Make it lazy and safe.

3 files changed, 40 insertions, 38 deletions

diff --git a/searchlib/src/tests/engine/searchapi/searchapi_test.cpp b/searchlib/src/tests/engine/searchapi/searchapi_test.cpp
index 28c90dd18ca..ed103bf501c 100644
--- a/searchlib/src/tests/engine/searchapi/searchapi_test.cpp
+++ b/searchlib/src/tests/engine/searchapi/searchapi_test.cpp
@@ -228,21 +228,18 @@ TEST("convertFromReply") {
     }
 }
 
-void verify(vespalib::stringref expected, const vespalib::Slime * slime) {
+void verify(vespalib::stringref expected, const vespalib::Slime & slime) {
     vespalib::Slime expectedSlime;
     vespalib::slime::JsonFormat::decode(expected, expectedSlime);
-    if (slime) {
-        EXPECT_EQUAL(expectedSlime, *slime);
-    } else {
-        EXPECT_TRUE(expected.empty());
-    }
+    EXPECT_EQUAL(expectedSlime, slime);
 }
 
 TEST("verify trace") {
     RelativeTime clock(std::make_unique<CountingClock>(fastos::TimeStamp::fromSec(1500000000), 1700000L));
     Trace t(clock);
-    verify("", t.getSlime());
+    EXPECT_FALSE(t.hasTrace());
     t.start(0);
+    EXPECT_TRUE(t.hasTrace());
     t.createCursor("tag_a");
     verify("{"
            "    start_time_utc: '2017-07-14 02:40:00.000 UTC',"
diff --git a/searchlib/src/vespa/searchlib/engine/trace.cpp b/searchlib/src/vespa/searchlib/engine/trace.cpp
index c9e3a39daa4..f9564846104 100644
--- a/searchlib/src/vespa/searchlib/engine/trace.cpp
+++ b/searchlib/src/vespa/searchlib/engine/trace.cpp
@@ -11,22 +11,14 @@ RelativeTime::RelativeTime(std::unique_ptr<Clock> clock)
 {}
 
 void
-Trace::constructObject() {
+Trace::constructObject() const {
     _trace = std::make_unique<vespalib::Slime>();
     _root = & _trace->setObject();
 }
 
 void
-Trace::constructTraces() {
-    _traces = &_root->setArray("traces");
-}
-
-void
-Trace::lazyConstruct(uint32_t level) {
-    if (shouldTrace(level) && !_trace) {
-        constructObject();
-        constructTraces();
-    }
+Trace::constructTraces() const {
+    _traces = & root().setArray("traces");
 }
 
 Trace::Trace(const RelativeTime & relativeTime, uint32_t level)
@@ -40,10 +32,8 @@ Trace::Trace(const RelativeTime & relativeTime, uint32_t level)
 
 void
 Trace::start(int level) {
-    if (shouldTrace(level) && !_trace) {
-        constructObject();
-        _root->setString("start_time_utc", _relativeTime.timeOfDawn().toString());
-        constructTraces();
+    if (shouldTrace(level) && !hasTrace()) {
+        root().setString("start_time_utc", _relativeTime.timeOfDawn().toString());
     }
 }
 
@@ -51,8 +41,7 @@ Trace::~Trace() = default;
 
 Trace::Cursor &
 Trace::createCursor(vespalib::stringref name) {
-    lazyConstruct(_level);
-    Cursor & trace = _traces->addObject();
+    Cursor & trace = traces().addObject();
     addTimeStamp(trace);
     trace.setString("tag", name);
     return trace;
@@ -60,7 +49,6 @@ Trace::createCursor(vespalib::stringref name) {
 
 Trace::Cursor *
 Trace::maybeCreateCursor(uint32_t level, vespalib::stringref name) {
-    lazyConstruct(level);
     return shouldTrace(level) ? & createCursor(name) : nullptr;
 }
 
@@ -68,8 +56,7 @@ void
 Trace::addEvent(uint32_t level, vespalib::stringref event) {
     if (!shouldTrace(level)) { return; }
 
-    lazyConstruct(level);
-    Cursor & trace = _traces->addObject();
+    Cursor & trace = traces().addObject();
     addTimeStamp(trace);
     trace.setString("event", event);
 }
@@ -80,14 +67,14 @@ Trace::addTimeStamp(Cursor & trace) {
 }
 
 void Trace::done() {
-    if (!_root) { return; }
+    if (!hasTrace()) { return; }
 
-    _root->setDouble("duration_ms", _relativeTime.timeSinceDawn()/1000000.0);
+    root().setDouble("duration_ms", _relativeTime.timeSinceDawn()/1000000.0);
 }
 
 vespalib::string
 Trace::toString() const {
-    return _trace ? _trace->toString() : "";
+    return hasTrace() ? slime().toString() : "";
 }
 
 }
diff --git a/searchlib/src/vespa/searchlib/engine/trace.h b/searchlib/src/vespa/searchlib/engine/trace.h
index 78832733f71..e5fea4f2b7f 100644
--- a/searchlib/src/vespa/searchlib/engine/trace.h
+++ b/searchlib/src/vespa/searchlib/engine/trace.h
@@ -82,20 +82,38 @@ public:
     void done();
 
     vespalib::string toString() const;
-    Cursor * getRoot() const { return _root; }
-    vespalib::Slime * getSlime() const { return _trace.get(); }
+    bool hasTrace() const { return static_cast<bool>(_trace); }
+    Cursor & getRoot() const { return root(); }
+    vespalib::Slime & getSlime() const { return slime(); }
     bool shouldTrace(uint32_t level) const { return level <= _level; }
     uint32_t getLevel() const { return _level; }
     Trace & setLevel(uint32_t level) { _level = level; return *this; }
     const RelativeTime & getRelativeTime() const { return _relativeTime; }
 private:
-    void constructObject();
-    void constructTraces();
-    void lazyConstruct(uint32_t level);
+    vespalib::Slime & slime() const {
+        if (!hasTrace()) {
+            constructObject();
+        }
+        return *_trace;
+    }
+    Cursor & root() const {
+        if (!hasTrace()) {
+            constructObject();
+        }
+        return *_root;
+    }
+    Cursor & traces() const {
+        if (!_traces) {
+            constructTraces();
+        }
+        return *_traces;
+    }
+    void constructObject() const;
+    void constructTraces() const;
     void addTimeStamp(Cursor & trace);
-    std::unique_ptr<vespalib::Slime> _trace;
-    Cursor              * _root;
-    Cursor              * _traces;
+    mutable std::unique_ptr<vespalib::Slime> _trace;
+    mutable Cursor              * _root;
+    mutable Cursor              * _traces;
     const RelativeTime  & _relativeTime;
     uint32_t              _level;
 };