Send initial telemetry in separate thread to reduce start-up latency.

dd-java-agent/src/main/java/datadog/trace/bootstrap/BootstrapInitializationTelemetry.java

@@ -1,11 +1,10 @@
 package datadog.trace.bootstrap;
 
 import datadog.json.JsonWriter;
-import java.io.IOException;
+import de.thetaphi.forbiddenapis.SuppressForbidden;
 import java.io.OutputStream;
 import java.util.ArrayList;
 import java.util.List;
-import java.util.concurrent.TimeUnit;
 
 /** Thread safe telemetry class used to relay information about tracer activation. */
 public abstract class BootstrapInitializationTelemetry {
@@ -179,7 +178,7 @@ public void finish() {
   }
 
   public interface JsonSender {
-    void send(byte[] payload) throws IOException;
+    void send(byte[] payload);
   }
 
   public static final class ForwarderJsonSender implements JsonSender {
@@ -190,19 +189,36 @@ public static final class ForwarderJsonSender implements JsonSender {
     }
 
     @Override
-    public void send(byte[] payload) throws IOException {
-      ProcessBuilder builder = new ProcessBuilder(forwarderPath, "library_entrypoint");
+    public void send(byte[] payload) {
+      ForwarderJsonSenderThread t = new ForwarderJsonSenderThread(forwarderPath, payload);
+      t.setDaemon(true);
+      t.start();
+    }
+  }
 
-      Process process = builder.start();
-      try (OutputStream out = process.getOutputStream()) {
-        out.write(payload);
-      }
+  public static final class ForwarderJsonSenderThread extends Thread {
+    private final String forwarderPath;
+    private final byte[] payload;
+
+    public ForwarderJsonSenderThread(String forwarderPath, byte[] payload) {
+      super("dd-forwarder-json-sender");
+      this.forwarderPath = forwarderPath;
+      this.payload = payload;
+    }
+
+    @SuppressForbidden
+    @Override
+    public void run() {
+      ProcessBuilder builder = new ProcessBuilder(forwarderPath, "library_entrypoint");
 
       try {
-        process.waitFor(1, TimeUnit.SECONDS);
-      } catch (InterruptedException e) {
-        // just for hygiene, reset the interrupt status
-        Thread.currentThread().interrupt();
+        Process process = builder.start();
+        try (OutputStream out = process.getOutputStream()) {
+          out.write(payload);
+        }
+      } catch (Throwable e) {
+        // We don't have a log manager here, so just print.
+        System.err.println("Failed to send telemetry: " + e.getMessage());
       }
     }
   }

dd-java-agent/src/test/groovy/datadog/trace/agent/InitializationTelemetryTest.groovy

@@ -21,7 +21,7 @@ class InitializationTelemetryTest extends Specification {
 
   def "normal start-up"() {
     when:
-    def result = InitializationTelemetryCheck.runTestJvm(null)
+    def result = InitializationTelemetryCheck.runTestJvm(null, false, "sleep")
 
     then:
     result.exitCode == 0
@@ -33,7 +33,7 @@ class InitializationTelemetryTest extends Specification {
     // agent initialization to fail.  However, we should catch the exception allowing the application
     // to run normally.
     when:
-    def result = InitializationTelemetryCheck.runTestJvm(InitializationTelemetryCheck.BlockByteBuddy)
+    def result = InitializationTelemetryCheck.runTestJvm(InitializationTelemetryCheck.BlockByteBuddy, false, "sleep")
 
     then:
     result.exitCode == 0

dd-java-agent/src/test/java/jvmbootstraptest/InitializationTelemetryCheck.java

@@ -20,7 +20,13 @@
  * <p>Checks edge cases where InitializationTelemetry is blocked by SecurityManagers
  */
 public class InitializationTelemetryCheck {
-  public static void main(String[] args) {}
+  public static void main(String[] args) throws InterruptedException {
+    // Emulates the real application performing work in main().
+    // That should give enough time to send initial telemetry from daemon thread.
+    if (args.length > 0 && "sleep".equals(args[0])) {
+      Thread.sleep(1000);
+    }
+  }
 
   /** Blocks the loading of the agent bootstrap */
   public static class BlockAgentLoading extends TestSecurityManager {
@@ -71,12 +77,20 @@ protected boolean checkFileExecutePermission(FilePermission perm, Object ctx, St
 
   public static final Result runTestJvm(Class<? extends TestSecurityManager> securityManagerClass)
       throws Exception {
-    return runTestJvm(securityManagerClass, false);
+    return runTestJvm(securityManagerClass, false, null);
   }
 
   public static final Result runTestJvm(
       Class<? extends TestSecurityManager> securityManagerClass, boolean printStreams)
       throws Exception {
+    return runTestJvm(securityManagerClass, printStreams, null);
+  }
+
+  public static final Result runTestJvm(
+      Class<? extends TestSecurityManager> securityManagerClass,
+      boolean printStreams,
+      String mainArgs)
+      throws Exception {
 
     File jarFile =
         IntegrationTestUtils.createJarFileWithClasses(requiredClasses(securityManagerClass));
@@ -95,7 +109,7 @@ public static final Result runTestJvm(
           IntegrationTestUtils.runOnSeparateJvm(
               InitializationTelemetryCheck.class.getName(),
               InitializationTelemetryCheck.jvmArgs(securityManagerClass),
-              InitializationTelemetryCheck.mainArgs(),
+              InitializationTelemetryCheck.mainArgs(mainArgs),
               InitializationTelemetryCheck.envVars(forwarderFile),
               jarFile,
               printStreams);
@@ -162,8 +176,12 @@ public static final String[] jvmArgs(Class<? extends TestSecurityManager> securi
     }
   }
 
-  public static final String[] mainArgs() {
-    return new String[] {};
+  public static final String[] mainArgs(String args) {
+    if (args == null) {
+      return new String[] {};
+    } else {
+      return args.split(",");
+    }
   }
 
   public static final Map<String, String> envVars(File forwarderFile) {

gradle/forbiddenApiFilters/main.txt

@@ -25,6 +25,6 @@ net.bytebuddy.matcher.ElementMatchers#isInterface()
 net.bytebuddy.matcher.ElementMatchers#isAbstract()
 
 # avoid System.out/err methods to prevent debug logging in production
-@defaultMessage Avoid using System.out/err to prevent excess logging. To override, add @SuppressMethod.
+@defaultMessage Avoid using System.out/err to prevent excess logging. To override, add @SuppressForbidden.
 java.lang.System#out
 java.lang.System#err