創建線程池注意、自定義線程池

1、

創建線程或線程池時請指定有意義的線程名稱，方便出錯時回溯。

創建線程池的時候請使用帶ThreadFactory的構造函數，並且提供自定義ThreadFactory實現或者使用第三方實現。

ThreadFactory namedThreadFactory = new ThreadFactoryBuilder()
.setNameFormat("demo-pool-%d").build();

ExecutorService singleThreadPool = new ThreadPoolExecutor(1, 1,
0L, TimeUnit.MILLISECONDS,
new LinkedBlockingQueue<Runnable>(1024), namedThreadFactory, new ThreadPoolExecutor.AbortPolicy());

singleThreadPool.execute(()-> System.out.println(Thread.currentThread().getName()));
singleThreadPool.shutdown();


public class TimerTaskThread extends Thread {
public TimerTaskThread(){
super.setName("TimerTaskThread"); …
}

 

2、

線程池不允許使用Executors去創建，而是通過ThreadPoolExecutor的方式，這樣的處理方式讓寫的同學更加明確線程池的運行規則，規避資源耗盡的風險。

說明：Executors返回的線程池對象的弊端如下：

1）FixedThreadPool和SingleThreadPool:
  允許的請求隊列長度為Integer.MAX_VALUE，可能會堆積大量的請求，從而導致OOM。
2）CachedThreadPool:
  允許的創建線程數量為Integer.MAX_VALUE，可能會創建大量的線程，從而導致OOM。

Positive example 1：

//org.apache.commons.lang3.concurrent.BasicThreadFactory
ScheduledExecutorService executorService = new ScheduledThreadPoolExecutor(1,
new BasicThreadFactory.Builder().namingPattern("example-schedule-pool-%d").daemon(true).build());

Positive example 2：

ThreadFactory namedThreadFactory = new ThreadFactoryBuilder()
.setNameFormat("demo-pool-%d").build();


//Common Thread Pool
ExecutorService pool = new ThreadPoolExecutor(5, 200,
0L, TimeUnit.MILLISECONDS,
new LinkedBlockingQueue<Runnable>(1024),
 namedThreadFactory, 
new ThreadPoolExecutor.AbortPolicy());


pool.execute(()-> System.out.println(Thread.currentThread().getName()));
pool.shutdown();//gracefully shutdown

 

Positive example 3：

<bean id="userThreadPool"
class="org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor">
<property name="corePoolSize" value="10" />
<property name="maxPoolSize" value="100" />
<property name="queueCapacity" value="2000" />

<property name="threadFactory" value= threadFactory />
<property name="rejectedExecutionHandler">
<ref local="rejectedExecutionHandler" />
</property>
</bean>
//in code
userThreadPool.execute(thread);

3、

線程資源必須通過線程池提供，不允許在應用中自行顯式創建線程。

說明：

使用線程池的好處是減少在創建和銷毀線程上所花的時間以及系統資源的開銷，解決資源不足的問題。

如果不使用線程池，有可能造成系統創建大量同類線程而導致消耗完內存或者“過度切換”的問題。

ThreadFactory namedThreadFactory = new ThreadFactoryBuilder()
.setNameFormat("demo-pool-%d").build();


ExecutorService singleThreadPool = new ThreadPoolExecutor(1, 1,
0L, TimeUnit.MILLISECONDS,
new LinkedBlockingQueue<Runnable>(1024),
 namedThreadFactory, 
new ThreadPoolExecutor.AbortPolicy());


singleThreadPool.execute(()-> System.out.println(Thread.currentThread().getName()));
singleThreadPool.shutdown();