🍒 Avoid race conditions on feature discovery during Writer creation

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

@@ -159,7 +159,7 @@ public DDAgentFeaturesDiscovery featuresDiscovery(Config config) {
               ret.discover(); // safe to run on same thread
             } else {
               // avoid performing blocking I/O operation on application thread
-              AgentTaskScheduler.INSTANCE.execute(ret::discover);
+              AgentTaskScheduler.INSTANCE.execute(ret::discoverIfOutdated);
             }
           }
           featuresDiscovery = ret;

dd-trace-core/src/main/java/datadog/trace/common/writer/WriterFactory.java

@@ -86,6 +86,7 @@ public static Writer createWriter(
     // The AgentWriter doesn't support the CI Visibility protocol. If CI Visibility is
     // enabled, check if we can use the IntakeWriter instead.
     if (DD_AGENT_WRITER_TYPE.equals(configuredType) && (config.isCiVisibilityEnabled())) {
+      featuresDiscovery.discoverIfOutdated();
       if (featuresDiscovery.supportsEvpProxy() || config.isCiVisibilityAgentlessEnabled()) {
         configuredType = DD_INTAKE_WRITER_TYPE;
       } else {
@@ -94,6 +95,7 @@ public static Writer createWriter(
       }
     }
     if (DD_AGENT_WRITER_TYPE.equals(configuredType) && (config.isLlmObsEnabled())) {
+      featuresDiscovery.discoverIfOutdated();
       if (featuresDiscovery.supportsEvpProxy() || config.isLlmObsAgentlessEnabled()) {
         configuredType = DD_INTAKE_WRITER_TYPE;
       } else {
@@ -186,6 +188,7 @@ private static RemoteApi createDDIntakeRemoteApi(
       SharedCommunicationObjects commObjects,
       DDAgentFeaturesDiscovery featuresDiscovery,
       TrackType trackType) {
+    featuresDiscovery.discoverIfOutdated();
     boolean evpProxySupported = featuresDiscovery.supportsEvpProxy();
     boolean useProxyApi =
         (evpProxySupported && TrackType.LLMOBS == trackType && !config.isLlmObsAgentlessEnabled())

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

@@ -669,9 +669,16 @@ private CoreTracer(
       this.writer = writer;
     }
 
+    DDAgentFeaturesDiscovery featuresDiscovery =
+        sharedCommunicationObjects.featuresDiscovery(config);
+
+    if (config.isCiVisibilityEnabled()) {
+      // ensure updated discovery and sync if the another discovery currently being done
+      featuresDiscovery.discoverIfOutdated();
+    }
+
     if (config.isCiVisibilityEnabled()
-        && (config.isCiVisibilityAgentlessEnabled()
-            || sharedCommunicationObjects.featuresDiscovery(config).supportsEvpProxy())) {
+        && (config.isCiVisibilityAgentlessEnabled() || featuresDiscovery.supportsEvpProxy())) {
       pendingTraceBuffer = PendingTraceBuffer.discarding();
       traceCollectorFactory =
           new StreamingTraceCollector.Factory(this, this.timeSource, healthMetrics);
@@ -732,8 +739,7 @@ private CoreTracer(
       if (config.isCiVisibilityAgentlessEnabled()) {
         addTraceInterceptor(DDIntakeTraceInterceptor.INSTANCE);
       } else {
-        DDAgentFeaturesDiscovery featuresDiscovery =
-            sharedCommunicationObjects.featuresDiscovery(config);
+        featuresDiscovery.discoverIfOutdated();
         if (!featuresDiscovery.supportsEvpProxy()) {
           // CI Test Cycle protocol is not available
           addTraceInterceptor(CiVisibilityApmProtocolInterceptor.INSTANCE);

dd-trace-core/src/test/groovy/datadog/trace/common/writer/WriterFactoryTest.groovy

@@ -1,5 +1,7 @@
 package datadog.trace.common.writer
 
+import static datadog.trace.api.config.TracerConfig.PRIORITIZATION_TYPE
+
 import datadog.communication.ddagent.DDAgentFeaturesDiscovery
 import datadog.communication.ddagent.SharedCommunicationObjects
 import datadog.trace.api.Config
@@ -10,10 +12,16 @@ import datadog.trace.common.writer.ddintake.DDEvpProxyApi
 import datadog.trace.common.writer.ddintake.DDIntakeApi
 import datadog.trace.core.monitor.HealthMetrics
 import datadog.trace.test.util.DDSpecification
-
+import groovy.json.JsonBuilder
 import java.util.stream.Collectors
-
-import static datadog.trace.api.config.TracerConfig.PRIORITIZATION_TYPE
+import okhttp3.Call
+import okhttp3.HttpUrl
+import okhttp3.MediaType
+import okhttp3.OkHttpClient
+import okhttp3.Protocol
+import okhttp3.Request
+import okhttp3.Response
+import okhttp3.ResponseBody
 
 class WriterFactoryTest extends DDSpecification {
 
@@ -27,19 +35,30 @@ class WriterFactoryTest extends DDSpecification {
     config.isCiVisibilityEnabled() >> true
     config.isCiVisibilityCodeCoverageEnabled() >> false
 
-    def agentFeaturesDiscovery = Mock(DDAgentFeaturesDiscovery)
-    agentFeaturesDiscovery.getEvpProxyEndpoint() >> DDAgentFeaturesDiscovery.V2_EVP_PROXY_ENDPOINT
-    agentFeaturesDiscovery.supportsContentEncodingHeadersWithEvpProxy() >> evpProxySupportsCompression
+    // Mock agent info response
+    def response = buildHttpResponse(hasEvpProxy, evpProxySupportsCompression, HttpUrl.parse(config.agentUrl + "/info"))
+
+    // Mock HTTP client that simulates delayed response for async feature discovery
+    def mockCall = Mock(Call)
+    def mockHttpClient = Mock(OkHttpClient)
+    mockCall.execute() >> {
+      // Add a delay
+      sleep(400)
+      return response
+    }
+    mockHttpClient.newCall(_ as Request) >> mockCall
 
+    // Create SharedCommunicationObjects with mocked HTTP client
     def sharedComm = new SharedCommunicationObjects()
-    sharedComm.setFeaturesDiscovery(agentFeaturesDiscovery)
+    sharedComm.okHttpClient = mockHttpClient
+    sharedComm.agentUrl = HttpUrl.parse(config.agentUrl)
     sharedComm.createRemaining(config)
 
     def sampler = Mock(Sampler)
 
     when:
-    agentFeaturesDiscovery.supportsEvpProxy() >> hasEvpProxy
     config.ciVisibilityAgentlessEnabled >> isCiVisibilityAgentlessEnabled
+
     def writer = WriterFactory.createWriter(config, sharedComm, sampler, null, HealthMetrics.NO_OP, configuredType)
 
     def apis
@@ -77,4 +96,28 @@ class WriterFactoryTest extends DDSpecification {
     "not-found"                                | false       | false                       | true                           | DDIntakeWriter       | [DDIntakeApi]      | true
     "not-found"                                | false       | false                       | false                          | DDAgentWriter        | [DDAgentApi]       | false
   }
+
+  Response buildHttpResponse(boolean hasEvpProxy, boolean evpProxySupportsCompression, HttpUrl agentUrl) {
+    def endpoints = []
+    if (hasEvpProxy && evpProxySupportsCompression) {
+      endpoints = [DDAgentFeaturesDiscovery.V4_EVP_PROXY_ENDPOINT]
+    } else if (hasEvpProxy) {
+      endpoints = [DDAgentFeaturesDiscovery.V2_EVP_PROXY_ENDPOINT]
+    } else {
+      endpoints = [DDAgentFeaturesDiscovery.V4_ENDPOINT]
+    }
+
+    def response = [
+      "version" : "7.40.0",
+      "endpoints"  : endpoints,
+    ]
+
+    def builder = new Response.Builder()
+      .code(200)
+      .message("OK")
+      .protocol(Protocol.HTTP_1_1)
+      .request(new Request.Builder().url(agentUrl.resolve("/info")).build())
+      .body(ResponseBody.create(MediaType.parse("application/json"), new JsonBuilder(response).toString()))
+    return builder.build()
+  }
 }