Merge pull request #26622 from vespa-engine/revert-26616-toregge/explore-attribute-vector-in-writer-thread

Revert "Explore attribute vector in writer thread."

20 files changed, 230 insertions, 96 deletions

diff --git a/searchcore/CMakeLists.txt b/searchcore/CMakeLists.txt
index 426e577b2d2..131460b0384 100644
--- a/searchcore/CMakeLists.txt
+++ b/searchcore/CMakeLists.txt
@@ -64,6 +64,7 @@ vespa_define_module(
     src/tests/proton/attribute/attributes_state_explorer
     src/tests/proton/attribute/document_field_extractor
     src/tests/proton/attribute/document_field_populator
+    src/tests/proton/attribute/exclusive_attribute_read_accessor
     src/tests/proton/attribute/imported_attributes_context
     src/tests/proton/attribute/imported_attributes_repo
     src/tests/proton/bucketdb/bucketdb
diff --git a/searchcore/src/tests/proton/attribute/attribute_manager/attribute_manager_test.cpp b/searchcore/src/tests/proton/attribute/attribute_manager/attribute_manager_test.cpp
index 140012624c2..c9f3a1c1de8 100644
--- a/searchcore/src/tests/proton/attribute/attribute_manager/attribute_manager_test.cpp
+++ b/searchcore/src/tests/proton/attribute/attribute_manager/attribute_manager_test.cpp
@@ -5,6 +5,7 @@
 #include <vespa/searchcore/proton/attribute/attribute_manager_reconfig.h>
 #include <vespa/searchcore/proton/attribute/attribute_writer.h>
 #include <vespa/searchcore/proton/attribute/attributemanager.h>
+#include <vespa/searchcore/proton/attribute/exclusive_attribute_read_accessor.h>
 #include <vespa/searchcore/proton/attribute/imported_attributes_repo.h>
 #include <vespa/searchcore/proton/attribute/sequential_attributes_initializer.h>
 #include <vespa/searchcore/proton/bucketdb/bucket_db_owner.h>
@@ -754,6 +755,15 @@ TEST_F("require that we can call functions on all attributes via functor",
     EXPECT_EQUAL("a1,a2,a3", functor->getSortedNames());
 }
 
+TEST_F("require that we can acquire exclusive read access to attribute", Fixture)
+{
+    f.addAttribute("attr");
+    ExclusiveAttributeReadAccessor::UP attrAccessor = f._m.getExclusiveReadAccessor("attr");
+    ExclusiveAttributeReadAccessor::UP noneAccessor = f._m.getExclusiveReadAccessor("none");
+    EXPECT_TRUE(attrAccessor.get() != nullptr);
+    EXPECT_TRUE(noneAccessor.get() == nullptr);
+}
+
 TEST_F("require that imported attributes are exposed via attribute context together with regular attributes", Fixture)
 {
     f.addAttribute("attr");
diff --git a/searchcore/src/tests/proton/attribute/attributes_state_explorer/attributes_state_explorer_test.cpp b/searchcore/src/tests/proton/attribute/attributes_state_explorer/attributes_state_explorer_test.cpp
index aa4871d3a12..bcd200cfd2f 100644
--- a/searchcore/src/tests/proton/attribute/attributes_state_explorer/attributes_state_explorer_test.cpp
+++ b/searchcore/src/tests/proton/attribute/attributes_state_explorer/attributes_state_explorer_test.cpp
@@ -92,13 +92,13 @@ TEST_F(AttributesStateExplorerTest, require_that_attributes_are_exposed_as_child
 {
     StringVector children = _explorer.get_children_names();
     std::sort(children.begin(), children.end());
-    EXPECT_EQ(StringVector({"btree", "hash", "hybrid", "regular"}), children);
+    EXPECT_EQ(StringVector({"btree", "extra", "hash", "hybrid", "regular"}), children);
 }
 
 TEST_F(AttributesStateExplorerTest, require_that_attributes_are_explorable)
 {
     EXPECT_TRUE(_explorer.get_child("regular").get() != nullptr);
-    EXPECT_TRUE(_explorer.get_child("extra").get() == nullptr);
+    EXPECT_TRUE(_explorer.get_child("extra").get() != nullptr);
     EXPECT_TRUE(_explorer.get_child("not").get() == nullptr);
 }
 
diff --git a/searchcore/src/tests/proton/attribute/exclusive_attribute_read_accessor/.gitignore b/searchcore/src/tests/proton/attribute/exclusive_attribute_read_accessor/.gitignore
new file mode 100644
index 00000000000..f3666eecb6e
--- /dev/null
+++ b/searchcore/src/tests/proton/attribute/exclusive_attribute_read_accessor/.gitignore
@@ -0,0 +1 @@
+searchcore_exclusive_attribute_read_accessor_test_app
diff --git a/searchcore/src/tests/proton/attribute/exclusive_attribute_read_accessor/CMakeLists.txt b/searchcore/src/tests/proton/attribute/exclusive_attribute_read_accessor/CMakeLists.txt
new file mode 100644
index 00000000000..981d2acd7c5
--- /dev/null
+++ b/searchcore/src/tests/proton/attribute/exclusive_attribute_read_accessor/CMakeLists.txt
@@ -0,0 +1,9 @@
+# Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+vespa_add_executable(searchcore_exclusive_attribute_read_accessor_test_app TEST
+    SOURCES
+    exclusive_attribute_read_accessor_test.cpp
+    DEPENDS
+    searchcore_attribute
+    searchcore_pcommon
+)
+vespa_add_test(NAME searchcore_exclusive_attribute_read_accessor_test_app COMMAND searchcore_exclusive_attribute_read_accessor_test_app)
diff --git a/searchcore/src/tests/proton/attribute/exclusive_attribute_read_accessor/exclusive_attribute_read_accessor_test.cpp b/searchcore/src/tests/proton/attribute/exclusive_attribute_read_accessor/exclusive_attribute_read_accessor_test.cpp
new file mode 100644
index 00000000000..8b093be08b7
--- /dev/null
+++ b/searchcore/src/tests/proton/attribute/exclusive_attribute_read_accessor/exclusive_attribute_read_accessor_test.cpp
@@ -0,0 +1,55 @@
+// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+#include <vespa/vespalib/testkit/testapp.h>
+
+#include <vespa/searchcore/proton/attribute/exclusive_attribute_read_accessor.h>
+#include <vespa/searchcommon/attribute/config.h>
+#include <vespa/searchlib/attribute/attributefactory.h>
+#include <vespa/searchlib/attribute/attributevector.h>
+#include <vespa/vespalib/util/sequencedtaskexecutor.h>
+#include <vespa/vespalib/util/gate.h>
+
+using namespace proton;
+using namespace search;
+using namespace vespalib;
+
+using ReadGuard = ExclusiveAttributeReadAccessor::Guard;
+VESPA_THREAD_STACK_TAG(test_executor)
+
+AttributeVector::SP
+createAttribute()
+{
+    attribute::Config cfg(attribute::BasicType::INT32, attribute::CollectionType::SINGLE);
+    return search::AttributeFactory::createAttribute("myattr", cfg);
+}
+
+struct Fixture
+{
+    AttributeVector::SP attribute;
+    std::unique_ptr<ISequencedTaskExecutor> writer;
+    ExclusiveAttributeReadAccessor accessor;
+
+    Fixture()
+        : attribute(createAttribute()),
+          writer(SequencedTaskExecutor::create(test_executor, 1)),
+          accessor(attribute, *writer)
+    {}
+};
+
+TEST_F("require that attribute write thread is blocked while guard is held", Fixture)
+{
+    ReadGuard::UP guard = f.accessor.takeGuard();
+    Gate gate;
+    f.writer->execute(f.writer->getExecutorIdFromName(f.attribute->getNamePrefix()), [&gate]() { gate.countDown(); });
+    bool reachedZero = gate.await(100ms);
+    EXPECT_FALSE(reachedZero);
+    EXPECT_EQUAL(1u, gate.getCount());
+
+    guard.reset();
+    gate.await();
+    EXPECT_EQUAL(0u, gate.getCount());
+}
+
+TEST_MAIN()
+{
+    TEST_RUN_ALL();
+}
diff --git a/searchcore/src/vespa/searchcore/proton/attribute/CMakeLists.txt b/searchcore/src/vespa/searchcore/proton/attribute/CMakeLists.txt
index 70a91b418a9..82bb188870f 100644
--- a/searchcore/src/vespa/searchcore/proton/attribute/CMakeLists.txt
+++ b/searchcore/src/vespa/searchcore/proton/attribute/CMakeLists.txt
@@ -7,7 +7,6 @@ vespa_add_library(searchcore_attribute STATIC
     attribute_collection_spec.cpp
     attribute_config_inspector.cpp
     attribute_directory.cpp
-    attribute_executor.cpp
     attribute_factory.cpp
     attribute_initializer.cpp
     attribute_initializer_result.cpp
@@ -31,6 +30,7 @@ vespa_add_library(searchcore_attribute STATIC
     document_field_extractor.cpp
     document_field_populator.cpp
     document_field_retriever.cpp
+    exclusive_attribute_read_accessor.cpp
     filter_attribute_manager.cpp
     flushableattribute.cpp
     imported_attributes_context.cpp
diff --git a/searchcore/src/vespa/searchcore/proton/attribute/attribute_executor.cpp b/searchcore/src/vespa/searchcore/proton/attribute/attribute_executor.cpp
deleted file mode 100644
index 4d854bfdca1..00000000000
--- a/searchcore/src/vespa/searchcore/proton/attribute/attribute_executor.cpp
+++ /dev/null
@@ -1,34 +0,0 @@
-// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
-
-#include "attribute_executor.h"
-#include "i_attribute_manager.h"
-#include <vespa/searchlib/attribute/attributevector.h>
-#include <vespa/vespalib/util/isequencedtaskexecutor.h>
-#include <future>
-
-using search::AttributeVector;
-
-namespace proton {
-
-AttributeExecutor::AttributeExecutor(std::shared_ptr<IAttributeManager> mgr,
-                                     std::shared_ptr<AttributeVector> attr)
-    : _mgr(std::move(mgr)),
-      _attr(std::move(attr))
-{
-}
-
-AttributeExecutor::~AttributeExecutor() = default;
-
-void
-AttributeExecutor::run_sync(std::function<void()> task) const
-{
-    vespalib::string name = _attr->getNamePrefix();
-    auto& writer = _mgr->getAttributeFieldWriter();
-    std::promise<void> promise;
-    auto future = promise.get_future();
-    auto id = writer.getExecutorIdFromName(name);
-    writer.execute(id, [&task, promise=std::move(promise)]() mutable { task(); promise.set_value(); });
-    future.wait();
-}
-
-} // namespace proton
diff --git a/searchcore/src/vespa/searchcore/proton/attribute/attribute_executor.h b/searchcore/src/vespa/searchcore/proton/attribute/attribute_executor.h
deleted file mode 100644
index 4a13fe1d886..00000000000
--- a/searchcore/src/vespa/searchcore/proton/attribute/attribute_executor.h
+++ /dev/null
@@ -1,32 +0,0 @@
-// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
-
-#pragma once
-
-#include <vespa/vespalib/stllike/string.h>
-#include <functional>
-#include <memory>
-
-namespace search { class AttributeVector; }
-
-namespace proton {
-
-struct IAttributeManager;
-
-/*
- * Class for executing task in attribute vector write thread.
- */
-class AttributeExecutor
-{
-private:
-    std::shared_ptr<IAttributeManager>           _mgr;
-    std::shared_ptr<search::AttributeVector>     _attr;
-
-public:
-    AttributeExecutor(std::shared_ptr<IAttributeManager> mgr,
-                      std::shared_ptr<search::AttributeVector> attr);
-    ~AttributeExecutor();
-    void run_sync(std::function<void()> task) const;
-    const search::AttributeVector& get_attr() const noexcept { return *_attr; }
-};
-
-} // namespace proton
diff --git a/searchcore/src/vespa/searchcore/proton/attribute/attribute_manager_explorer.cpp b/searchcore/src/vespa/searchcore/proton/attribute/attribute_manager_explorer.cpp
index 1ea02c729ff..b7d6cf9e87a 100644
--- a/searchcore/src/vespa/searchcore/proton/attribute/attribute_manager_explorer.cpp
+++ b/searchcore/src/vespa/searchcore/proton/attribute/attribute_manager_explorer.cpp
@@ -1,11 +1,9 @@
 // Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
 
 #include "attribute_manager_explorer.h"
-#include "attribute_executor.h"
 #include "attribute_vector_explorer.h"
 #include <vespa/searchlib/attribute/attributevector.h>
 
-using search::AttributeVector;
 using vespalib::slime::Inserter;
 
 namespace proton {
@@ -27,7 +25,8 @@ AttributeManagerExplorer::get_state(const Inserter &inserter, bool full) const
 std::vector<vespalib::string>
 AttributeManagerExplorer::get_children_names() const
 {
-    auto& attributes = _mgr->getWritableAttributes();
+    std::vector<search::AttributeGuard> attributes;
+    _mgr->getAttributeListAll(attributes);
     std::vector<vespalib::string> names;
     for (const auto &attr : attributes) {
         names.push_back(attr->getName());
@@ -38,13 +37,11 @@ AttributeManagerExplorer::get_children_names() const
 std::unique_ptr<vespalib::StateExplorer>
 AttributeManagerExplorer::get_child(vespalib::stringref name) const
 {
-    auto guard = _mgr->getAttribute(name);
-    auto attr = guard ? guard->getSP() : std::shared_ptr<AttributeVector>();
-    if (attr && _mgr->getWritableAttribute(name) != nullptr) {
-        auto executor = std::make_unique<AttributeExecutor>(_mgr, std::move(attr));
-        return std::make_unique<AttributeVectorExplorer>(std::move(executor));
+    auto attr = _mgr->getExclusiveReadAccessor(name);
+    if (attr.get() != nullptr) {
+        return std::make_unique<AttributeVectorExplorer>(std::move(attr));
     }
-    return {};
+    return std::unique_ptr<vespalib::StateExplorer>();
 }
 
 } // namespace proton
diff --git a/searchcore/src/vespa/searchcore/proton/attribute/attribute_vector_explorer.cpp b/searchcore/src/vespa/searchcore/proton/attribute/attribute_vector_explorer.cpp
index 2deabeda797..c153f873480 100644
--- a/searchcore/src/vespa/searchcore/proton/attribute/attribute_vector_explorer.cpp
+++ b/searchcore/src/vespa/searchcore/proton/attribute/attribute_vector_explorer.cpp
@@ -1,7 +1,6 @@
 // Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
 
 #include "attribute_vector_explorer.h"
-#include "attribute_executor.h"
 #include <vespa/searchlib/attribute/i_enum_store.h>
 #include <vespa/searchlib/attribute/i_enum_store_dictionary.h>
 #include <vespa/searchlib/attribute/multi_value_mapping.h>
@@ -18,7 +17,6 @@ using search::IEnumStore;
 using vespalib::AddressSpace;
 using vespalib::MemoryUsage;
 using search::attribute::MultiValueMappingBase;
-using search::attribute::IAttributeVector;
 using search::attribute::IPostingListAttributeBase;
 using namespace vespalib::slime;
 
@@ -118,21 +116,16 @@ convertPostingBaseToSlime(const IPostingListAttributeBase &postingBase, Cursor &
 
 }
 
-AttributeVectorExplorer::AttributeVectorExplorer(std::unique_ptr<AttributeExecutor> executor)
-    : _executor(std::move(executor))
+AttributeVectorExplorer::AttributeVectorExplorer(ExclusiveAttributeReadAccessor::UP attribute)
+    : _attribute(std::move(attribute))
 {
 }
 
 void
 AttributeVectorExplorer::get_state(const vespalib::slime::Inserter &inserter, bool full) const
 {
-    auto& attr = _executor->get_attr();
-    _executor->run_sync([this, &attr, &inserter, full] { get_state_helper(attr, inserter, full); });
-}
-
-void
-AttributeVectorExplorer::get_state_helper(const AttributeVector& attr, const vespalib::slime::Inserter &inserter, bool full) const
-{
+    ExclusiveAttributeReadAccessor::Guard::UP readGuard = _attribute->takeGuard();
+    const AttributeVector &attr = readGuard->get();
     const Status &status = attr.getStatus();
     Cursor &object = inserter.insertObject();
     if (full) {
diff --git a/searchcore/src/vespa/searchcore/proton/attribute/attribute_vector_explorer.h b/searchcore/src/vespa/searchcore/proton/attribute/attribute_vector_explorer.h
index f7bcc98d321..204a81ed629 100644
--- a/searchcore/src/vespa/searchcore/proton/attribute/attribute_vector_explorer.h
+++ b/searchcore/src/vespa/searchcore/proton/attribute/attribute_vector_explorer.h
@@ -2,25 +2,21 @@
 
 #pragma once
 
+#include "exclusive_attribute_read_accessor.h"
 #include <vespa/vespalib/net/http/state_explorer.h>
 
-namespace search { class AttributeVector; }
-
 namespace proton {
 
-class AttributeExecutor;
-
 /**
  * Class used to explore the state of an attribute vector.
  */
 class AttributeVectorExplorer : public vespalib::StateExplorer
 {
 private:
-    std::unique_ptr<const AttributeExecutor> _executor;
+    ExclusiveAttributeReadAccessor::UP _attribute;
 
-    void get_state_helper(const search::AttributeVector& attr, const vespalib::slime::Inserter &inserter, bool full) const;
 public:
-    AttributeVectorExplorer(std::unique_ptr<AttributeExecutor> executor);
+    AttributeVectorExplorer(ExclusiveAttributeReadAccessor::UP attribute);
 
     // Implements vespalib::StateExplorer
     void get_state(const vespalib::slime::Inserter &inserter, bool full) const override;
diff --git a/searchcore/src/vespa/searchcore/proton/attribute/attributemanager.cpp b/searchcore/src/vespa/searchcore/proton/attribute/attributemanager.cpp
index ee04f17d378..161a4294908 100644
--- a/searchcore/src/vespa/searchcore/proton/attribute/attributemanager.cpp
+++ b/searchcore/src/vespa/searchcore/proton/attribute/attributemanager.cpp
@@ -638,6 +638,16 @@ AttributeManager::asyncForAttribute(const vespalib::string &name, std::unique_pt
                                   [attr=std::move(attrsp), func=std::move(func)]() { (*func)(*attr); });
 }
 
+ExclusiveAttributeReadAccessor::UP
+AttributeManager::getExclusiveReadAccessor(const vespalib::string &name) const
+{
+    AttributeVector::SP attribute = findAttribute(name);
+    if (attribute) {
+        return std::make_unique<ExclusiveAttributeReadAccessor>(attribute, _attributeFieldWriter);
+    }
+    return {};
+}
+
 void
 AttributeManager::setImportedAttributes(std::unique_ptr<ImportedAttributesRepo> attributes)
 {
diff --git a/searchcore/src/vespa/searchcore/proton/attribute/attributemanager.h b/searchcore/src/vespa/searchcore/proton/attribute/attributemanager.h
index d6d0964f97e..c924c1c5b20 100644
--- a/searchcore/src/vespa/searchcore/proton/attribute/attributemanager.h
+++ b/searchcore/src/vespa/searchcore/proton/attribute/attributemanager.h
@@ -182,6 +182,8 @@ public:
     void asyncForEachAttribute(std::shared_ptr<IAttributeFunctor> func, OnDone onDone) const override;
     void asyncForAttribute(const vespalib::string &name, std::unique_ptr<IAttributeFunctor> func) const override;
 
+    ExclusiveAttributeReadAccessor::UP getExclusiveReadAccessor(const vespalib::string &name) const override;
+
     void setImportedAttributes(std::unique_ptr<ImportedAttributesRepo> attributes) override;
 
     const ImportedAttributesRepo *getImportedAttributes() const override { return _importedAttributes.get(); }
diff --git a/searchcore/src/vespa/searchcore/proton/attribute/exclusive_attribute_read_accessor.cpp b/searchcore/src/vespa/searchcore/proton/attribute/exclusive_attribute_read_accessor.cpp
new file mode 100644
index 00000000000..ed72418ced4
--- /dev/null
+++ b/searchcore/src/vespa/searchcore/proton/attribute/exclusive_attribute_read_accessor.cpp
@@ -0,0 +1,60 @@
+// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+
+#include "exclusive_attribute_read_accessor.h"
+#include <vespa/vespalib/util/gate.h>
+#include <vespa/searchlib/attribute/attributevector.h>
+#include <vespa/vespalib/util/isequencedtaskexecutor.h>
+
+namespace proton {
+
+using search::AttributeVector;
+using vespalib::ISequencedTaskExecutor;
+using vespalib::Executor;
+using vespalib::Gate;
+
+using GateSP = std::shared_ptr<Gate>;
+
+ExclusiveAttributeReadAccessor::Guard::Guard(const AttributeVector &attribute,
+                                             const GateSP &exitGate)
+    : _attribute(attribute),
+      _exitGate(exitGate)
+{
+}
+
+ExclusiveAttributeReadAccessor::Guard::~Guard()
+{
+    _exitGate->countDown();
+}
+
+ExclusiveAttributeReadAccessor::
+ExclusiveAttributeReadAccessor(const AttributeVector::SP &attribute,
+                               ISequencedTaskExecutor &attributeFieldWriter)
+    : _attribute(attribute),
+      _attributeFieldWriter(attributeFieldWriter)
+{
+}
+
+namespace {
+
+void
+attributeWriteBlockingTask(AttributeVector::SP attribute, GateSP entranceGate, GateSP exitGate)
+{
+    attribute->commit(true);
+    entranceGate->countDown();
+    exitGate->await();
+}
+
+}
+
+ExclusiveAttributeReadAccessor::Guard::UP
+ExclusiveAttributeReadAccessor::takeGuard()
+{
+    GateSP entranceGate = std::make_shared<Gate>();
+    GateSP exitGate = std::make_shared<Gate>();
+    _attributeFieldWriter.execute(_attributeFieldWriter.getExecutorIdFromName(_attribute->getNamePrefix()),
+                                  [this, entranceGate, exitGate]() { attributeWriteBlockingTask(_attribute, entranceGate, exitGate); });
+    entranceGate->await();
+    return std::make_unique<Guard>(*_attribute, exitGate);
+}
+
+} // namespace proton
diff --git a/searchcore/src/vespa/searchcore/proton/attribute/exclusive_attribute_read_accessor.h b/searchcore/src/vespa/searchcore/proton/attribute/exclusive_attribute_read_accessor.h
new file mode 100644
index 00000000000..aa756764b1a
--- /dev/null
+++ b/searchcore/src/vespa/searchcore/proton/attribute/exclusive_attribute_read_accessor.h
@@ -0,0 +1,53 @@
+// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+
+#pragma once
+
+#include <memory>
+
+namespace search {
+    class AttributeVector;
+}
+namespace vespalib {
+    class Gate;
+    class ISequencedTaskExecutor;
+}
+
+namespace proton {
+
+/**
+ * Class that provides exclusive read access to an attribute vector
+ * while the write thread for that attribute is blocked.
+ *
+ * The attribute write thread is blocked while a guard is held.
+ */
+class ExclusiveAttributeReadAccessor
+{
+public:
+    class Guard
+    {
+    private:
+        const search::AttributeVector &_attribute;
+        std::shared_ptr<vespalib::Gate> _exitGate;
+
+    public:
+        using UP = std::unique_ptr<Guard>;
+        Guard(const search::AttributeVector &attribute,
+              const std::shared_ptr<vespalib::Gate> &exitGate);
+        ~Guard();
+        const search::AttributeVector &get() const { return _attribute; }
+    };
+
+private:
+    using AttributeVectorSP = std::shared_ptr<search::AttributeVector>;
+    AttributeVectorSP _attribute;
+    vespalib::ISequencedTaskExecutor &_attributeFieldWriter;
+
+public:
+    using UP = std::unique_ptr<ExclusiveAttributeReadAccessor>;
+
+    ExclusiveAttributeReadAccessor(const AttributeVectorSP &attribute,
+                                   vespalib::ISequencedTaskExecutor &attributeFieldWriter);
+    Guard::UP takeGuard();
+};
+
+} // namespace proton
diff --git a/searchcore/src/vespa/searchcore/proton/attribute/filter_attribute_manager.cpp b/searchcore/src/vespa/searchcore/proton/attribute/filter_attribute_manager.cpp
index 6329c633727..6f6cd01b4a4 100644
--- a/searchcore/src/vespa/searchcore/proton/attribute/filter_attribute_manager.cpp
+++ b/searchcore/src/vespa/searchcore/proton/attribute/filter_attribute_manager.cpp
@@ -232,6 +232,12 @@ FilterAttributeManager::asyncForAttribute(const vespalib::string &name, std::uni
 
 }
 
+ExclusiveAttributeReadAccessor::UP
+FilterAttributeManager::getExclusiveReadAccessor(const vespalib::string &name) const
+{
+    return (acceptAttribute(name)) ? _mgr->getExclusiveReadAccessor(name) : ExclusiveAttributeReadAccessor::UP();
+}
+
 void
 FilterAttributeManager::setImportedAttributes(std::unique_ptr<ImportedAttributesRepo>)
 {
diff --git a/searchcore/src/vespa/searchcore/proton/attribute/filter_attribute_manager.h b/searchcore/src/vespa/searchcore/proton/attribute/filter_attribute_manager.h
index 6d5ff682ca1..dff18290330 100644
--- a/searchcore/src/vespa/searchcore/proton/attribute/filter_attribute_manager.h
+++ b/searchcore/src/vespa/searchcore/proton/attribute/filter_attribute_manager.h
@@ -52,6 +52,7 @@ public:
     const std::vector<search::AttributeVector *> & getWritableAttributes() const override;
     void asyncForEachAttribute(std::shared_ptr<IConstAttributeFunctor> func) const override;
     void asyncForEachAttribute(std::shared_ptr<IAttributeFunctor> func, OnDone onDone) const override;
+    ExclusiveAttributeReadAccessor::UP getExclusiveReadAccessor(const vespalib::string &name) const override;
     void setImportedAttributes(std::unique_ptr<ImportedAttributesRepo> attributes) override;
     const ImportedAttributesRepo *getImportedAttributes() const override;
     std::shared_ptr<search::attribute::ReadableAttributeVector> readable_attribute_vector(const string& name) const override;
diff --git a/searchcore/src/vespa/searchcore/proton/attribute/i_attribute_manager.h b/searchcore/src/vespa/searchcore/proton/attribute/i_attribute_manager.h
index 5e60e950cc4..437e7bd0208 100644
--- a/searchcore/src/vespa/searchcore/proton/attribute/i_attribute_manager.h
+++ b/searchcore/src/vespa/searchcore/proton/attribute/i_attribute_manager.h
@@ -2,6 +2,7 @@
 
 #pragma once
 
+#include "exclusive_attribute_read_accessor.h"
 #include "i_attribute_factory.h"
 #include <vespa/searchcommon/attribute/i_attribute_functor.h>
 #include <vespa/searchcore/proton/common/i_transient_resource_usage_provider.h>
@@ -101,6 +102,8 @@ struct IAttributeManager : public search::IAttributeManager
     virtual void asyncForEachAttribute(std::shared_ptr<IConstAttributeFunctor> func) const = 0;
     virtual void asyncForEachAttribute(std::shared_ptr<IAttributeFunctor> func, OnDone onDone) const = 0;
 
+    virtual ExclusiveAttributeReadAccessor::UP getExclusiveReadAccessor(const vespalib::string &name) const = 0;
+
     virtual void setImportedAttributes(std::unique_ptr<ImportedAttributesRepo> attributes) = 0;
 
     virtual const ImportedAttributesRepo *getImportedAttributes() const = 0;
diff --git a/searchcore/src/vespa/searchcore/proton/test/mock_attribute_manager.h b/searchcore/src/vespa/searchcore/proton/test/mock_attribute_manager.h
index babecb6a77d..f85baa8c0ac 100644
--- a/searchcore/src/vespa/searchcore/proton/test/mock_attribute_manager.h
+++ b/searchcore/src/vespa/searchcore/proton/test/mock_attribute_manager.h
@@ -91,6 +91,9 @@ public:
     void asyncForEachAttribute(std::shared_ptr<IConstAttributeFunctor>) const override { }
     void asyncForEachAttribute(std::shared_ptr<IAttributeFunctor>, OnDone) const override { }
 
+    ExclusiveAttributeReadAccessor::UP getExclusiveReadAccessor(const vespalib::string &) const override {
+        return ExclusiveAttributeReadAccessor::UP();
+    }
     void setImportedAttributes(std::unique_ptr<ImportedAttributesRepo> importedAttributes) override {
         _importedAttributes = std::move(importedAttributes);
     }