✨ TimingWheel 代码优化。

mica-mqtt-core/src/main/java/net/dreamlu/iot/mqtt/core/util/timer/SystemTimer.java

@@ -58,6 +58,10 @@ public class SystemTimer implements Timer, Function<TimerTaskEntry, Void> {
 
 	private final ReentrantReadWriteLock.WriteLock writeLock = readWriteLock.writeLock();
 
+	public SystemTimer() {
+		this("SystemTimer");
+	}
+
 	public SystemTimer(String executeName) {
 		this(1L, 20, executeName);
 	}
@@ -72,28 +76,17 @@ public class SystemTimer implements Timer, Function<TimerTaskEntry, Void> {
 		timingWheel = new TimingWheel(tickMs, wheelSize, startMs, taskCounter, delayQueue);
 	}
 
-	/**
-	 * 添加一个任务，任务被包装为一个TimerTaskEntry
-	 *
-	 * @param timerTask TimerTask
-	 */
 	@Override
 	public void add(TimerTask timerTask) {
 		readLock.lock();
 		try {
+			// 通过任务的延时加上当前时间得到延时的具体时刻，作为定时任务的过期时间
 			addTimerTaskEntry(new TimerTaskEntry(timerTask, timerTask.getDelayMs() + Timer.getHiresClockMs()));
 		} finally {
 			readLock.unlock();
 		}
 	}
 
-	/**
-	 * Advance the internal clock, executing any tasks whose expiration has been
-	 * reached within the duration of the passed timeout.
-	 *
-	 * @param timeoutMs timeoutMs
-	 * @return whether or not any tasks were executed
-	 */
 	@Override
 	public boolean advanceClock(long timeoutMs) {
 		TimerTaskList bucket;
@@ -121,28 +114,20 @@ public class SystemTimer implements Timer, Function<TimerTaskEntry, Void> {
 		return true;
 	}
 
-	/**
-	 * Get the number of tasks pending execution
-	 *
-	 * @return the number of tasks
-	 */
 	@Override
 	public long size() {
 		return taskCounter.sum();
 	}
 
-	/**
-	 * Shutdown the timer service, leaving pending tasks unexpected
-	 */
 	@Override
 	public void shutdown() {
 		taskExecutor.shutdown();
 	}
 
 	private void addTimerTaskEntry(TimerTaskEntry timerTaskEntry) {
-		// 添加失败任务直接执行
+		// 尝试将任务加入时间轮
 		if (!timingWheel.add(timerTaskEntry)) {
-			// Already expired or cancelled
+			// 任务过期则执行任务，仅当 任务已经过期 或者 任务主动取消 才会进入此分支
 			if (!timerTaskEntry.cancelled()) {
 				taskExecutor.submit(timerTaskEntry.getTimerTask());
 			}

mica-mqtt-core/src/main/java/net/dreamlu/iot/mqtt/core/util/timer/Timer.java

@@ -6,8 +6,8 @@
  * (the "License"); you may not use this file except in compliance with
  * the License.  You may obtain a copy of the License at
  *
- *    <a href="http://www.apache.org/licenses/LICENSE-2.0">http://www.apache.org/licenses/LICENSE-2.0</a>
- *
+ * <a href="http://www.apache.org/licenses/LICENSE-2.0">http://www.apache.org/licenses/LICENSE-2.0</a>
+ * <p>
  * 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.
@@ -27,31 +27,29 @@ import java.util.concurrent.TimeUnit;
 public interface Timer {
 
 	/**
-	 * Add a new task to this executor. It will be executed after the task's delay
-	 * (beginning from the time of submission)
+	 * 添加新的任务到当前执行器（线程池），在任务过期后会执行任务。
 	 *
 	 * @param timerTask the task to add
 	 */
 	void add(TimerTask timerTask);
 
 	/**
-	 * Advance the internal clock, executing any tasks whose expiration has been
-	 * reached within the duration of the passed timeout.
+	 * 推进内部时钟，执行任何在走过的时间间隔内过期的任务
 	 *
 	 * @param timeoutMs timeoutMs
-	 * @return whether or not any tasks were executed
+	 * @return whether any tasks were executed
 	 */
 	boolean advanceClock(long timeoutMs);
 
 	/**
-	 * Get the number of tasks pending execution
+	 * 取得待执行的任务数量
 	 *
 	 * @return the number of tasks
 	 */
 	long size();
 
 	/**
-	 * Shutdown the timer service, leaving pending tasks unexecuted
+	 * 关闭定时器服务，待执行的任务将不会被执行
 	 */
 	void shutdown();
 

mica-mqtt-core/src/main/java/net/dreamlu/iot/mqtt/core/util/timer/TimerTask.java

@@ -19,7 +19,9 @@ package net.dreamlu.iot.mqtt.core.util.timer;
 
 
 /**
- * @author kafka、guest
+ * TimerTask
+ *
+ * @author kafka、guest、L.cm
  */
 public abstract class TimerTask implements Runnable {