[java] ensure the complete output is read #13091

Author: joerg1985

java/src/org/openqa/selenium/os/ExternalProcess.java

@@ -196,7 +196,8 @@ public ExternalProcess start() throws UncheckedIOException {
       try {
         CircularOutputStream circular = new CircularOutputStream(bufferSize);
 
-        new Thread(
+        Thread worker =
+            new Thread(
                 () -> {
                   // copyOutputTo might be system.out or system.err, do not to close
                   OutputStream output = new MultiOutputStream(circular, copyOutputTo);
@@ -212,10 +213,11 @@ public ExternalProcess start() throws UncheckedIOException {
                         Level.WARNING, "failed to copy the output of process " + process.pid(), ex);
                   }
                   LOG.log(Level.FINE, "completed to copy the output of process " + process.pid());
-                })
-            .start();
+                });
 
-        return new ExternalProcess(process, circular);
+        worker.start();
+
+        return new ExternalProcess(process, circular, worker);
       } catch (Throwable t) {
         // ensure we do not leak a process in case of failures
         try {
@@ -234,10 +236,12 @@ public static Builder builder() {
 
   private final Process process;
   private final CircularOutputStream outputStream;
+  private final Thread worker;
 
-  public ExternalProcess(Process process, CircularOutputStream outputStream) {
+  public ExternalProcess(Process process, CircularOutputStream outputStream, Thread worker) {
     this.process = process;
     this.outputStream = outputStream;
+    this.worker = worker;
   }
 
   /**
@@ -255,7 +259,13 @@ public boolean isAlive() {
   }
 
   public boolean waitFor(Duration duration) throws InterruptedException {
-    return process.waitFor(duration.toMillis(), TimeUnit.MILLISECONDS);
+    boolean exited = process.waitFor(duration.toMillis(), TimeUnit.MILLISECONDS);
+
+    if (exited) {
+      worker.join();
+    }
+
+    return exited;
   }
 
   public int exitValue() {
@@ -282,6 +292,7 @@ public void shutdown(Duration timeout) {
 
       try {
         if (process.waitFor(timeout.toMillis(), MILLISECONDS)) {
+          worker.join();
           return;
         }
       } catch (InterruptedException ex) {
@@ -290,5 +301,10 @@ public void shutdown(Duration timeout) {
     }
 
     process.destroyForcibly();
+    try {
+      worker.join();
+    } catch (InterruptedException ex) {
+      Thread.interrupted();
+    }
   }
 }