Github user StephanEwen commented on a diff in the pull request:
https://github.com/apache/flink/pull/1133#discussion_r39955086
--- Diff:
flink-staging/flink-streaming/flink-streaming-core/src/main/java/org/apache/flink/streaming/runtime/operators/TriggerTimer.java
---
@@ -0,0 +1,119 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF 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.apache.flink.streaming.runtime.operators;
+
+import org.apache.flink.runtime.taskmanager.DispatcherThreadFactory;
+
+import java.util.concurrent.Executors;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.TimeUnit;
+
+/**
+ * A timer that triggers targets at a specific point in the future. This
timer executes single-threaded,
+ * which means that never more than one trigger will be executed at the
same time.
+ * <p>
+ * This timer generally maintains order of trigger events. This means that
for two triggers scheduled at
+ * different times, the one scheduled for the later time will be executed
after the one scheduled for the
+ * earlier time.
+ */
+public class TriggerTimer {
+
+ /** The thread group that holds all trigger timer threads */
+ public static final ThreadGroup TRIGGER_THREADS_GROUP = new
ThreadGroup("Triggers");
+
+ /** The executor service that */
+ private final ScheduledExecutorService scheduler;
+
+
+ /**
+ * Creates a new trigger timer, where the timer thread has the default
name "TriggerTimer Thread".
+ */
+ public TriggerTimer() {
+ this("TriggerTimer Thread");
+ }
+
+ /**
+ * Creates a new trigger timer, where the timer thread has the given
name.
+ *
+ * @param triggerName The name for the trigger thread.
+ */
+ public TriggerTimer(String triggerName) {
+ this.scheduler = Executors.newSingleThreadScheduledExecutor(
+ new
DispatcherThreadFactory(TRIGGER_THREADS_GROUP, triggerName));
+ }
+
+ /**
+ * Schedules a new trigger event. The trigger event will occur roughly
at the given timestamp.
+ * If the timestamp is in the past (or now), the trigger will be queued
for immediate execution. Note that other
+ * triggers that are to be executed now will be executed before this
trigger.
+ *
+ * @param target The target to be triggered.
+ * @param timestamp The timestamp when the trigger should occur, and
the timestamp given
+ * to the trigger-able target.
+ */
+ public void scheduleTriggerAt(Triggerable target, long timestamp) {
+ long delay = Math.max(timestamp - System.currentTimeMillis(),
0);
+
+ scheduler.schedule(
+ new TriggerTask(target, timestamp),
+ delay,
+ TimeUnit.MILLISECONDS);
+ }
+
+ /**
+ * Shuts down the trigger timer, canceling all pending triggers and
stopping the trigger thread.
+ */
+ public void shutdown() {
+ scheduler.shutdownNow();
+ }
+
+ /**
+ * The finalize method shuts down the timer. This is a fail-safe
shutdown, in case the original
+ * shutdown method was never called.
+ * <p>
+ * This should not be relied upon! It will cause shutdown to happen
much later than if manual
+ * shutdown is attempted, and cause threads to linger for longer than
needed.
+ */
+ @Override
+ @SuppressWarnings("FinalizeDoesntCallSuperFinalize")
+ protected void finalize() {
+ shutdown();
--- End diff --
Makes sense, will add this when merging...
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