Add shutdown hook to finish the spark application trace (#7357)

Add shutdown hook to finish the application span from a shutdown hook, in case where the JVM is shutdown using System.exit(code)

dd-java-agent/instrumentation/spark/src/main/java/datadog/trace/instrumentation/spark/AbstractDatadogSparkListener.java

@@ -10,6 +10,7 @@
 import datadog.trace.bootstrap.instrumentation.api.AgentSpan;
 import datadog.trace.bootstrap.instrumentation.api.AgentTracer;
 import datadog.trace.bootstrap.instrumentation.api.SpanLink;
+import datadog.trace.util.AgentThreadFactory;
 import de.thetaphi.forbiddenapis.SuppressForbidden;
 import java.io.PrintWriter;
 import java.io.StringWriter;
@@ -111,7 +112,7 @@ public abstract class AbstractDatadogSparkListener extends SparkListener {
   private int maxExecutorCount = 0;
   private long availableExecutorTime = 0;
 
-  private boolean applicationEnded = false;
+  private volatile boolean applicationEnded = false;
 
   public AbstractDatadogSparkListener(SparkConf sparkConf, String appId, String sparkVersion) {
     tracer = AgentTracer.get();
@@ -125,6 +126,22 @@ public AbstractDatadogSparkListener(SparkConf sparkConf, String appId, String sp
     databricksServiceName = getDatabricksServiceName(sparkConf, databricksClusterName);
     sparkServiceName = getSparkServiceName(sparkConf, isRunningOnDatabricks);
 
+    // If JVM exiting with System.exit(code), it bypass the code closing the application span
+    //
+    // Using shutdown hook to close the span, but it is only best effort:
+    // - no guarantee it will be executed before the tracer shuts down
+    // - no access to the exit code
+    Runtime.getRuntime()
+        .addShutdownHook(
+            AgentThreadFactory.newAgentThread(
+                AgentThreadFactory.AgentThread.DATA_JOBS_MONITORING_SHUTDOWN_HOOK,
+                () -> {
+                  if (!applicationEnded) {
+                    log.info("Finishing application trace from shutdown hook");
+                    finishApplication(System.currentTimeMillis(), null, 0, null);
+                  }
+                }));
+
     log.info("Created datadog spark listener: {}", this.getClass().getSimpleName());
   }
 

internal-api/src/main/java/datadog/trace/util/AgentThreadFactory.java

@@ -42,6 +42,8 @@ public enum AgentThread {
 
     PROCESS_SUPERVISOR("dd-process-supervisor"),
 
+    DATA_JOBS_MONITORING_SHUTDOWN_HOOK("dd-data-jobs-shutdown-hook"),
+
     DATA_STREAMS_MONITORING("dd-data-streams-monitor"),
 
     DEBUGGER_SNAPSHOT_SERIALIZER("dd-debugger-snapshot-serializer"),