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Merged
gh-worker-dd-mergequeue-cf854d merged 3 commits into from
Apr 14, 2026
Merged

Optimize scope lifecycle hot path #11079

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94cfb4f
Optimize scope lifecycle by skipping work when listeners empty and pr…
bm1549 Apr 10, 2026
1e13d53
Fix activeSpanLookup benchmark to exercise live scope stack
bm1549 Apr 10, 2026
f21e7d4
Cache isEmpty() results in local variables to avoid redundant volatil…
bm1549 Apr 10, 2026
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78 changes: 78 additions & 0 deletions dd-trace-core/src/jmh/java/datadog/trace/core/ScopeLifecycleBenchmark.java
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Original file line number Diff line number Diff line change
@@ -0,0 +1,78 @@
package datadog.trace.core;

import static java.util.concurrent.TimeUnit.MICROSECONDS;

import datadog.trace.bootstrap.instrumentation.api.AgentScope;
import datadog.trace.bootstrap.instrumentation.api.AgentSpan;
import org.openjdk.jmh.annotations.Benchmark;
import org.openjdk.jmh.annotations.BenchmarkMode;
import org.openjdk.jmh.annotations.Fork;
import org.openjdk.jmh.annotations.Level;
import org.openjdk.jmh.annotations.Measurement;
import org.openjdk.jmh.annotations.Mode;
import org.openjdk.jmh.annotations.OutputTimeUnit;
import org.openjdk.jmh.annotations.Scope;
import org.openjdk.jmh.annotations.Setup;
import org.openjdk.jmh.annotations.State;
import org.openjdk.jmh.annotations.TearDown;
import org.openjdk.jmh.annotations.Threads;
import org.openjdk.jmh.annotations.Warmup;

@State(Scope.Benchmark)
@Warmup(iterations = 3)
@Measurement(iterations = 5)
@BenchmarkMode(Mode.Throughput)
@Threads(8)
@OutputTimeUnit(MICROSECONDS)
@Fork(value = 1)
public class ScopeLifecycleBenchmark {
static final CoreTracer TRACER = CoreTracer.builder().build();

@State(Scope.Thread)
public static class ThreadState {
AgentSpan span;
AgentSpan childSpan;
AgentScope activeScope;

@Setup(Level.Iteration)
public void setup() {
span = TRACER.startSpan("benchmark", "parent");
childSpan = TRACER.startSpan("benchmark", "child");
activeScope = TRACER.activateSpan(span);
}

@TearDown(Level.Iteration)
public void tearDown() {
activeScope.close();
childSpan.finish();
span.finish();
}
}

@Benchmark
public void activateAndClose(ThreadState state) {
AgentScope scope = TRACER.activateSpan(state.span);
scope.close();
}

@Benchmark
public void activateSameSpan(ThreadState state) {
AgentScope outer = TRACER.activateSpan(state.span);
AgentScope inner = TRACER.activateSpan(state.span);
inner.close();
outer.close();
}

@Benchmark
public void nestedActivateAndClose(ThreadState state) {
AgentScope parentScope = TRACER.activateSpan(state.span);
AgentScope childScope = TRACER.activateSpan(state.childSpan);
childScope.close();
parentScope.close();
}

@Benchmark
public AgentSpan activeSpanLookup() {
return TRACER.activeSpan();
}
}
58 changes: 35 additions & 23 deletions dd-trace-core/src/main/java/datadog/trace/core/scopemanager/ContinuableScope.java
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Expand Up @@ -80,19 +80,22 @@ void cleanup(final ScopeStack scopeStack) {
* I would hope this becomes unnecessary.
*/
final void onProperClose() {
for (final ScopeListener listener : scopeManager.scopeListeners) {
try {
listener.afterScopeClosed();
} catch (Exception e) {
ContinuableScopeManager.log.debug("ScopeListener threw exception in close()", e);
if (!scopeManager.scopeListeners.isEmpty()) {
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@dougqh dougqh Apr 10, 2026

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I think this change makes sense. Although in my experience usually the Iterator gets stack allocated by the JIT, so I'm not sure the provided explanation makes sense here.

That said, we'd have to look at an allocation profile to know for certain.

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@bm1549 bm1549 Apr 10, 2026

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Dug into this and the more accurate explanation is

It avoids the iteration dispatch path entirely, whether or not the JIT scalar-replaces the iterator, the isEmpty() check is fewer instructions and method calls than entering and immediately exiting the for-each loop.

for (final ScopeListener listener : scopeManager.scopeListeners) {
try {
listener.afterScopeClosed();
} catch (Exception e) {
ContinuableScopeManager.log.debug("ScopeListener threw exception in close()", e);
}
}
}

for (final ExtendedScopeListener listener : scopeManager.extendedScopeListeners) {
try {
listener.afterScopeClosed();
} catch (Exception e) {
ContinuableScopeManager.log.debug("ScopeListener threw exception in close()", e);
if (!scopeManager.extendedScopeListeners.isEmpty()) {
for (final ExtendedScopeListener listener : scopeManager.extendedScopeListeners) {
try {
listener.afterScopeClosed();
} catch (Exception e) {
ContinuableScopeManager.log.debug("ScopeListener threw exception in close()", e);
}
}
}
}
Expand Down Expand Up @@ -154,6 +157,9 @@ public boolean rollback() {
}

public final void beforeActivated() {
if (scopeState == Stateful.DEFAULT) {
return;
}
AgentSpan span = span();
if (span == null) {
return;
Expand All @@ -167,24 +173,30 @@ public final void beforeActivated() {
}

public final void afterActivated() {
if (scopeManager.scopeListeners.isEmpty() && scopeManager.extendedScopeListeners.isEmpty()) {
return;
}
AgentSpan span = span();
if (span == null) {
return;
}
for (final ScopeListener listener : scopeManager.scopeListeners) {
try {
listener.afterScopeActivated();
} catch (Throwable e) {
ContinuableScopeManager.log.debug("ScopeListener threw exception in afterActivated()", e);
if (!scopeManager.scopeListeners.isEmpty()) {
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for (final ScopeListener listener : scopeManager.scopeListeners) {
try {
listener.afterScopeActivated();
} catch (Throwable e) {
ContinuableScopeManager.log.debug("ScopeListener threw exception in afterActivated()", e);
}
}
}

for (final ExtendedScopeListener listener : scopeManager.extendedScopeListeners) {
try {
listener.afterScopeActivated(span.getTraceId(), span.getSpanId());
} catch (Throwable e) {
ContinuableScopeManager.log.debug(
"ExtendedScopeListener threw exception in afterActivated()", e);
if (!scopeManager.extendedScopeListeners.isEmpty()) {
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for (final ExtendedScopeListener listener : scopeManager.extendedScopeListeners) {
try {
listener.afterScopeActivated(span.getTraceId(), span.getSpanId());
} catch (Throwable e) {
ContinuableScopeManager.log.debug(
"ExtendedScopeListener threw exception in afterActivated()", e);
}
}
}
}
Expand Down
34 changes: 23 additions & 11 deletions dd-trace-core/src/main/java/datadog/trace/core/scopemanager/ContinuableScopeManager.java
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Expand Up @@ -58,6 +58,8 @@ public final class ContinuableScopeManager implements ContextManager {
private final int depthLimit;
final HealthMetrics healthMetrics;
private final ProfilingContextIntegration profilingContextIntegration;
private final boolean profilingEnabled;
private final boolean hasDepthLimit;

/**
* Constructor with NOOP Profiling and HealthMetrics implementations.
Expand All @@ -81,12 +83,15 @@ public ContinuableScopeManager(
final ProfilingContextIntegration profilingContextIntegration,
final HealthMetrics healthMetrics) {
this.depthLimit = depthLimit == 0 ? Integer.MAX_VALUE : depthLimit;
this.hasDepthLimit = this.depthLimit < Integer.MAX_VALUE;
this.strictMode = strictMode;
this.scopeListeners = new CopyOnWriteArrayList<>();
this.extendedScopeListeners = new CopyOnWriteArrayList<>();
this.healthMetrics = healthMetrics;
this.tlsScopeStack = new ScopeStackThreadLocal(profilingContextIntegration);
this.profilingContextIntegration = profilingContextIntegration;
this.profilingEnabled =
!(profilingContextIntegration instanceof ProfilingContextIntegration.NoOp);

ContextManager.register(this);
}
Expand Down Expand Up @@ -135,11 +140,13 @@ private AgentScope activate(
}

// DQH - This check could go before the check above, since depth limit checking is fast
final int currentDepth = scopeStack.depth();
if (depthLimit <= currentDepth) {
healthMetrics.onScopeStackOverflow();
log.debug("Scope depth limit exceeded ({}). Returning NoopScope.", currentDepth);
return noopScope();
if (hasDepthLimit) {
final int currentDepth = scopeStack.depth();
if (depthLimit <= currentDepth) {
healthMetrics.onScopeStackOverflow();
log.debug("Scope depth limit exceeded ({}). Returning NoopScope.", currentDepth);
return noopScope();
}
}

assert span != null;
Expand Down Expand Up @@ -170,11 +177,13 @@ private AgentScope activate(final Context context) {
}

// DQH - This check could go before the check above, since depth limit checking is fast
final int currentDepth = scopeStack.depth();
if (depthLimit <= currentDepth) {
healthMetrics.onScopeStackOverflow();
log.debug("Scope depth limit exceeded ({}). Returning NoopScope.", currentDepth);
return noopScope();
if (hasDepthLimit) {
final int currentDepth = scopeStack.depth();
if (depthLimit <= currentDepth) {
healthMetrics.onScopeStackOverflow();
log.debug("Scope depth limit exceeded ({}). Returning NoopScope.", currentDepth);
return noopScope();
}
}

assert context != null;
Expand Down Expand Up @@ -263,7 +272,7 @@ public AgentScope activateNext(final AgentSpan span) {
ScopeStack scopeStack = scopeStack();

final int currentDepth = scopeStack.depth();
if (depthLimit <= currentDepth) {
if (hasDepthLimit && depthLimit <= currentDepth) {
healthMetrics.onScopeStackOverflow();
log.debug("Scope depth limit exceeded ({}). Returning NoopScope.", currentDepth);
return noopScope();
Expand Down Expand Up @@ -341,6 +350,9 @@ private void addExtendedScopeListener(final ExtendedScopeListener listener) {
}

private Stateful createScopeState(Context context) {
if (!profilingEnabled) {
return Stateful.DEFAULT;
}
// currently this just manages things the profiler has to do per scope, but could be expanded
// to encapsulate other scope lifecycle activities
// FIXME DDSpanContext is always a ProfilerContext anyway...
Expand Down
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