Allow for disablement of tracing via remote config

dd-java-agent/testing/src/main/groovy/datadog/trace/agent/test/AgentTestRunner.groovy

@@ -171,6 +171,10 @@ abstract class AgentTestRunner extends DDSpecification implements AgentBuilder.L
   @SuppressWarnings('PropertyName')
   @Shared
   TraceConfig MOCK_DSM_TRACE_CONFIG = new TraceConfig() {
+    @Override
+    boolean isTraceEnabled() {
+      return true
+    }
     @Override
     boolean isRuntimeMetricsEnabled() {
       return true

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

@@ -540,6 +540,7 @@ private CoreTracer(
 
     this.dynamicConfig =
         DynamicConfig.create(ConfigSnapshot::new)
+            .setTracingEnabled(config.isTraceEnabled())
             .setRuntimeMetricsEnabled(config.isRuntimeMetricsEnabled())
             .setLogsInjectionEnabled(config.isLogsInjectionEnabled())
             .setDataStreamsEnabled(config.isDataStreamsEnabled())
@@ -725,6 +726,7 @@ private CoreTracer(
   public void rebuildTraceConfig(Config config) {
     dynamicConfig
         .initial()
+        .setTracingEnabled(config.isTraceEnabled())
         .setRuntimeMetricsEnabled(config.isRuntimeMetricsEnabled())
         .setLogsInjectionEnabled(config.isLogsInjectionEnabled())
         .setDataStreamsEnabled(config.isDataStreamsEnabled())
@@ -927,6 +929,9 @@ public AgentDataStreamsMonitoring getDataStreamsMonitoring() {
    * @param trace a list of the spans related to the same trace
    */
   void write(final List<DDSpan> trace) {
+    if (trace.isEmpty() || !trace.get(0).traceConfig().isTraceEnabled()) {
+      return;
+    }
     List<DDSpan> writtenTrace = interceptCompleteTrace(trace);
     if (writtenTrace.isEmpty()) {
       return;

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

@@ -5,6 +5,7 @@
 import static datadog.remoteconfig.tuf.RemoteConfigRequest.ClientInfo.CAPABILITY_APM_LOGS_INJECTION;
 import static datadog.remoteconfig.tuf.RemoteConfigRequest.ClientInfo.CAPABILITY_APM_TRACING_DATA_STREAMS_ENABLED;
 import static datadog.remoteconfig.tuf.RemoteConfigRequest.ClientInfo.CAPABILITY_APM_TRACING_SAMPLE_RATE;
+import static datadog.remoteconfig.tuf.RemoteConfigRequest.ClientInfo.CAPABILITY_APM_TRACING_TRACING_ENABLED;
 
 import com.squareup.moshi.Json;
 import com.squareup.moshi.JsonAdapter;
@@ -46,11 +47,11 @@ public TracingConfigPoller(DynamicConfig<?> dynamicConfig) {
   public void start(Config config, SharedCommunicationObjects sco) {
     this.startupLogsEnabled = config.isStartupLogsEnabled();
     ConfigurationPoller configPoller = sco.configurationPoller(config);
-    // TODO: Add CAPABILITY_APM_TRACING_TRACING_ENABLED flag when tracing_enabled is implemented for
-    // Remote config
+
     if (configPoller != null) {
       configPoller.addCapabilities(
-          CAPABILITY_APM_TRACING_SAMPLE_RATE
+          CAPABILITY_APM_TRACING_TRACING_ENABLED
+              | CAPABILITY_APM_TRACING_SAMPLE_RATE
               | CAPABILITY_APM_LOGS_INJECTION
               | CAPABILITY_APM_HTTP_HEADER_TAGS
               | CAPABILITY_APM_CUSTOM_TAGS
@@ -111,7 +112,6 @@ public void accept(ParsedConfigKey configKey, byte[] content, PollingRateHinter
             throw new IllegalArgumentException("env mismatch");
           }
         }
-
         receivedOverrides = true;
         applyConfigOverrides(overrides.libConfig);
         if (log.isDebugEnabled()) {
@@ -156,7 +156,7 @@ void applyConfigOverrides(LibConfig libConfig) {
     } else {
       GlobalLogLevelSwitcher.get().restore();
     }
-
+    maybeOverride(builder::setTracingEnabled, libConfig.tracingEnabled);
     maybeOverride(builder::setRuntimeMetricsEnabled, libConfig.runtimeMetricsEnabled);
     maybeOverride(builder::setLogsInjectionEnabled, libConfig.logsInjectionEnabled);
     maybeOverride(builder::setDataStreamsEnabled, libConfig.dataStreamsEnabled);
@@ -218,6 +218,9 @@ static final class ServiceTarget {
   }
 
   static final class LibConfig {
+    @Json(name = "tracing_enabled")
+    public Boolean tracingEnabled;
+
     @Json(name = "tracing_debug")
     public Boolean debugEnabled;
 

dd-trace-core/src/test/groovy/datadog/trace/core/CoreTracerTest.groovy

@@ -477,6 +477,51 @@ class CoreTracerTest extends DDCoreSpecification {
     """{"lib_config":{"tracing_tags": []}}""" | [:]
   }
 
+  def "verify configuration polling with tracing_enabled"() {
+    setup:
+    def key = ParsedConfigKey.parse("datadog/2/APM_TRACING/config_overrides/config")
+    def poller = Mock(ConfigurationPoller)
+    def sco = new SharedCommunicationObjects(
+      okHttpClient: Mock(OkHttpClient),
+      monitoring: Mock(Monitoring),
+      agentUrl: HttpUrl.get('https://example.com'),
+      featuresDiscovery: Mock(DDAgentFeaturesDiscovery),
+      configurationPoller: poller
+      )
+
+    def updater
+
+    when:
+    def tracer = CoreTracer.builder()
+      .sharedCommunicationObjects(sco)
+      .pollForTracingConfiguration()
+      .build()
+
+    then:
+
+    1 * poller.addListener(Product.APM_TRACING, _ as ProductListener) >> {
+      updater = it[1] // capture config updater for further testing
+    }
+    and:
+    tracer.captureTraceConfig().traceEnabled == true
+
+    when:
+    updater.accept(key, value.getBytes(StandardCharsets.UTF_8), null)
+    updater.commit()
+
+    then:
+    tracer.captureTraceConfig().traceEnabled == expectedValue
+
+    cleanup:
+    tracer?.close()
+
+    where:
+    value | expectedValue
+    """{"lib_config":{"tracing_enabled": false } } """ | false
+    """{"lib_config":{"tracing_enabled": true } } """  | true
+    """{"action": "enable", "lib_config": {"tracing_sampling_rate": null, "log_injection_enabled": null, "tracing_header_tags": null, "runtime_metrics_enabled": null, "tracing_debug": null, "tracing_service_mapping": null, "tracing_sampling_rules": null, "span_sampling_rules": null, "data_streams_enabled": null, "tracing_enabled": false}}""" | false
+  }
+
   def "test local root service name override"() {
     setup:
     def tracer = tracerBuilder().writer(new ListWriter()).serviceName("test").build()

internal-api/src/main/java/datadog/trace/api/DynamicConfig.java

@@ -92,7 +92,7 @@ public String toString() {
   }
 
   public final class Builder {
-
+    boolean tracingEnabled;
     boolean runtimeMetricsEnabled;
     boolean logsInjectionEnabled;
     boolean dataStreamsEnabled;
@@ -114,6 +114,7 @@ public final class Builder {
 
     Builder(Snapshot snapshot) {
 
+      this.tracingEnabled = snapshot.tracingEnabled;
       this.runtimeMetricsEnabled = snapshot.runtimeMetricsEnabled;
       this.logsInjectionEnabled = snapshot.logsInjectionEnabled;
       this.dataStreamsEnabled = snapshot.dataStreamsEnabled;
@@ -202,6 +203,11 @@ public Builder setTracingTags(Map<String, String> tracingTags) {
       return this;
     }
 
+    public Builder setTracingEnabled(boolean tracingEnabled) {
+      this.tracingEnabled = tracingEnabled;
+      return this;
+    }
+
     public Builder setPreferredServiceName(String preferredServiceName) {
       this.preferredServiceName = preferredServiceName;
       return this;
@@ -290,6 +296,7 @@ private static void maybePut(Map<String, Object> update, String key, Object valu
 
   /** Immutable snapshot of the configuration. */
   public static class Snapshot implements TraceConfig {
+    final boolean tracingEnabled;
     final boolean runtimeMetricsEnabled;
     final boolean logsInjectionEnabled;
     final boolean dataStreamsEnabled;
@@ -309,6 +316,7 @@ public static class Snapshot implements TraceConfig {
 
     protected Snapshot(DynamicConfig<?>.Builder builder, Snapshot oldSnapshot) {
 
+      this.tracingEnabled = builder.tracingEnabled;
       this.runtimeMetricsEnabled = builder.runtimeMetricsEnabled;
       this.logsInjectionEnabled = builder.logsInjectionEnabled;
       this.dataStreamsEnabled = builder.dataStreamsEnabled;
@@ -330,6 +338,11 @@ private static <K, V> Map<K, V> nullToEmpty(Map<K, V> mapping) {
       return null != mapping ? mapping : Collections.emptyMap();
     }
 
+    @Override
+    public boolean isTraceEnabled() {
+      return tracingEnabled;
+    }
+
     @Override
     public boolean isRuntimeMetricsEnabled() {
       return runtimeMetricsEnabled;

internal-api/src/main/java/datadog/trace/api/TraceConfig.java

@@ -7,6 +7,7 @@
 
 /** Snapshot of dynamic configuration; valid for the duration of a trace. */
 public interface TraceConfig {
+  boolean isTraceEnabled();
 
   boolean isRuntimeMetricsEnabled();
 

internal-api/src/main/java/datadog/trace/bootstrap/instrumentation/api/AgentTracer.java

@@ -1209,6 +1209,11 @@ public ByteBuffer serialize() {
   public static final class NoopTraceConfig implements TraceConfig {
     public static final NoopTraceConfig INSTANCE = new NoopTraceConfig();
 
+    @Override
+    public boolean isTraceEnabled() {
+      return false;
+    }
+
     @Override
     public boolean isRuntimeMetricsEnabled() {
       return false;