1 files changed, 115 insertions, 0 deletions
diff --git a/java/com/google/gerrit/pgm/util/RuntimeShutdown.java b/java/com/google/gerrit/pgm/util/RuntimeShutdown.java
new file mode 100644
index 0000000000..c5e856780f
--- /dev/null
+++ b/java/com/google/gerrit/pgm/util/RuntimeShutdown.java
@@ -0,0 +1,115 @@
+// Copyright (C) 2009 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.pgm.util;
+
+import com.google.common.flogger.FluentLogger;
+import java.util.ArrayList;
+import java.util.List;
+
+public class RuntimeShutdown {
+  private static final ShutdownCallback cb = new ShutdownCallback();
+
+  /** Add a task to be performed when graceful shutdown is requested. */
+  public static void add(Runnable task) {
+    if (!cb.add(task)) {
+      // If the shutdown has already begun we cannot enqueue a new
+      // task. Instead trigger the task in the caller, without any
+      // of our locks held.
+      //
+      task.run();
+    }
+  }
+
+  /** Wait for the JVM shutdown to occur. */
+  public static void waitFor() {
+    cb.waitForShutdown();
+  }
+
+  public static void manualShutdown() {
+    cb.manualShutdown();
+  }
+
+  private RuntimeShutdown() {}
+
+  private static class ShutdownCallback extends Thread {
+    private static final FluentLogger logger = FluentLogger.forEnclosingClass();
+
+    private final List<Runnable> tasks = new ArrayList<>();
+    private boolean shutdownStarted;
+    private boolean shutdownComplete;
+
+    ShutdownCallback() {
+      setName("ShutdownCallback");
+    }
+
+    boolean add(Runnable newTask) {
+      synchronized (this) {
+        if (!shutdownStarted && !shutdownComplete) {
+          if (tasks.isEmpty()) {
+            Runtime.getRuntime().addShutdownHook(this);
+          }
+          tasks.add(newTask);
+          return true;
+        }
+        // We don't permit adding a task once shutdown has started.
+        //
+        return false;
+      }
+    }
+
+    @Override
+    public void run() {
+      logger.atFine().log("Graceful shutdown requested");
+
+      List<Runnable> taskList;
+      synchronized (this) {
+        shutdownStarted = true;
+        taskList = tasks;
+      }
+
+      for (Runnable task : taskList) {
+        try {
+          task.run();
+        } catch (Exception err) {
+          logger.atSevere().withCause(err).log("Cleanup task failed");
+        }
+      }
+
+      logger.atFine().log("Shutdown complete");
+
+      synchronized (this) {
+        shutdownComplete = true;
+        notifyAll();
+      }
+    }
+
+    void manualShutdown() {
+      Runtime.getRuntime().removeShutdownHook(this);
+      run();
+    }
+
+    void waitForShutdown() {
+      synchronized (this) {
+        while (!shutdownComplete) {
+          try {
+            wait();
+          } catch (InterruptedException e) {
+            return;
+          }
+        }
+      }
+    }
+  }
+}