizeBytes(); }
+        const Packet & getPacket() const { return _data; }
+        std::chrono::microseconds age() const;
+    private:
+        Packet _data;
+        std::vector<Writer::DoneCallback>     _callBacks;
+        std::chrono::steady_clock::time_point _firstArrivalTime;
+    };
+
+    std::unique_ptr<Chunk> grabCurrentChunk(const vespalib::MonitorGuard & guard);
+    void commitChunk(std::unique_ptr<Chunk> chunk, const vespalib::MonitorGuard & chunkOrderGuard);
     SerialNum begin(const vespalib::LockGuard & guard) const;
     SerialNum end(const vespalib::LockGuard & guard) const;
     size_t byteSize(const vespalib::LockGuard & guard) const;
@@ -95,22 +136,26 @@ private:
     using DomainPartList = std::map<int64_t, DomainPart::SP>;
     using DurationSeconds = std::chrono::duration<double>;
 
-    DomainPart::Crc     _defaultCrcType;
-    Executor          & _commitExecutor;
-    Executor          & _sessionExecutor;
-    std::atomic<int>    _sessionId;
-    vespalib::Monitor   _syncMonitor;
-    bool                _pendingSync;
-    vespalib::string    _name;
-    uint64_t            _domainPartSize;
-    DomainPartList      _parts;
-    vespalib::Lock      _lock;
-    vespalib::Lock      _sessionLock;
-    SessionList         _sessions;
-    DurationSeconds     _maxSessionRunTime;
-    vespalib::string    _baseDir;
+    DomainConfig           _config;
+    std::unique_ptr<Chunk> _currentChunk;
+    SerialNum              _lastSerial;
+    FastOS_ThreadPool    & _threadPool;
+    Executor             & _commitExecutor;
+    Executor             & _sessionExecutor;
+    std::atomic<int>       _sessionId;
+    vespalib::Monitor      _syncMonitor;
+    bool                   _pendingSync;
+    vespalib::string       _name;
+    DomainPartList         _parts;
+    vespalib::Lock         _lock;
+    vespalib::Monitor      _currentChunkMonitor;
+    vespalib::Lock         _sessionLock;
+    SessionList            _sessions;
+    DurationSeconds        _maxSessionRunTime;
+    vespalib::string       _baseDir;
     const common::FileHeaderContext &_fileHeaderContext;
-    bool                _markedDeleted;
+    bool                   _markedDeleted;
+    FastOS_ThreadInterface  * _self;
 };
 
 }
diff --git a/searchlib/src/vespa/searchlib/transactionlog/domainpart.cpp b/searchlib/src/vespa/searchlib/transactionlog/domainpart.cpp
index 35bdc71c963..f140fb93b96 100644
--- a/searchlib/src/vespa/searchlib/transactionlog/domainpart.cpp
+++ b/searchlib/src/vespa/searchlib/transactionlog/domainpart.cpp
@@ -2,7 +2,6 @@
 
 #include "domainpart.h"
 #include <vespa/vespalib/util/crc.h>
-#include <vespa/vespalib/xxhash/xxhash.h>
 #include <vespa/vespalib/util/stringfmt.h>
 #include <vespa/vespalib/data/fileheader.h>
 #include <vespa/searchlib/common/fileheadercontext.h>
@@ -27,37 +26,26 @@ namespace search::transactionlog {
 
 namespace {
 
-void
-handleSync(FastOS_FileInterface &file) __attribute__ ((noinline));
+constexpr size_t TARGET_PACKET_SIZE = 0x3f000;
 
 string
-handleWriteError(const char *text,
-                 FastOS_FileInterface &file,
-                 int64_t lastKnownGoodPos,
-                 const Packet::Entry &entry,
-                 int bufLen) __attribute__ ((noinline));
+handleWriteError(const char *text, FastOS_FileInterface &file, int64_t lastKnownGoodPos,
+                 SerialNumRange range, int bufLen) __attribute__ ((noinline));
 
 bool
-handleReadError(const char *text,
-                FastOS_FileInterface &file,
-                ssize_t len,
-                ssize_t rlen,
-                int64_t lastKnownGoodPos,
-                bool allowTruncate) __attribute__ ((noinline));
+handleReadError(const char *text, FastOS_FileInterface &file, ssize_t len, ssize_t rlen,
+                int64_t lastKnownGoodPos, bool allowTruncate) __attribute__ ((noinline));
 
-bool
-addPacket(Packet &packet,
-          const Packet::Entry &e) __attribute__ ((noinline));
+void handleSync(FastOS_FileInterface &file) __attribute__ ((noinline));
+void addPacket(Packet &packet, const Packet::Entry &e) __attribute__ ((noinline));
+bool tailOfFileIsZero(FastOS_FileInterface &file, int64_t lastKnownGoodPos) __attribute__ ((noinline));
 
-bool
-tailOfFileIsZero(FastOS_FileInterface &file, int64_t lastKnownGoodPos) __attribute__ ((noinline));
-
-bool
+void
 addPacket(Packet &packet, const Packet::Entry &e)
 {
     LOG(spam, "Adding serial #%" PRIu64 ", of type %d and size %zd into packet of size %zu and %zu bytes",
               e.serial(), e.type(), e.data().size(), packet.size(), packet.sizeBytes());
-    return ! packet.add(e);
+    packet.add(e);
 }
 
 void
@@ -72,21 +60,18 @@ handleSync(FastOS_FileInterface &file)
 }
 
 string
-handleWriteError(const char *text,
-                 FastOS_FileInterface &file,
-                 int64_t lastKnownGoodPos,
-                 const Packet::Entry &entry,
-                 int bufLen)
+handleWriteError(const char *text, FastOS_FileInterface &file, int64_t lastKnownGoodPos,
+                 SerialNumRange range, int bufLen)
 {
     string last(FastOS_File::getLastErrorString());
-    string e(make_string("%s. File '%s' at position %" PRId64 " for entry %" PRIu64 " of length %u. "
-                         "OS says '%s'. Rewind to last known good position %" PRId64 ".",
-                         text, file.GetFileName(), file.GetPosition(), entry.serial(), bufLen,
+    string e(make_string("%s. File '%s' at position %" PRId64 " for entries [%zu, %zu] of length %u. "
+                         "OS says '%s'. Rewind to last known good position %zu.",
+                         text, file.GetFileName(), file.GetPosition(), range.from(), range.to(), bufLen,
                          last.c_str(), lastKnownGoodPos));
     LOG(error, "%s",  e.c_str());
     if ( ! file.SetPosition(lastKnownGoodPos) ) {
         last = FastOS_File::getLastErrorString();
-        throw runtime_error(make_string("Failed setting position %" PRId64 " of file '%s' of size %" PRId64 ": OS says '%s'",
+        throw runtime_error(make_string("Failed setting position %zu of file '%s' of size %zd : OS says '%s'",
                                         lastKnownGoodPos, file.GetFileName(), file.GetSize(), last.c_str()));
     }
     handleSync(file);
@@ -118,12 +103,8 @@ tailOfFileIsZero(FastOS_FileInterface &file, int64_t lastKnownGoodPos)
 }
 
 bool
-handleReadError(const char *text,
-                FastOS_FileInterface &file,
-                ssize_t len,
-                ssize_t rlen,
-                int64_t lastKnownGoodPos,
-                bool allowTruncate)
+handleReadError(const char *text, FastOS_FileInterface &file, ssize_t len, ssize_t rlen,
+                int64_t lastKnownGoodPos, bool allowTruncate)
 {
     bool retval(true);
     if (rlen != -1) {
@@ -178,6 +159,43 @@ handleReadError(const char *text,
 
 }
 
+Packet
+DomainPart::readPacket(FastOS_FileInterface & transLog, SerialNumRange wanted, size_t targetSize, bool allowTruncate) {
+    Alloc buf;
+    Packet packet(targetSize);
+    int64_t fSize(transLog.GetSize());
+    int64_t currPos(transLog.GetPosition());
+    for(size_t i(0); (packet.sizeBytes() < targetSize) && (currPos < fSize) && (packet.range().to() < wanted.to()); i++) {
+        IChunk::UP chunk;
+        if (read(transLog, chunk, buf, allowTruncate)) {
+            if (chunk) {
+                try {
+                    for (const Packet::Entry & e : chunk->getEntries()) {
+                        if ((wanted.from() < e.serial()) && (e.serial() <= wanted.to())) {
+                            addPacket(packet, e);
+                        }
+                    }
+                } catch (const std::exception & ex) {
+                    throw runtime_error(make_string("%s : Failed creating packet for list %s(%" PRIu64 ") at pos(%" PRIu64 ", %" PRIu64 ")",
+                                                    ex.what(), transLog.GetFileName(), fSize, currPos, transLog.GetPosition()));
+                }
+            } else {
+                throw runtime_error(make_string("Invalid entry reading file %s(%" PRIu64 ") at pos(%" PRIu64 ", %" PRIu64 ")",
+                                                transLog.GetFileName(), fSize, currPos, transLog.GetPosition()));
+            }
+        } else {
+            if (transLog.GetSize() != fSize) {
+                fSize = transLog.GetSize();
+            } else {
+                throw runtime_error(make_string("Failed reading file %s(%" PRIu64 ") at pos(%" PRIu64 ", %" PRIu64 ")",
+                                                transLog.GetFileName(), fSize, currPos, transLog.GetPosition()));
+            }
+        }
+        currPos = transLog.GetPosition();
+    }
+    return packet;
+}
+
 int64_t
 DomainPart::buildPacketMapping(bool allowTruncate)
 {
@@ -208,66 +226,35 @@ DomainPart::buildPacketMapping(bool allowTruncate)
             handleReadError("file header", transLog, 0, FileHeader::getMinSize(), 0, allowTruncate);
         }
     }
+    const SerialNumRange all(0, std::numeric_limits<SerialNum>::max());
     while ((currPos < fSize)) {
-        Packet packet;
-        SerialNum firstSerial(0);
-        SerialNum lastSerial(0);
-        int64_t firstPos(currPos);
-        bool full(false);
-        Alloc buf;
-        for(size_t i(0); !full && (currPos < fSize); i++) {
-            Packet::Entry e;
-            if (read(transLog, e, buf, allowTruncate)) {
-                if (e.valid()) {
-                    if (i == 0) {
-                        firstSerial = e.serial();
-                        if (currPos == _headerLen) {
-                            _range.from(firstSerial);
-                        }
-                    }
-                    try {
-                        full = addPacket(packet, e);
-                        if ( ! full ) {
-                            lastSerial = e.serial();
-                            currPos = transLog.GetPosition();
-                            _sz++;
-                        } else {
-                            transLog.SetPosition(currPos);
-                        }
-                    } catch (const std::exception & ex) {
-                        throw runtime_error(make_string("%s : Failed creating packet for list %s(%" PRIu64 ") at pos(%" PRIu64 ", %" PRIu64 ")",
-                                                    ex.what(), transLog.GetFileName(), fSize, currPos, transLog.GetPosition()));
-                    }
-                } else {
-                    throw runtime_error(make_string("Invalid entry reading file %s(%" PRIu64 ") at pos(%" PRIu64 ", %" PRIu64 ")",
-                                                transLog.GetFileName(), fSize, currPos, transLog.GetPosition()));
-                }
-            } else {
-                if (transLog.GetSize() != fSize) {
-                    fSize = transLog.GetSize();
-                } else {
-                    throw runtime_error(make_string("Failed reading file %s(%" PRIu64 ") at pos(%" PRIu64 ", %" PRIu64 ")",
-                                                transLog.GetFileName(), fSize, currPos, transLog.GetPosition()));
-                }
-            }
-        }
-        packet.close();
+        const int64_t firstPos(currPos);
+        Packet packet = readPacket(transLog, all, TARGET_PACKET_SIZE, allowTruncate);
         if (!packet.empty()) {
-            _packets[firstSerial] = packet;
-            _range.to(lastSerial);
+            _sz += packet.size();
+            const SerialNum firstSerial = packet.range().from();
+            if (currPos == _headerLen) {
+                _range.from(firstSerial);
+            }
+            _range.to(packet.range().to());
+            _packets.insert(std::make_pair(firstSerial, std::move(packet)));
             {
                 LockGuard guard(_lock);
                 _skipList.push_back(SkipInfo(firstSerial, firstPos));
             }
+        } else {
+            fSize = transLog.GetSize();
         }
+        currPos = transLog.GetPosition();
     }
     transLog.Close();
     return currPos;
 }
 
-DomainPart::DomainPart(const string & name, const string & baseDir, SerialNum s, Crc defaultCrc,
-                       const FileHeaderContext &fileHeaderContext, bool allowTruncate) :
-    _defaultCrc(defaultCrc),
+DomainPart::DomainPart(const string & name, const string & baseDir, SerialNum s, Encoding encoding,
+                       uint8_t compressionLevel, const FileHeaderContext &fileHeaderContext, bool allowTruncate) :
+    _encoding(encoding),
+    _compressionLevel(compressionLevel),
     _lock(),
     _fileLock(),
     _range(s),
@@ -411,10 +398,12 @@ DomainPart::commit(SerialNum firstSerial, const Packet &packet)
         //LOG(spam,
         //"Pos(%d) Len(%d), Lim(%d), Remaining(%d)",
         //h.getPos(), h.getLength(), h.getLimit(), h.getRemaining());
+        IChunk::UP chunk = IChunk::create(_encoding, _compressionLevel);
         Packet::Entry entry;
         entry.deserialize(h);
         if (_range.to() < entry.serial()) {
-            write(*_transLog, entry);
+            chunk->add(entry);
+            write(*_transLog, *chunk);
             _sz++;
             _range.to(entry.serial());
         } else {
@@ -428,17 +417,15 @@ DomainPart::commit(SerialNum firstSerial, const Packet &packet)
     if ( ! _packets.empty() ) {
         Packet & lastPacket = _packets.rbegin()->second;
         if (lastPacket.sizeBytes() < 0xf000) {
-            if ( ! (merged = lastPacket.merge(packet)) ) {
-                LOG(error, "Failed merging packet [%" PRIu64 ", %" PRIu64 "] with [%" PRIu64 ", %" PRIu64 "]",
-                           lastPacket.range().from(), lastPacket.range().to(),
-                           packet.range().from(), packet.range().to());
-            }
+            lastPacket.merge(packet);
+            merged = true;
         }
     }
     if (! merged ) {
-        _packets[firstSerial] = packet;
+        _packets.insert(std::make_pair(firstSerial, std::move(packet)));
         _skipList.push_back(SkipInfo(firstSerial, firstPos));
     }
+    sync();
 }
 
 void DomainPart::sync()
@@ -506,23 +493,17 @@ DomainPart::visit(SerialNumRange &r, Packet &packet)
                         if (e.serial() <= r.to()) {
                             LOG(spam, "Adding serial #%" PRIu64 ", of type %d and size %zd into packet of size %zu and %zu bytes",
                                       e.serial(), e.type(), e.data().size(), newPacket.size(), newPacket.sizeBytes());
-                            if (newPacket.add(e)) {
-                                r.from(e.serial());
-                            } else {
-                                throw runtime_error("Could not add entry to packet. Here is some mumbo jumbo. Fix.");
-                            }
+                            newPacket.add(e);
+                            r.from(e.serial());
                         } else {
                             // Force breakout on visiting empty interval.
                             r.from(r.to());
                         }
                     }
                 }
-                newPacket.close();
-                packet = newPacket;
+                packet = std::move(newPacket);
                 retval = next != _packets.end();
             }
-        } else {
-            packet.close();
         }
     } else {
         /// File has been closed must continue from file.
@@ -539,131 +520,86 @@ DomainPart::visit(FastOS_FileInterface &file, SerialNumRange &r, Packet &packet)
     if ( ! file.IsOpened() ) {
         retval = openAndFind(file, r.from() + 1);
     }
-    if (retval) {
-        Packet newPacket;
-        Alloc buf;
-        for (bool full(false);!full && retval && (r.from() < r.to());) {
-            Packet::Entry e;
-            int64_t fPos = file.GetPosition();
-            retval = read(file, e, buf, false);
-            if (retval &&
-                e.valid() &&
-                (r.from() < e.serial()) &&
-                (e.serial() <= r.to())) {
-                try {
-                    full = addPacket(newPacket, e);
-                } catch (const std::exception & ex) {
-                    throw runtime_error(make_string("%s : Failed creating packet for visit %s(%" PRIu64 ") at pos(%" PRIu64 ", %" PRIu64 ")",
-                                                    ex.what(), file.GetFileName(), file.GetSize(), fPos, file.GetPosition()));
-                }
-                if ( !full ) {
-                    r.from(e.serial());
-                } else {
-                    if ( ! file.SetPosition(fPos) ) {
-                        throw runtime_error(make_string("Failed setting read position for file '%s' of size %" PRId64 " from %" PRId64 " to %" PRId64 ".",
-                                                        file.GetFileName(), file.GetSize(), file.GetPosition(), fPos));
-                    }
-                }
-            }
-        }
-        newPacket.close();
-        packet = newPacket;
+    if ( ! retval) {
+        return false;
     }
 
-    return retval;
+    packet = readPacket(file, r, TARGET_PACKET_SIZE, false);
+    if (!packet.empty()) {
+        r.from(packet.range().to());
+    }
+
+    return !packet.empty();
 }
 
 void
-DomainPart::write(FastOS_FileInterface &file, const Packet::Entry &entry)
+DomainPart::write(FastOS_FileInterface &file, const IChunk & chunk)
 {
-    int64_t lastKnownGoodPos(file.GetPosition());
-    int32_t crc(0);
-    uint32_t len(entry.serializedSize() + sizeof(crc));
     nbostream os;
-    os << static_cast<uint8_t>(_defaultCrc);
-    os << len;
-    size_t start(os.size());
-    entry.serialize(os);
-    size_t end(os.size());
-    crc = calcCrc(_defaultCrc, os.c_str()+start, end - start);
-    os << crc;
-    size_t osSize = os.size();
-    assert(osSize == len + sizeof(len) + sizeof(uint8_t));
+    size_t begin = os.wp();
+    os << _encoding.getRaw();
+    os << uint32_t(0);
+    Encoding realEncoding = chunk.encode(os);
+    size_t end = os.wp();
+    os.wp(0);
+    os << realEncoding.getRaw();
+    os << uint32_t(end - (begin + sizeof(uint32_t) + sizeof(uint8_t)));
+    os.wp(end);
+    int64_t lastKnownGoodPos(file.GetPosition());
 
     LockGuard guard(_writeLock);
-    if ( ! file.CheckedWrite(os.c_str(), osSize) ) {
-        throw runtime_error(handleWriteError("Failed writing the entry.", file, lastKnownGoodPos, entry, end - start));
+    if ( ! file.CheckedWrite(os.c_str(), os.size()) ) {
+        throw runtime_error(handleWriteError("Failed writing the entry.", file, lastKnownGoodPos, chunk.range(), os.size()));
     }
-    _writtenSerial = entry.serial();
-    _byteSize.store(lastKnownGoodPos + osSize, std::memory_order_release);
+    _writtenSerial = chunk.range().to();
+    _byteSize.store(lastKnownGoodPos + os.size(), std::memory_order_release);
 }
 
 bool
-DomainPart::read(FastOS_FileInterface &file,
-                 Packet::Entry &entry,
-                 Alloc & buf,
-                 bool allowTruncate)
+DomainPart::read(FastOS_FileInterface &file, IChunk::UP & chunk, Alloc & buf, bool allowTruncate)
 {
-    bool retval(true);
     char tmp[5];
     int64_t lastKnownGoodPos(file.GetPosition());
     size_t rlen = file.Read(tmp, sizeof(tmp));
     nbostream his(tmp, sizeof(tmp));
-    uint8_t version(-1);
+    uint8_t encoding(-1);
     uint32_t len(0);
-    his >> version >> len;
-    if ((retval = (rlen == sizeof(tmp)))) {
-        if ( ! (retval = (version == ccitt_crc32) || version == xxh64)) {
-            string msg(make_string("Version mismatch. Expected 'ccitt_crc32=1' or 'xxh64=2',"
-                                             " got %d from '%s' at position %ld",
-                                             version, file.GetFileName(), lastKnownGoodPos));
-            if ((version == 0) && (len == 0) && tailOfFileIsZero(file, lastKnownGoodPos)) {
-                LOG(warning, "%s", msg.c_str());
-                return handleReadError("packet version", file, sizeof(tmp), rlen, lastKnownGoodPos, allowTruncate);
-            } else {
-                throw runtime_error(msg);
-            }
-        }
-        if (len > buf.size()) {
-            Alloc::alloc(len).swap(buf);
-        }
-        rlen = file.Read(buf.get(), len);
-        retval = rlen == len;
-        if (!retval) {
-            retval = handleReadError("packet blob", file, len, rlen, lastKnownGoodPos, allowTruncate);
-        } else {
-            nbostream_longlivedbuf is(buf.get(), len);
-            entry.deserialize(is);
-            int32_t crc(0);
-            is >> crc;
-            int32_t crcVerify(calcCrc(static_cast<Crc>(version), buf.get(), len - sizeof(crc)));
-            if (crc != crcVerify) {
-                throw runtime_error(make_string("Got bad crc for packet from '%s' (len pos=%" PRId64 ", len=%d) : crcVerify = %d, expected %d",
-                                                file.GetFileName(), file.GetPosition() - len - sizeof(len),
-                                                static_cast<int>(len), static_cast<int>(crcVerify), static_cast<int>(crc)));
-            }
-        }
-    } else {
-        if (rlen == 0) {
-           // Eof
+    his >> encoding >> len;
+    if (rlen != sizeof(tmp)) {
+        return (rlen == 0)
+               ? true
+               : handleReadError("packet length", file, sizeof(len), rlen, lastKnownGoodPos, allowTruncate);
+    }
+
+    try {
+        chunk = IChunk::create(encoding);
+    } catch (const std::exception & e) {
+        string msg(make_string("Version mismatch. Expected 'ccitt_crc32=1' or 'xxh64=2',"
+                               " got %d from '%s' at position %ld",
+                               encoding, file.GetFileName(), lastKnownGoodPos));
+        if ((encoding == 0) && (len == 0) && tailOfFileIsZero(file, lastKnownGoodPos)) {
+            LOG(warning, "%s", msg.c_str());
+            return handleReadError("packet version", file, sizeof(tmp), rlen, lastKnownGoodPos, allowTruncate);
         } else {
-           retval = handleReadError("packet length", file, sizeof(len), rlen, lastKnownGoodPos, allowTruncate);
+            throw runtime_error(msg);
         }
     }
-    return retval;
-}
-
-int32_t DomainPart::calcCrc(Crc version, const void * buf, size_t sz)
-{
-    if (version == xxh64) {
-        return static_cast<int32_t>(XXH64(buf, sz, 0ll));
-    } else if (version == ccitt_crc32) {
-        vespalib::crc_32_type calculator;
-        calculator.process_bytes(buf, sz);
-        return calculator.checksum();
-    } else {
-        abort();
+    if (len > buf.size()) {
+        Alloc::alloc(len).swap(buf);
     }
+    rlen = file.Read(buf.get(), len);
+    if (rlen != len) {
+        return handleReadError("packet blob", file, len, rlen, lastKnownGoodPos, allowTruncate);
+    }
+    try {
+        nbostream_longlivedbuf is(buf.get(), len);
+        chunk->decode(is);
+    } catch (const std::exception & e) {
+        throw runtime_error(make_string("Got exception during decoding of packet '%s' from file '%s' (len pos=%" PRId64 ", len=%d)",
+                            e.what(), file.GetFileName(), file.GetPosition() - len - sizeof(len), static_cast<int>(len)));
+    }
+
+    return true;
 }
 
 }
diff --git a/searchlib/src/vespa/searchlib/transactionlog/domainpart.h b/searchlib/src/vespa/searchlib/transactionlog/domainpart.h
index 59d0df6df94..5256b731125 100644
--- a/searchlib/src/vespa/searchlib/transactionlog/domainpart.h
+++ b/searchlib/src/vespa/searchlib/transactionlog/domainpart.h
@@ -2,6 +2,7 @@
 #pragma once
 
 #include "common.h"
+#include "ichunk.h"
 #include <vespa/vespalib/util/sync.h>
 #include <vespa/vespalib/util/memory.h>
 #include <map>
@@ -19,13 +20,9 @@ private:
     DomainPart& operator=(const DomainPart &);
 
 public:
-    enum Crc {
-        ccitt_crc32=1,
-        xxh64=2
-    };
     typedef std::shared_ptr<DomainPart> SP;
-    DomainPart(const vespalib::string &name, const vespalib::string &baseDir, SerialNum s, Crc defaultCrc,
-               const common::FileHeaderContext &FileHeaderContext, bool allowTruncate);
+    DomainPart(const vespalib::string &name, const vespalib::string &baseDir, SerialNum s, Encoding defaultEncoding,
+               uint8_t compressionLevel, const common::FileHeaderContext &FileHeaderContext, bool allowTruncate);
 
     ~DomainPart();
 
@@ -49,13 +46,13 @@ public:
     }
     bool        isClosed() const;
 private:
+    using Alloc = vespalib::alloc::Alloc;
     bool openAndFind(FastOS_FileInterface &file, const SerialNum &from);
     int64_t buildPacketMapping(bool allowTruncate);
+    static Packet readPacket(FastOS_FileInterface & file, SerialNumRange wanted, size_t targetSize, bool allowTruncate);
+    static bool read(FastOS_FileInterface &file, IChunk::UP & chunk, Alloc &buf, bool allowTruncate);
 
-    static bool read(FastOS_FileInterface &file, Packet::Entry &entry, vespalib::alloc::Alloc &buf, bool allowTruncate);
-
-    void write(FastOS_FileInterface &file, const Packet::Entry &entry);
-    static int32_t calcCrc(Crc crc, const void * buf, size_t len);
+    void write(FastOS_FileInterface &file, const IChunk & entry);
     void writeHeader(const common::FileHeaderContext &fileHeaderContext);
 
     class SkipInfo
@@ -77,21 +74,22 @@ private:
     };
     typedef std::vector<SkipInfo> SkipList;
     typedef std::map<SerialNum, Packet> PacketList;
-    const Crc      _defaultCrc;
-    vespalib::Lock _lock;
-    vespalib::Lock _fileLock;
-    SerialNumRange _range;
-    size_t         _sz;
+    const Encoding        _encoding;
+    const uint8_t         _compressionLevel;
+    vespalib::Lock        _lock;
+    vespalib::Lock        _fileLock;
+    SerialNumRange        _range;
+    size_t                _sz;
     std::atomic<uint64_t> _byteSize;
-    PacketList     _packets;
-    vespalib::string _fileName;
+    PacketList            _packets;
+    vespalib::string      _fileName;
     std::unique_ptr<FastOS_FileInterface> _transLog;
-    SkipList       _skipList;
-    uint32_t       _headerLen;
-    vespalib::Lock _writeLock;
+    SkipList              _skipList;
+    uint32_t              _headerLen;
+    vespalib::Lock        _writeLock;
     // Protected by _writeLock
-    SerialNum      _writtenSerial;
-    SerialNum      _syncedSerial;
+    SerialNum             _writtenSerial;
+    SerialNum             _syncedSerial;
 };
 
 }
diff --git a/searchlib/src/vespa/searchlib/transactionlog/ichunk.cpp b/searchlib/src/vespa/searchlib/transactionlog/ichunk.cpp
new file mode 100644
index 00000000000..af7d396c0e4
--- /dev/null
+++ b/searchlib/src/vespa/searchlib/transactionlog/ichunk.cpp
@@ -0,0 +1,108 @@
+// Copyright 2017 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+
+#include "chunks.h"
+#include <vespa/vespalib/util/stringfmt.h>
+#include <vespa/vespalib/util/crc.h>
+#include <vespa/vespalib/xxhash/xxhash.h>
+#include <cassert>
+
+using std::runtime_error;
+using std::make_unique;
+using vespalib::make_string;
+using vespalib::nbostream_longlivedbuf;
+using vespalib::compression::CompressionConfig;
+
+namespace search::transactionlog {
+
+Encoding::Encoding(Crc crc, Compression compression)
+    : _raw(crc | (compression >> 2))
+{
+    assert(crc <= Crc::xxh64);
+    assert(compression <= Compression::lz4);
+}
+
+IChunk::~IChunk() = default;
+
+void
+IChunk::add(const Packet::Entry & entry) {
+    _entries.emplace_back(entry);
+}
+
+SerialNumRange
+IChunk::range() const {
+    return _entries.empty()
+           ? SerialNumRange()
+           : SerialNumRange(_entries.front().serial(), _entries.back().serial());
+}
+
+void
+IChunk::deserializeEntries(nbostream & is) {
+    while (is.good() && !is.empty()) {
+        Packet::Entry e;
+        e.deserialize(is);
+        add(e);
+    }
+}
+
+void
+IChunk::serializeEntries(nbostream & os) const {
+    for (const auto & e : _entries) {
+        e.serialize(os);
+    }
+}
+
+Encoding
+IChunk::encode(nbostream & os) const {
+    return onEncode(os);
+}
+
+void
+IChunk::decode(nbostream & is) {
+    onDecode(is);
+}
+
+IChunk::UP
+IChunk::create(uint8_t chunkType) {
+    return create(Encoding(chunkType), 9);
+}
+IChunk::UP
+IChunk::create(Encoding encoding, uint8_t compressionLevel) {
+    switch (encoding.getCrc()) {
+        case Encoding::Crc::xxh64:
+            switch (encoding.getCompression()) {
+                case Encoding::Compression::none:
+                    return make_unique<XXH64None>();
+                case Encoding::Compression::lz4:
+                    return make_unique<XXH64Compressed>(CompressionConfig::LZ4, compressionLevel);
+                case Encoding::Compression::zstd:
+                    return make_unique<XXH64Compressed>(CompressionConfig::ZSTD, compressionLevel);
+                default:
+                    return make_unique<XXH64Compressed>(CompressionConfig::LZ4, compressionLevel);
+            }
+        case Encoding::Crc::ccitt_crc32:
+            switch (encoding.getCompression()) {
+                case Encoding::Compression::none:
+                    return make_unique<CCITTCRC32None>();
+                default:
+                    throw runtime_error(make_string("Unhandled compression type '%d' for ccitt_crc32 compression",
+                                                    encoding.getCompression()));
+            }
+        default:
+            throw runtime_error(make_string("Unhandled crc type '%d'", encoding.getCrc()));
+    }
+}
+
+int32_t Encoding::calcCrc(Crc version, const void * buf, size_t sz)
+{
+    if (version == xxh64) {
+        return static_cast<int32_t>(XXH64(buf, sz, 0ll));
+    } else if (version == ccitt_crc32) {
+        vespalib::crc_32_type calculator;
+        calculator.process_bytes(buf, sz);
+        return calculator.checksum();
+    } else {
+        abort();
+    }
+}
+
+}
diff --git a/searchlib/src/vespa/searchlib/transactionlog/ichunk.h b/searchlib/src/vespa/searchlib/transactionlog/ichunk.h
new file mode 100644
index 00000000000..0e913703468
--- /dev/null
+++ b/searchlib/src/vespa/searchlib/transactionlog/ichunk.h
@@ -0,0 +1,57 @@
+// Copyright 2017 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+
+#pragma once
+
+#include "common.h"
+#include <memory>
+
+namespace vespalib { class nbostream; }
+
+namespace search::transactionlog {
+
+class Encoding {
+public:
+    enum Crc {
+        nocrc = 0,
+        ccitt_crc32 = 1,
+        xxh64 = 2
+    };
+    enum Compression {
+        none = 0,
+        lz4 = 1,
+        zstd = 2
+    };
+    Encoding(uint8_t raw) : _raw(raw) {}
+    Encoding(Crc crc, Compression compression);
+    Crc getCrc() const { return Crc(_raw & 0x3); }
+    Compression getCompression() const { return Compression((_raw >> 2) & 0xf); }
+    static int32_t calcCrc(Crc version, const void * buf, size_t sz);
+    uint8_t getRaw() const { return _raw; }
+private:
+    uint8_t _raw;
+};
+
+class IChunk {
+public:
+    using UP = std::unique_ptr<IChunk>;
+    using Entries = std::vector<Packet::Entry>;
+    using nbostream = vespalib::nbostream;
+    using ConstBufferRef = vespalib::ConstBufferRef;
+    virtual ~IChunk();
+    const Entries & getEntries() const { return _entries; }
+    void add(const Packet::Entry & entry);
+    Encoding encode(nbostream & os) const;
+    void decode(nbostream & buf);
+    static UP create(uint8_t chunkType);
+    static UP create(Encoding chunkType, uint8_t compressionLevel);
+    SerialNumRange range() const;
+protected:
+    virtual Encoding onEncode(nbostream & os) const = 0;
+    virtual void onDecode(nbostream & is) = 0;
+    void deserializeEntries(nbostream & is);
+    void serializeEntries(nbostream & os) const;
+private:
+    Entries _entries;
+};
+
+}
diff --git a/searchlib/src/vespa/searchlib/transactionlog/session.cpp b/searchlib/src/vespa/searchlib/transactionlog/session.cpp
index cbcbc68fdff..56aaa162485 100644
--- a/searchlib/src/vespa/searchlib/transactionlog/session.cpp
+++ b/searchlib/src/vespa/searchlib/transactionlog/session.cpp
@@ -36,7 +36,7 @@ Session::VisitTask::run()
 
 bool
 Session::visit(FastOS_FileInterface & file, DomainPart & dp) {
-    Packet packet;
+    Packet packet(size_t(-1));
     bool more(false);
     if (dp.isClosed()) {
         more = dp.visit(file, _range, packet);
diff --git a/searchlib/src/vespa/searchlib/transactionlog/translogserver.cpp b/searchlib/src/vespa/searchlib/transactionlog/translogserver.cpp
index 4c3c5609a93..f724f5035c8 100644
--- a/searchlib/src/vespa/searchlib/transactionlog/translogserver.cpp
+++ b/searchlib/src/vespa/searchlib/transactionlog/translogserver.cpp
@@ -1,5 +1,6 @@
 // Copyright 2017 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
 #include "translogserver.h"
+#include <vespa/searchlib/common/gatecallback.h>
 #include <vespa/vespalib/util/stringfmt.h>
 #include <vespa/vespalib/io/fileutil.h>
 #include <vespa/vespalib/util/exceptions.h>
@@ -13,6 +14,9 @@ using vespalib::make_string;
 using vespalib::stringref;
 using vespalib::IllegalArgumentException;
 using search::common::FileHeaderContext;
+using std::make_shared;
+using std::runtime_error;
+using namespace std::chrono_literals;
 
 namespace search::transactionlog {
 
@@ -26,21 +30,16 @@ class SyncHandler : public FNET_Task
     SerialNum                   _syncTo;
     
 public:
-    SyncHandler(FRT_Supervisor *supervisor,
-                FRT_RPCRequest *req,const Domain::SP &domain,
-                const TransLogServer::Session::SP &session,
-                SerialNum syncTo);
+    SyncHandler(FRT_Supervisor *supervisor, FRT_RPCRequest *req,const Domain::SP &domain,
+                const TransLogServer::Session::SP &session, SerialNum syncTo);
 
     ~SyncHandler();
     void PerformTask() override;
 };
 
 
-SyncHandler::SyncHandler(FRT_Supervisor *supervisor,
-                         FRT_RPCRequest *req,
-                         const Domain::SP &domain,
-                         const TransLogServer::Session::SP &session,
-                         SerialNum syncTo)
+SyncHandler::SyncHandler(FRT_Supervisor *supervisor, FRT_RPCRequest *req, const Domain::SP &domain,
+                         const TransLogServer::Session::SP &session, SerialNum syncTo)
     : FNET_Task(supervisor->GetScheduler()),
       _req(*req),
       _domain(domain),
@@ -50,9 +49,7 @@ SyncHandler::SyncHandler(FRT_Supervisor *supervisor,
 }
 
 
-SyncHandler::~SyncHandler()
-{
-}
+SyncHandler::~SyncHandler() = default;
 
 
 void
@@ -77,25 +74,25 @@ SyncHandler::PerformTask()
 
 TransLogServer::TransLogServer(const vespalib::string &name, int listenPort, const vespalib::string &baseDir,
                                const FileHeaderContext &fileHeaderContext)
-    : TransLogServer(name, listenPort, baseDir, fileHeaderContext, 0x10000000)
+    : TransLogServer(name, listenPort, baseDir, fileHeaderContext,
+                     DomainConfig().setEncoding(Encoding(Encoding::xxh64, Encoding::Compression::none))
+                             .setPartSizeLimit(0x10000000).setChunkSizeLimit(0x40000).setChunkAgeLimit( 1ms))
 {}
 
 TransLogServer::TransLogServer(const vespalib::string &name, int listenPort, const vespalib::string &baseDir,
-                               const FileHeaderContext &fileHeaderContext, uint64_t domainPartSize)
-    : TransLogServer(name, listenPort, baseDir, fileHeaderContext, domainPartSize, 4, DomainPart::Crc::xxh64)
+                               const FileHeaderContext &fileHeaderContext, const DomainConfig & cfg)
+    : TransLogServer(name, listenPort, baseDir, fileHeaderContext, cfg, 4)
 {}
 
 TransLogServer::TransLogServer(const vespalib::string &name, int listenPort, const vespalib::string &baseDir,
-                               const FileHeaderContext &fileHeaderContext, uint64_t domainPartSize,
-                               size_t maxThreads, DomainPart::Crc defaultCrcType)
+                               const FileHeaderContext &fileHeaderContext, const DomainConfig & cfg, size_t maxThreads)
     : FRT_Invokable(),
       _name(name),
       _baseDir(baseDir),
-      _domainPartSize(domainPartSize),
-      _defaultCrcType(defaultCrcType),
+      _domainConfig(cfg),
       _commitExecutor(maxThreads, 128*1024),
       _sessionExecutor(maxThreads, 128*1024),
-      _threadPool(8192, 1),
+      _threadPool(0x20000),
       _supervisor(std::make_unique<FRT_Supervisor>()),
       _domains(),
       _reqQ(),
@@ -110,8 +107,8 @@ TransLogServer::TransLogServer(const vespalib::string &name, int listenPort, con
                 domainDir >> domainName;
                 if ( ! domainName.empty()) {
                     try {
-                        auto domain = std::make_shared<Domain>(domainName, dir(), _commitExecutor, _sessionExecutor,
-                                                               _domainPartSize, _defaultCrcType,_fileHeaderContext);
+                        auto domain = make_shared<Domain>(domainName, dir(), _threadPool, _commitExecutor,
+                                                          _sessionExecutor, cfg,_fileHeaderContext);
                         _domains[domain->name()] = domain;
                     } catch (const std::exception & e) {
                         LOG(warning, "Failed creating %s domain on startup. Exception = %s", domainName.c_str(), e.what());
@@ -132,13 +129,13 @@ TransLogServer::TransLogServer(const vespalib::string &name, int listenPort, con
                 }
             }
             if ( ! listenOk ) {
-                throw std::runtime_error(make_string("Failed listening at port %s. Giving up. Requires manual intervention.", listenSpec));
+                throw runtime_error(make_string("Failed listening at port %s. Giving up. Requires manual intervention.", listenSpec));
             }
         } else {
-            throw std::runtime_error(make_string("Failed creating tls dir %s r(%d), e(%d). Requires manual intervention.", dir().c_str(), retval, errno));
+            throw runtime_error(make_string("Failed creating tls dir %s r(%d), e(%d). Requires manual intervention.", dir().c_str(), retval, errno));
         }
     } else {
-        throw std::runtime_error(make_string("Failed creating tls base dir %s r(%d), e(%d). Requires manual intervention.", _baseDir.c_str(), retval, errno));
+        throw runtime_error(make_string("Failed creating tls base dir %s r(%d), e(%d). Requires manual intervention.", _baseDir.c_str(), retval, errno));
     }
     start(_threadPool);
 }
@@ -200,7 +197,7 @@ void TransLogServer::run()
             }
         }
         logMetric();
-    } while (running() && !(hasPacket && (req == NULL)));
+    } while (running() && !(hasPacket && (req == nullptr)));
     LOG(info, "TLS Stopped");
 }
 
@@ -215,6 +212,17 @@ void TransLogServer::logMetric() const
     }
 }
 
+
+TransLogServer &
+TransLogServer::setDomainConfig(const DomainConfig & cfg) {
+    Guard domainGuard(_lock);
+    _domainConfig = cfg;
+    for(auto &domain: _domains) {
+        domain.second->setConfig(cfg);
+    }
+    return *this;
+}
+
 DomainStats
 TransLogServer::getDomainStats() const
 {
@@ -349,8 +357,8 @@ void TransLogServer::createDomain(FRT_RPCRequest *req)
     Domain::SP domain(findDomain(domainName));
     if ( !domain ) {
         try {
-            domain = std::make_shared<Domain>(domainName, dir(), _commitExecutor, _sessionExecutor,
-                                              _domainPartSize, _defaultCrcType, _fileHeaderContext);
+            domain = make_shared<Domain>(domainName, dir(), _threadPool, _commitExecutor,
+                                         _sessionExecutor, _domainConfig, _fileHeaderContext);
             {
                 Guard domainGuard(_lock);
                 _domains[domain->name()] = domain;
@@ -462,7 +470,7 @@ void TransLogServer::commit(const vespalib::string & domainName, const Packet &
     (void) done;
     Domain::SP domain(findDomain(domainName));
     if (domain) {
-        domain->commit(packet);
+        domain->commit(packet, std::move(done));
     } else {
         throw IllegalArgumentException("Could not find domain " + domainName);
     }
@@ -478,7 +486,9 @@ void TransLogServer::domainCommit(FRT_RPCRequest *req)
     if (domain) {
         Packet packet(params[1]._data._buf, params[1]._data._len);
         try {
-            domain->commit(packet);
+            vespalib::Gate gate;
+            domain->commit(packet, make_shared<GateCallback>(gate));
+            gate.await();
             ret.AddInt32(0);
             ret.AddString("ok");
         } catch (const std::exception & e) {
diff --git a/searchlib/src/vespa/searchlib/transactionlog/translogserver.h b/searchlib/src/vespa/searchlib/transactionlog/translogserver.h
index d78d3d39887..83627d2d3e3 100644
--- a/searchlib/src/vespa/searchlib/transactionlog/translogserver.h
+++ b/searchlib/src/vespa/searchlib/transactionlog/translogserver.h
@@ -22,16 +22,15 @@ public:
     typedef std::shared_ptr<TransLogServer> SP;
 
     TransLogServer(const vespalib::string &name, int listenPort, const vespalib::string &baseDir,
-                   const common::FileHeaderContext &fileHeaderContext,
-                   uint64_t domainPartSize, size_t maxThreads, DomainPart::Crc defaultCrc);
+                   const common::FileHeaderContext &fileHeaderContext, const DomainConfig & cfg, size_t maxThreads);
     TransLogServer(const vespalib::string &name, int listenPort, const vespalib::string &baseDir,
-                   const common::FileHeaderContext &fileHeaderContext, uint64_t domainPartSize);
+                   const common::FileHeaderContext &fileHeaderContext, const DomainConfig & cfg);
     TransLogServer(const vespalib::string &name, int listenPort, const vespalib::string &baseDir,
                    const common::FileHeaderContext &fileHeaderContext);
     ~TransLogServer() override;
     DomainStats getDomainStats() const;
-
     void commit(const vespalib::string & domainName, const Packet & packet, DoneCallback done) override;
+    TransLogServer & setDomainConfig(const DomainConfig & cfg);
 
     class Session
     {
@@ -79,8 +78,7 @@ private:
 
     vespalib::string                    _name;
     vespalib::string                    _baseDir;
-    const uint64_t                      _domainPartSize;
-    const DomainPart::Crc               _defaultCrcType;
+    DomainConfig                        _domainConfig;
     vespalib::ThreadStackExecutor       _commitExecutor;
     vespalib::ThreadStackExecutor       _sessionExecutor;
     FastOS_ThreadPool                   _threadPool;
diff --git a/searchlib/src/vespa/searchlib/transactionlog/translogserverapp.cpp b/searchlib/src/vespa/searchlib/transactionlog/translogserverapp.cpp
index ff4a402b438..de3d72331d6 100644
--- a/searchlib/src/vespa/searchlib/transactionlog/translogserverapp.cpp
+++ b/searchlib/src/vespa/searchlib/transactionlog/translogserverapp.cpp
@@ -7,12 +7,17 @@
 LOG_SETUP(".translogserverapp");
 
 using search::common::FileHeaderContext;
+using namespace std::chrono_literals;
 
 namespace search::transactionlog {
 
+using LockGuard = std::lock_guard<std::mutex>;
+using std::make_unique;
+
 TransLogServerApp::TransLogServerApp(const config::ConfigUri & tlsConfigUri,
                                      const FileHeaderContext & fileHeaderContext)
-    : _tls(),
+    : _lock(),
+      _tls(),
       _tlsConfig(),
       _tlsConfigFetcher(tlsConfigUri.getContext()),
       _fileHeaderContext(fileHeaderContext)
@@ -23,24 +28,58 @@ TransLogServerApp::TransLogServerApp(const config::ConfigUri & tlsConfigUri,
 
 namespace {
 
-DomainPart::Crc getCrc(searchlib::TranslogserverConfig::Crcmethod crcType)
+
+Encoding::Crc
+getCrc(searchlib::TranslogserverConfig::Crcmethod type)
 {
-    switch (crcType) {
+    switch (type) {
         case searchlib::TranslogserverConfig::ccitt_crc32:
-            return DomainPart::ccitt_crc32;
+            return Encoding::Crc::ccitt_crc32;
         case searchlib::TranslogserverConfig::xxh64:
-            return DomainPart::xxh64;
+            return Encoding::Crc::xxh64;
+    }
+    return Encoding::Crc::xxh64;
+}
+
+Encoding::Compression
+getCompression(searchlib::TranslogserverConfig::Compression::Type type)
+{
+    switch (type) {
+        case searchlib::TranslogserverConfig::Compression::NONE:
+            return Encoding::Compression::none;
+        case searchlib::TranslogserverConfig::Compression::LZ4:
+            return Encoding::Compression::lz4;
+        case searchlib::TranslogserverConfig::Compression::ZSTD:
+            return Encoding::Compression::zstd;
     }
-    abort();
+    return Encoding::Compression::lz4;
+}
+
+Encoding
+getEncoding(const searchlib::TranslogserverConfig & cfg)
+{
+    return Encoding(getCrc(cfg.crcmethod), getCompression(cfg.compression.type));
+}
+
+DomainConfig
+getDomainConfig(const searchlib::TranslogserverConfig & cfg) {
+    DomainConfig dcfg;
+    dcfg.setEncoding(getEncoding(cfg))
+        .setCompressionLevel(cfg.compression.level)
+        .setPartSizeLimit(cfg.filesizemax)
+        .setChunkSizeLimit(cfg.chunk.sizelimit)
+        .setChunkAgeLimit(std::chrono::microseconds(int64_t(cfg.chunk.agelimit*1000000)));
+    return dcfg;
 }
 
 }
 
 void TransLogServerApp::start()
 {
-    std::shared_ptr<searchlib::TranslogserverConfig> c = _tlsConfig.get();
-    _tls.reset(new TransLogServer(c->servername, c->listenport, c->basedir, _fileHeaderContext,
-                                  c->filesizemax, c->maxthreads, getCrc(c->crcmethod)));
+    LockGuard guard(_lock);
+    auto c = _tlsConfig.get();
+    _tls = make_unique<TransLogServer>(c->servername, c->listenport, c->basedir, _fileHeaderContext,
+                                       getDomainConfig(*c), c->maxthreads);
 }
 
 TransLogServerApp::~TransLogServerApp()
@@ -51,8 +90,12 @@ TransLogServerApp::~TransLogServerApp()
 void TransLogServerApp::configure(std::unique_ptr<searchlib::TranslogserverConfig> cfg)
 {
     LOG(config, "configure Transaction Log Server %s at port %d", cfg->servername.c_str(), cfg->listenport);
+    LockGuard guard(_lock);
     _tlsConfig.set(cfg.release());
     _tlsConfig.latch();
+    if (_tls) {
+        _tls->setDomainConfig(getDomainConfig(*cfg));
+    }
 }
 
 }
diff --git a/searchlib/src/vespa/searchlib/transactionlog/translogserverapp.h b/searchlib/src/vespa/searchlib/transactionlog/translogserverapp.h
index 35fa994d1e4..ea6d0158cec 100644
--- a/searchlib/src/vespa/searchlib/transactionlog/translogserverapp.h
+++ b/searchlib/src/vespa/searchlib/transactionlog/translogserverapp.h
@@ -14,6 +14,7 @@ namespace search::transactionlog {
 class TransLogServerApp : public config::IFetcherCallback<searchlib::TranslogserverConfig>
 {
 private:
+    std::mutex                                           _lock;
     TransLogServer::SP                                   _tls;
     vespalib::PtrHolder<searchlib::TranslogserverConfig> _tlsConfig;
     config::ConfigFetcher                                _tlsConfigFetcher;