Avoid performing blocking I/O operation on application thread

Author: mcculls

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

@@ -1,6 +1,7 @@
 package datadog.communication.ddagent;
 
 import static datadog.communication.ddagent.TracerVersion.TRACER_VERSION;
+import static datadog.trace.util.AgentThreadFactory.AGENT_THREAD_GROUP;
 
 import datadog.common.container.ContainerInfo;
 import datadog.common.socket.SocketUtils;
@@ -9,6 +10,7 @@
 import datadog.remoteconfig.ConfigurationPoller;
 import datadog.remoteconfig.DefaultConfigurationPoller;
 import datadog.trace.api.Config;
+import datadog.trace.util.AgentTaskScheduler;
 import java.util.concurrent.TimeUnit;
 import java.util.function.Supplier;
 import okhttp3.HttpUrl;
@@ -98,8 +100,11 @@ public DDAgentFeaturesDiscovery featuresDiscovery(Config config) {
               agentUrl,
               config.isTraceAgentV05Enabled(),
               config.isTracerMetricsEnabled());
-      if (!"true".equalsIgnoreCase(System.getProperty("dd.test.no.early.discovery"))) {
-        featuresDiscovery.discover();
+      if (AGENT_THREAD_GROUP.equals(Thread.currentThread().getThreadGroup())) {
+        featuresDiscovery.discover(); // safe to run on same thread
+      } else {
+        // avoid performing blocking I/O operation on application thread
+        AgentTaskScheduler.INSTANCE.execute(featuresDiscovery::discover);
       }
     }
     return featuresDiscovery;

dd-trace-core/src/main/java/datadog/trace/core/datastreams/DefaultDataStreamsMonitoring.java

@@ -136,21 +136,6 @@ public DefaultDataStreamsMonitoring(
 
   @Override
   public void start() {
-    if (features.getDataStreamsEndpoint() == null) {
-      features.discoverIfOutdated();
-    }
-
-    agentSupportsDataStreams = features.supportsDataStreams();
-    checkDynamicConfig();
-
-    if (!configSupportsDataStreams) {
-      log.debug("Data streams is disabled");
-    } else if (!agentSupportsDataStreams) {
-      log.debug("Data streams is disabled or not supported by agent");
-    }
-
-    nextFeatureCheck = timeSource.getCurrentTimeNanos() + FEATURE_CHECK_INTERVAL_NANOS;
-
     cancellation =
         AgentTaskScheduler.INSTANCE.scheduleAtFixedRate(
             new ReportTask(), this, bucketDurationNanos, bucketDurationNanos, TimeUnit.NANOSECONDS);
@@ -341,6 +326,22 @@ private StatsBucket getStatsBucket(final long timestamp, final String serviceNam
 
     @Override
     public void run() {
+
+      if (features.getDataStreamsEndpoint() == null) {
+        features.discoverIfOutdated();
+      }
+
+      agentSupportsDataStreams = features.supportsDataStreams();
+      checkDynamicConfig();
+
+      if (!configSupportsDataStreams) {
+        log.debug("Data streams is disabled");
+      } else if (!agentSupportsDataStreams) {
+        log.debug("Data streams is disabled or not supported by agent");
+      }
+
+      nextFeatureCheck = timeSource.getCurrentTimeNanos() + FEATURE_CHECK_INTERVAL_NANOS;
+
       Thread currentThread = Thread.currentThread();
       while (!currentThread.isInterrupted()) {
         try {