[Zen2] Introduce deterministic task queue

server/src/main/java/org/elasticsearch/cluster/coordination/FutureExecutor.java

@@ -0,0 +1,33 @@
+/*
+ * Licensed to Elasticsearch under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch licenses this file to you 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 org.elasticsearch.cluster.coordination;
+
+import org.elasticsearch.common.unit.TimeValue;
+
+/**
+ * Device which supports running a task after some delay has elapsed.
+ */
+public interface FutureExecutor {
+    /**
+     * Schedule the given task for execution after the given delay has elapsed.
+     */
+    void schedule(Runnable task, TimeValue delay);
+}
+

server/src/main/java/org/elasticsearch/threadpool/ThreadPool.java

@@ -362,9 +362,13 @@ public Runnable preserveContext(Runnable command) {
         return getThreadContext().preserveContext(command);
     }
 
-    public void shutdown() {
+    protected final void stopCachedTimeThread() {
         cachedTimeThread.running = false;
         cachedTimeThread.interrupt();
+    }
+
+    public void shutdown() {
+        stopCachedTimeThread();
         scheduler.shutdown();
         for (ExecutorHolder executor : executors.values()) {
             if (executor.executor() instanceof ThreadPoolExecutor) {
@@ -374,8 +378,7 @@ public void shutdown() {
     }
 
     public void shutdownNow() {
-        cachedTimeThread.running = false;
-        cachedTimeThread.interrupt();
+        stopCachedTimeThread();
         scheduler.shutdownNow();
         for (ExecutorHolder executor : executors.values()) {
             if (executor.executor() instanceof ThreadPoolExecutor) {