Implement health metrics for client stats

communication/src/main/java/datadog/communication/ddagent/DDAgentFeaturesDiscovery.java

@@ -365,7 +365,7 @@ public boolean supportsDebuggerDiagnostics() {
     return debuggerDiagnosticsEndpoint != null;
   }
 
-  boolean supportsDropping() {
+  public boolean supportsDropping() {
     return supportsDropping;
   }
 

dd-trace-core/src/main/java/datadog/trace/common/metrics/ConflatingMetricsAggregator.java

@@ -23,6 +23,7 @@
 import datadog.trace.common.writer.ddagent.DDAgentApi;
 import datadog.trace.core.CoreSpan;
 import datadog.trace.core.DDTraceCoreInfo;
+import datadog.trace.core.monitor.HealthMetrics;
 import datadog.trace.util.AgentTaskScheduler;
 import java.util.Collections;
 import java.util.List;
@@ -61,15 +62,19 @@ public final class ConflatingMetricsAggregator implements MetricsAggregator, Eve
   private final long reportingInterval;
   private final TimeUnit reportingIntervalTimeUnit;
   private final DDAgentFeaturesDiscovery features;
+  private final HealthMetrics healthMetrics;
 
   private volatile AgentTaskScheduler.Scheduled<?> cancellation;
 
   public ConflatingMetricsAggregator(
-      Config config, SharedCommunicationObjects sharedCommunicationObjects) {
+      Config config,
+      SharedCommunicationObjects sharedCommunicationObjects,
+      HealthMetrics healthMetrics) {
     this(
         config.getWellKnownTags(),
         config.getMetricsIgnoredResources(),
         sharedCommunicationObjects.featuresDiscovery(config),
+        healthMetrics,
         new OkHttpSink(
             sharedCommunicationObjects.okHttpClient,
             sharedCommunicationObjects.agentUrl.toString(),
@@ -85,16 +90,27 @@ public ConflatingMetricsAggregator(
       WellKnownTags wellKnownTags,
       Set<String> ignoredResources,
       DDAgentFeaturesDiscovery features,
+      HealthMetrics healthMetric,
       Sink sink,
       int maxAggregates,
       int queueSize) {
-    this(wellKnownTags, ignoredResources, features, sink, maxAggregates, queueSize, 10, SECONDS);
+    this(
+        wellKnownTags,
+        ignoredResources,
+        features,
+        healthMetric,
+        sink,
+        maxAggregates,
+        queueSize,
+        10,
+        SECONDS);
   }
 
   ConflatingMetricsAggregator(
       WellKnownTags wellKnownTags,
       Set<String> ignoredResources,
       DDAgentFeaturesDiscovery features,
+      HealthMetrics healthMetric,
       Sink sink,
       int maxAggregates,
       int queueSize,
@@ -103,6 +119,7 @@ public ConflatingMetricsAggregator(
     this(
         ignoredResources,
         features,
+        healthMetric,
         sink,
         new SerializingMetricWriter(wellKnownTags, sink),
         maxAggregates,
@@ -114,6 +131,7 @@ public ConflatingMetricsAggregator(
   ConflatingMetricsAggregator(
       Set<String> ignoredResources,
       DDAgentFeaturesDiscovery features,
+      HealthMetrics healthMetric,
       Sink sink,
       MetricWriter metricWriter,
       int maxAggregates,
@@ -126,6 +144,7 @@ public ConflatingMetricsAggregator(
     this.pending = new NonBlockingHashMap<>(maxAggregates * 4 / 3);
     this.keys = new NonBlockingHashMap<>();
     this.features = features;
+    this.healthMetrics = healthMetric;
     this.sink = sink;
     this.aggregator =
         new Aggregator(
@@ -215,17 +234,22 @@ public Future<Boolean> forceReport() {
   @Override
   public boolean publish(List<? extends CoreSpan<?>> trace) {
     boolean forceKeep = false;
+    int counted = 0;
     if (features.supportsMetrics()) {
       for (CoreSpan<?> span : trace) {
         boolean isTopLevel = span.isTopLevel();
         if (shouldComputeMetric(span)) {
           if (ignoredResources.contains(span.getResourceName().toString())) {
             // skip publishing all children
-            return false;
+            forceKeep = false;
+            break;
           }
+          counted++;
           forceKeep |= publish(span, isTopLevel);
         }
       }
+      healthMetrics.onClientStatTraceComputed(
+          counted, trace.size(), features.supportsDropping() && !forceKeep);
     }
     return forceKeep;
   }
@@ -314,18 +338,23 @@ public void close() {
 
   @Override
   public void onEvent(EventType eventType, String message) {
+    healthMetrics.onClientStatPayloadSent();
     switch (eventType) {
       case DOWNGRADED:
         log.debug("Agent downgrade was detected");
         disable();
+        healthMetrics.onClientStatDowngraded();
         break;
       case BAD_PAYLOAD:
         log.debug("bad metrics payload sent to trace agent: {}", message);
+        healthMetrics.onClientStatErrorReceived();
         break;
       case ERROR:
         log.debug("trace agent errored receiving metrics payload: {}", message);
+        healthMetrics.onClientStatErrorReceived();
         break;
       default:
+        break;
     }
   }
 

dd-trace-core/src/main/java/datadog/trace/common/metrics/MetricsAggregatorFactory.java

@@ -2,17 +2,20 @@
 
 import datadog.communication.ddagent.SharedCommunicationObjects;
 import datadog.trace.api.Config;
+import datadog.trace.core.monitor.HealthMetrics;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 public class MetricsAggregatorFactory {
   private static final Logger log = LoggerFactory.getLogger(MetricsAggregatorFactory.class);
 
   public static MetricsAggregator createMetricsAggregator(
-      Config config, SharedCommunicationObjects sharedCommunicationObjects) {
+      Config config,
+      SharedCommunicationObjects sharedCommunicationObjects,
+      HealthMetrics healthMetrics) {
     if (config.isTracerMetricsEnabled()) {
       log.debug("tracer metrics enabled");
-      return new ConflatingMetricsAggregator(config, sharedCommunicationObjects);
+      return new ConflatingMetricsAggregator(config, sharedCommunicationObjects, healthMetrics);
     }
     log.debug("tracer metrics disabled");
     return NoOpMetricsAggregator.INSTANCE;

dd-trace-core/src/main/java/datadog/trace/core/CoreTracer.java

@@ -316,6 +316,7 @@ public static class CoreTracerBuilder {
     private Map<String, String> baggageMapping;
     private int partialFlushMinSpans;
     private StatsDClient statsDClient;
+    private HealthMetrics healthMetrics;
     private TagInterceptor tagInterceptor;
     private boolean strictTraceWrites;
     private InstrumentationGateway instrumentationGateway;
@@ -419,8 +420,8 @@ public CoreTracerBuilder tagInterceptor(TagInterceptor tagInterceptor) {
       return this;
     }
 
-    public CoreTracerBuilder statsDClient(TagInterceptor tagInterceptor) {
-      this.tagInterceptor = tagInterceptor;
+    public CoreTracerBuilder healthMetrics(HealthMetrics healthMetrics) {
+      this.healthMetrics = healthMetrics;
       return this;
     }
 
@@ -522,6 +523,7 @@ public CoreTracer build() {
           baggageMapping,
           partialFlushMinSpans,
           statsDClient,
+          healthMetrics,
           tagInterceptor,
           strictTraceWrites,
           instrumentationGateway,
@@ -553,6 +555,7 @@ private CoreTracer(
       final Map<String, String> baggageMapping,
       final int partialFlushMinSpans,
       final StatsDClient statsDClient,
+      final HealthMetrics healthMetrics,
       final TagInterceptor tagInterceptor,
       final boolean strictTraceWrites,
       final InstrumentationGateway instrumentationGateway,
@@ -580,6 +583,7 @@ private CoreTracer(
         baggageMapping,
         partialFlushMinSpans,
         statsDClient,
+        healthMetrics,
         tagInterceptor,
         strictTraceWrites,
         instrumentationGateway,
@@ -610,6 +614,7 @@ private CoreTracer(
       final Map<String, String> baggageMapping,
       final int partialFlushMinSpans,
       final StatsDClient statsDClient,
+      final HealthMetrics healthMetrics,
       final TagInterceptor tagInterceptor,
       final boolean strictTraceWrites,
       final InstrumentationGateway instrumentationGateway,
@@ -698,11 +703,13 @@ private CoreTracer(
         config.isHealthMetricsEnabled()
             ? new MonitoringImpl(this.statsDClient, 10, SECONDS)
             : Monitoring.DISABLED;
-    healthMetrics =
-        config.isHealthMetricsEnabled()
-            ? new TracerHealthMetrics(this.statsDClient)
-            : HealthMetrics.NO_OP;
-    healthMetrics.start();
+    this.healthMetrics =
+        healthMetrics != null
+            ? healthMetrics
+            : (config.isHealthMetricsEnabled()
+                ? new TracerHealthMetrics(this.statsDClient)
+                : HealthMetrics.NO_OP);
+    this.healthMetrics.start();
     performanceMonitoring =
         config.isPerfMetricsEnabled()
             ? new MonitoringImpl(this.statsDClient, 10, SECONDS)
@@ -715,7 +722,7 @@ private CoreTracer(
             config.getScopeDepthLimit(),
             config.isScopeStrictMode(),
             profilingContextIntegration,
-            healthMetrics);
+            this.healthMetrics);
 
     externalAgentLauncher = new ExternalAgentLauncher(config);
 
@@ -740,7 +747,7 @@ private CoreTracer(
     if (writer == null) {
       this.writer =
           WriterFactory.createWriter(
-              config, sharedCommunicationObjects, sampler, singleSpanSampler, healthMetrics);
+              config, sharedCommunicationObjects, sampler, singleSpanSampler, this.healthMetrics);
     } else {
       this.writer = writer;
     }
@@ -757,22 +764,23 @@ private CoreTracer(
         && (config.isCiVisibilityAgentlessEnabled() || featuresDiscovery.supportsEvpProxy())) {
       pendingTraceBuffer = PendingTraceBuffer.discarding();
       traceCollectorFactory =
-          new StreamingTraceCollector.Factory(this, this.timeSource, healthMetrics);
+          new StreamingTraceCollector.Factory(this, this.timeSource, this.healthMetrics);
     } else {
       pendingTraceBuffer =
           strictTraceWrites
               ? PendingTraceBuffer.discarding()
               : PendingTraceBuffer.delaying(
-                  this.timeSource, config, sharedCommunicationObjects, healthMetrics);
+                  this.timeSource, config, sharedCommunicationObjects, this.healthMetrics);
       traceCollectorFactory =
           new PendingTrace.Factory(
-              this, pendingTraceBuffer, this.timeSource, strictTraceWrites, healthMetrics);
+              this, pendingTraceBuffer, this.timeSource, strictTraceWrites, this.healthMetrics);
     }
     pendingTraceBuffer.start();
 
     sharedCommunicationObjects.whenReady(this.writer::start);
 
-    metricsAggregator = createMetricsAggregator(config, sharedCommunicationObjects);
+    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.

dd-trace-core/src/main/java/datadog/trace/core/monitor/HealthMetrics.java

@@ -73,6 +73,24 @@ public void onFailedSend(
 
   public void onLongRunningUpdate(final int dropped, final int write, final int expired) {}
 
+  /**
+   * Report that a trace has been used to compute client stats.
+   *
+   * @param countedSpan the number of spans used for the stat computation
+   * @param totalSpan the number of total spans in the trace
+   * @param dropped true if the trace can be dropped. Note: the PayloadDispatcher also count this.
+   *     However, this counter will report how many p0 dropped we could achieve before that the span
+   *     got sampled.
+   */
+  public void onClientStatTraceComputed(
+      final int countedSpan, final int totalSpan, boolean dropped) {}
+
+  public void onClientStatPayloadSent() {}
+
+  public void onClientStatErrorReceived() {}
+
+  public void onClientStatDowngraded() {}
+
   /** @return Human-readable summary of the current health metrics. */
   public String summary() {
     return "";