more log in ccm bridge

Author: SiyaoIsHiding

test-infra/src/main/java/com/datastax/oss/driver/api/testinfra/ccm/CcmBridge.java

@@ -299,6 +299,7 @@ public void start() {
       } catch (RuntimeException re) {
         // if something went wrong starting CCM, see if we can also dump the error
         dumpNodeStartupLogs();
+        dumpProcessTree();
         try {
           executeCheckLogError();
         } catch (RuntimeException checkLogErrorException) {
@@ -349,6 +350,26 @@ private void dumpNodeStartupLogs() {
     }
   }
 
+  /**
+   * Logs the process tree, to show where a node's launch script is stuck if it never got as far as
+   * starting the Cassandra JVM (no pid file and empty startup logs).
+   */
+  private void dumpProcessTree() {
+    try {
+      Process ps =
+          new ProcessBuilder("ps", "-eo", "pid,ppid,etime,stat,args", "--forest")
+              .redirectErrorStream(true)
+              .start();
+      String output = new String(ps.getInputStream().readAllBytes(), StandardCharsets.UTF_8);
+      ps.waitFor(10, TimeUnit.SECONDS);
+      LOG.error("Process tree:\n{}", output);
+    } catch (IOException e) {
+      LOG.error("Failed to dump process tree", e);
+    } catch (InterruptedException e) {
+      Thread.currentThread().interrupt();
+    }
+  }
+
   public void stop() {
     if (started.compareAndSet(true, false)) {
       execute("stop");