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Merged
merged 2 commits into from
Sep 23, 2025
Merged

Defer metrics aggregator classloading to save startup time #9590

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cb4b55d
Revert "Lazily obtain feature discovery when starting client metrics …
amarziali Sep 23, 2025
7352724
Defer metrics aggregator classloading to save startup time
amarziali Sep 23, 2025
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2 changes: 1 addition & 1 deletion ...nt/agent-bootstrap/src/main/java/datadog/trace/bootstrap/benchmark/StaticEventLogger.java
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Original file line number Diff line number Diff line change
Expand Up @@ -97,7 +97,7 @@ private static String getAgentVersion() {
for (int c = reader.read(); c != -1; c = reader.read()) {
sb.append((char) c);
}
} catch (IOException e) {
} catch (Throwable ignored) {
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I don't know why but I had some NPE time by time on my local build. I widen this to Throwable. While is not related to this PR, it's a good thing to do

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NPE likely means the dd-java-agent.version file did not end up in the jar being tested, so it wasn't found

This could point to an issue when doing incremental builds - but proactively widening the catch here makes sense

// swallow exception
return null;
}
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30 changes: 12 additions & 18 deletions ...-core/src/jmh/java/datadog/trace/common/metrics/ConflatingMetricsAggregatorBenchmark.java
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Expand Up @@ -4,7 +4,6 @@
import static java.util.concurrent.TimeUnit.SECONDS;

import datadog.communication.ddagent.DDAgentFeaturesDiscovery;
import datadog.communication.ddagent.SharedCommunicationObjects;
import datadog.communication.monitor.Monitoring;
import datadog.trace.api.WellKnownTags;
import datadog.trace.core.CoreSpan;
Expand Down Expand Up @@ -33,25 +32,20 @@
@OutputTimeUnit(MICROSECONDS)
@Fork(value = 1)
public class ConflatingMetricsAggregatorBenchmark {
private final SharedCommunicationObjects sco = new SharedCommunicationObjects();
private final ConflatingMetricsAggregator aggregator;
private final DDAgentFeaturesDiscovery featuresDiscovery =
new FixedAgentFeaturesDiscovery(
Collections.singleton("peer.hostname"), Collections.emptySet());
private final ConflatingMetricsAggregator aggregator =
new ConflatingMetricsAggregator(
new WellKnownTags("", "", "", "", "", ""),
Collections.emptySet(),
featuresDiscovery,
HealthMetrics.NO_OP,
new NullSink(),
2048,
2048);
private final List<CoreSpan<?>> spans = generateTrace(64);

public ConflatingMetricsAggregatorBenchmark() {
sco.setFeaturesDiscovery(
new FixedAgentFeaturesDiscovery(
Collections.singleton("peer.hostname"), Collections.emptySet()));
aggregator =
new ConflatingMetricsAggregator(
new WellKnownTags("", "", "", "", "", ""),
Collections.emptySet(),
sco,
HealthMetrics.NO_OP,
new NullSink(),
2048,
2048);
}

static List<CoreSpan<?>> generateTrace(int len) {
final List<CoreSpan<?>> trace = new ArrayList<>();
for (int i = 0; i < len; i++) {
Expand Down
54 changes: 23 additions & 31 deletions dd-trace-core/src/main/java/datadog/trace/common/metrics/ConflatingMetricsAggregator.java
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Expand Up @@ -98,8 +98,7 @@ public final class ConflatingMetricsAggregator implements MetricsAggregator, Eve
private final Aggregator aggregator;
private final long reportingInterval;
private final TimeUnit reportingIntervalTimeUnit;
private final SharedCommunicationObjects sharedCommunicationObjects;
private volatile DDAgentFeaturesDiscovery features;
private final DDAgentFeaturesDiscovery features;
private final HealthMetrics healthMetrics;

private volatile AgentTaskScheduler.Scheduled<?> cancellation;
Expand All @@ -111,7 +110,7 @@ public ConflatingMetricsAggregator(
this(
config.getWellKnownTags(),
config.getMetricsIgnoredResources(),
sharedCommunicationObjects,
sharedCommunicationObjects.featuresDiscovery(config),
healthMetrics,
new OkHttpSink(
sharedCommunicationObjects.okHttpClient,
Expand All @@ -127,15 +126,15 @@ public ConflatingMetricsAggregator(
ConflatingMetricsAggregator(
WellKnownTags wellKnownTags,
Set<String> ignoredResources,
SharedCommunicationObjects sharedCommunicationObjects,
DDAgentFeaturesDiscovery features,
HealthMetrics healthMetric,
Sink sink,
int maxAggregates,
int queueSize) {
this(
wellKnownTags,
ignoredResources,
sharedCommunicationObjects,
features,
healthMetric,
sink,
maxAggregates,
Expand All @@ -147,7 +146,7 @@ public ConflatingMetricsAggregator(
ConflatingMetricsAggregator(
WellKnownTags wellKnownTags,
Set<String> ignoredResources,
SharedCommunicationObjects sharedCommunicationObjects,
DDAgentFeaturesDiscovery features,
HealthMetrics healthMetric,
Sink sink,
int maxAggregates,
Expand All @@ -156,7 +155,7 @@ public ConflatingMetricsAggregator(
TimeUnit timeUnit) {
this(
ignoredResources,
sharedCommunicationObjects,
features,
healthMetric,
sink,
new SerializingMetricWriter(wellKnownTags, sink),
Expand All @@ -168,7 +167,7 @@ public ConflatingMetricsAggregator(

ConflatingMetricsAggregator(
Set<String> ignoredResources,
SharedCommunicationObjects sharedCommunicationObjects,
DDAgentFeaturesDiscovery features,
HealthMetrics healthMetric,
Sink sink,
MetricWriter metricWriter,
Expand All @@ -181,7 +180,7 @@ public ConflatingMetricsAggregator(
this.batchPool = new SpmcArrayQueue<>(maxAggregates);
this.pending = new NonBlockingHashMap<>(maxAggregates * 4 / 3);
this.keys = new NonBlockingHashMap<>();
this.sharedCommunicationObjects = sharedCommunicationObjects;
this.features = features;
this.healthMetrics = healthMetric;
this.sink = sink;
this.aggregator =
Expand All @@ -199,18 +198,6 @@ public ConflatingMetricsAggregator(
this.reportingIntervalTimeUnit = timeUnit;
}

private DDAgentFeaturesDiscovery featuresDiscovery() {
DDAgentFeaturesDiscovery ret = features;
if (ret != null) {
return ret;
}
// no need to synchronise here since it's already done in sharedCommunicationObject.
// At worst, we'll assign multiple time the variable but it will be the same object
ret = sharedCommunicationObjects.featuresDiscovery(Config.get());
features = ret;
return ret;
}

@Override
public void start() {
sink.register(this);
Expand All @@ -226,6 +213,13 @@ public void start() {
log.debug("started metrics aggregator");
}

private boolean isMetricsEnabled() {
if (features.getMetricsEndpoint() == null) {
features.discoverIfOutdated();
}
return features.supportsMetrics();
}

@Override
public boolean report() {
boolean published;
Expand All @@ -242,7 +236,8 @@ public boolean report() {

@Override
public Future<Boolean> forceReport() {
if (!featuresDiscovery().supportsMetrics()) {
// Ensure the feature is enabled
if (!isMetricsEnabled()) {
return CompletableFuture.completedFuture(false);
}
// Wait for the thread to start
Expand Down Expand Up @@ -278,7 +273,6 @@ public Future<Boolean> forceReport() {
public boolean publish(List<? extends CoreSpan<?>> trace) {
boolean forceKeep = false;
int counted = 0;
final DDAgentFeaturesDiscovery features = featuresDiscovery();
if (features.supportsMetrics()) {
for (CoreSpan<?> span : trace) {
boolean isTopLevel = span.isTopLevel();
Expand All @@ -289,7 +283,7 @@ public boolean publish(List<? extends CoreSpan<?>> trace) {
break;
}
counted++;
forceKeep |= publish(span, isTopLevel, features);
forceKeep |= publish(span, isTopLevel);
}
}
healthMetrics.onClientStatTraceComputed(
Expand All @@ -311,7 +305,7 @@ private boolean spanKindEligible(CoreSpan<?> span) {
return spanKind != null && ELIGIBLE_SPAN_KINDS_FOR_METRICS.contains(spanKind.toString());
}

private boolean publish(CoreSpan<?> span, boolean isTopLevel, DDAgentFeaturesDiscovery features) {
private boolean publish(CoreSpan<?> span, boolean isTopLevel) {
final CharSequence spanKind = span.getTag(SPAN_KIND, "");
MetricKey newKey =
new MetricKey(
Expand All @@ -324,7 +318,7 @@ private boolean publish(CoreSpan<?> span, boolean isTopLevel, DDAgentFeaturesDis
span.getParentId() == 0,
SPAN_KINDS.computeIfAbsent(
spanKind, UTF8BytesString::create), // save repeated utf8 conversions
getPeerTags(span, spanKind.toString(), features));
getPeerTags(span, spanKind.toString()));
boolean isNewKey = false;
MetricKey key = keys.putIfAbsent(newKey, newKey);
if (null == key) {
Expand Down Expand Up @@ -359,8 +353,7 @@ private boolean publish(CoreSpan<?> span, boolean isTopLevel, DDAgentFeaturesDis
return isNewKey || span.getError() > 0;
}

private List<UTF8BytesString> getPeerTags(
CoreSpan<?> span, String spanKind, DDAgentFeaturesDiscovery features) {
private List<UTF8BytesString> getPeerTags(CoreSpan<?> span, String spanKind) {
if (ELIGIBLE_SPAN_KINDS_FOR_PEER_AGGREGATION.contains(spanKind)) {
List<UTF8BytesString> peerTags = new ArrayList<>();
for (String peerTag : features.peerTags()) {
Expand Down Expand Up @@ -424,7 +417,8 @@ public void onEvent(EventType eventType, String message) {
switch (eventType) {
case DOWNGRADED:
log.debug("Agent downgrade was detected");
AgentTaskScheduler.get().execute(this::disable);
disable();
healthMetrics.onClientStatDowngraded();
break;
case BAD_PAYLOAD:
log.debug("bad metrics payload sent to trace agent: {}", message);
Expand All @@ -440,11 +434,9 @@ public void onEvent(EventType eventType, String message) {
}

private void disable() {
final DDAgentFeaturesDiscovery features = featuresDiscovery();
features.discover();
if (!features.supportsMetrics()) {
log.debug("Disabling metric reporting because an agent downgrade was detected");
healthMetrics.onClientStatDowngraded();
this.pending.clear();
this.batchPool.clear();
this.inbox.clear();
Expand Down
2 changes: 1 addition & 1 deletion dd-trace-core/src/main/java/datadog/trace/common/metrics/NoOpMetricsAggregator.java
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Expand Up @@ -9,7 +9,7 @@

public final class NoOpMetricsAggregator implements MetricsAggregator {

static final NoOpMetricsAggregator INSTANCE = new NoOpMetricsAggregator();
public static final NoOpMetricsAggregator INSTANCE = new NoOpMetricsAggregator();

@Override
public void start() {}
Expand Down
27 changes: 19 additions & 8 deletions dd-trace-core/src/main/java/datadog/trace/core/CoreTracer.java
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Expand Up @@ -72,6 +72,7 @@
import datadog.trace.civisibility.interceptor.CiVisibilityTraceInterceptor;
import datadog.trace.common.GitMetadataTraceInterceptor;
import datadog.trace.common.metrics.MetricsAggregator;
import datadog.trace.common.metrics.NoOpMetricsAggregator;
import datadog.trace.common.sampling.Sampler;
import datadog.trace.common.sampling.SingleSpanSampler;
import datadog.trace.common.sampling.SpanSamplingRules;
Expand Down Expand Up @@ -182,7 +183,7 @@ public static CoreTracerBuilder builder() {
/** Scope manager is in charge of managing the scopes from which spans are created */
final ContinuableScopeManager scopeManager;

final MetricsAggregator metricsAggregator;
volatile MetricsAggregator metricsAggregator;

/** Initial static configuration associated with the tracer. */
final Config initialConfig;
Expand Down Expand Up @@ -783,16 +784,26 @@ private CoreTracer(
pendingTraceBuffer.start();

sharedCommunicationObjects.whenReady(this.writer::start);

metricsAggregator =
createMetricsAggregator(config, sharedCommunicationObjects, this.healthMetrics);
// Schedule the metrics aggregator to begin reporting after a random delay of 1 to 10 seconds
// (using milliseconds granularity.) This avoids a fleet of traced applications starting at the
// same time from sending metrics in sync.
// temporary assign a no-op instance. The final one will be resolved when the discovery will be
// allowed
metricsAggregator = NoOpMetricsAggregator.INSTANCE;
final SharedCommunicationObjects sco = sharedCommunicationObjects;
// asynchronously create the aggregator to avoid triggering expensive classloading during the
// tracer initialisation.
sharedCommunicationObjects.whenReady(
() ->
AgentTaskScheduler.get()
.scheduleWithJitter(MetricsAggregator::start, metricsAggregator, 1, SECONDS));
.execute(
() -> {
metricsAggregator = createMetricsAggregator(config, sco, this.healthMetrics);
// Schedule the metrics aggregator to begin reporting after a random delay of
// 1 to 10 seconds (using milliseconds granularity.)
// This avoids a fleet of traced applications starting at the same time from
// sending metrics in sync.
AgentTaskScheduler.get()
.scheduleWithJitter(
MetricsAggregator::start, metricsAggregator, 1, SECONDS);
}));

if (dataStreamsMonitoring == null) {
this.dataStreamsMonitoring =
Expand Down
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