![](/img/trans.png)
[英]Thread pool size of ThreadPoolExecutor passed into NioEventLoopGroup in Netty
[英]ThreadPoolExecutor - Changing the pool size even if no threads become idle
我需要一些幫助,以更好地了解ThreadPoolExecutor的工作方式。
我要處理1000項任務,這個數字在我的程序開始時就知道了。
我設置了一個ThreadPoolExecutor,並想即時更改它使用的線程數,這樣,如果服務器不是那么活躍(例如,晚上),我們就可以增加它可以使用的線程數。
增加線程數工作正常,我遇到的問題是,當我嘗試通過使用setCorePoolSize減少線程數時。
據我了解,該值僅在線程變為空閑時才更改。 由於需要不斷處理任務,因此該線程永遠不會變為空閑狀態,因此永遠不會關閉。
那我應該使用什么來減少線程數?
這是我的演示代碼:
package com.test.executortest;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
/**
*
* @author peter.marcoen
*/
public class ExecutorTest {
final static Logger log = LogManager.getLogger(ExecutorTest.class);
public static void main(String[] args) throws InterruptedException {
ThreadPoolExecutor x = new ThreadPoolExecutor(1, 100, 30, TimeUnit.DAYS, new LinkedBlockingQueue<Runnable>());
for (int i = 1; i <= 10; i++) {
RunnableTest r = new RunnableTest();
r.num = String.valueOf(i);
x.execute(r);
}
x.shutdown();
int i = 0;
while (!x.isTerminated()) {
i++;
log.debug("Active count: {}, Core pool size: {}, Maximum pool size: {}, Pool size: {}", x.getActiveCount(), x.getCorePoolSize(), x.getMaximumPoolSize(), x.getPoolSize());
if (i == 2) {
log.info("!!!! Setting core pool size to 2 !!!!");
x.setCorePoolSize(2);
} else if (i == 10) {
log.info("!!!! Setting core pool size to 1 !!!!");
x.setCorePoolSize(1);
}
Thread.sleep(1000);
}
}
}
使用RunnableTest睡眠5秒鍾:
package com.test.executortest;
import java.util.logging.Level;
import java.util.logging.Logger;
import org.apache.logging.log4j.LogManager;
/**
*
* @author peter.marcoen
*/
public class RunnableTest implements Runnable {
public String num;
final static org.apache.logging.log4j.Logger log = LogManager.getLogger(RunnableTest.class);
@Override
public void run() {
log.debug("Started parsing #{}", num);
try {
Thread.sleep(5000);
} catch (InterruptedException ex) {
Logger.getLogger(RunnableTest.class.getName()).log(Level.SEVERE, null, ex);
}
log.debug("Finished parsing #{}", num);
}
}
這就是輸出。 如您所見,即使將coreThreads設置為1,也始終會處理2個任務:
11:43:45.696 - Active count: 1, Core pool size: 1, Maximum pool size: 100, Pool size: 1
11:43:45.696 - Started parsing #1
11:43:46.710 - Active count: 1, Core pool size: 1, Maximum pool size: 100, Pool size: 1
11:43:46.710 - !!!! Setting core pool size to 2 !!!!
11:43:46.710 - Started parsing #2
11:43:47.724 - Active count: 2, Core pool size: 2, Maximum pool size: 100, Pool size: 2
11:43:48.738 - Active count: 2, Core pool size: 2, Maximum pool size: 100, Pool size: 2
11:43:49.738 - Active count: 2, Core pool size: 2, Maximum pool size: 100, Pool size: 2
11:43:50.705 - Finished parsing #1
11:43:50.705 - Started parsing #3
11:43:50.752 - Active count: 2, Core pool size: 2, Maximum pool size: 100, Pool size: 2
11:43:51.719 - Finished parsing #2
11:43:51.719 - Started parsing #4
11:43:51.766 - Active count: 2, Core pool size: 2, Maximum pool size: 100, Pool size: 2
11:43:52.780 - Active count: 2, Core pool size: 2, Maximum pool size: 100, Pool size: 2
11:43:53.794 - Active count: 2, Core pool size: 2, Maximum pool size: 100, Pool size: 2
11:43:54.795 - Active count: 2, Core pool size: 2, Maximum pool size: 100, Pool size: 2
11:43:54.795 - !!!! Setting core pool size to 1 !!!!
11:43:55.715 - Finished parsing #3
11:43:55.715 - Started parsing #5
11:43:55.809 - Active count: 2, Core pool size: 1, Maximum pool size: 100, Pool size: 2
11:43:56.729 - Finished parsing #4
11:43:56.729 - Started parsing #6
11:43:56.822 - Active count: 2, Core pool size: 1, Maximum pool size: 100, Pool size: 2
11:43:57.836 - Active count: 2, Core pool size: 1, Maximum pool size: 100, Pool size: 2
11:43:58.851 - Active count: 2, Core pool size: 1, Maximum pool size: 100, Pool size: 2
11:43:59.865 - Active count: 2, Core pool size: 1, Maximum pool size: 100, Pool size: 2
11:44:00.723 - Finished parsing #5
11:44:00.723 - Started parsing #7
11:44:00.879 - Active count: 2, Core pool size: 1, Maximum pool size: 100, Pool size: 2
11:44:01.739 - Finished parsing #6
11:44:01.739 - Started parsing #8
11:44:01.880 - Active count: 2, Core pool size: 1, Maximum pool size: 100, Pool size: 2
11:44:02.894 - Active count: 2, Core pool size: 1, Maximum pool size: 100, Pool size: 2
11:44:03.908 - Active count: 2, Core pool size: 1, Maximum pool size: 100, Pool size: 2
11:44:04.922 - Active count: 2, Core pool size: 1, Maximum pool size: 100, Pool size: 2
11:44:05.733 - Finished parsing #7
11:44:05.733 - Started parsing #9
11:44:05.936 - Active count: 2, Core pool size: 1, Maximum pool size: 100, Pool size: 2
11:44:06.749 - Finished parsing #8
11:44:06.749 - Started parsing #10
11:44:06.936 - Active count: 2, Core pool size: 1, Maximum pool size: 100, Pool size: 2
11:44:07.937 - Active count: 2, Core pool size: 1, Maximum pool size: 100, Pool size: 2
11:44:08.937 - Active count: 2, Core pool size: 1, Maximum pool size: 100, Pool size: 2
11:44:09.951 - Active count: 2, Core pool size: 1, Maximum pool size: 100, Pool size: 2
11:44:10.747 - Finished parsing #9
11:44:10.965 - Active count: 1, Core pool size: 1, Maximum pool size: 100, Pool size: 1
11:44:11.762 - Finished parsing #10
過去,我動態創建了一個輔助ThreadPoolExecutor
來從核心執行器中竊取任務,而不是動態地更改核心ThreadPoolExecutor
的大小(如您所發現的那樣,它有點不穩定)-這使我可以終止該輔助執行器而不影響核心執行者。 理想情況下,我們只能讓兩個執行者共享一個工作隊列,但這似乎引入了奇怪的並發錯誤,並且麻煩程度超過了它的價值-最好將隊列分開,並使用afterExecute
來保持輔助執行者的池填充。
public class AuxiliaryExecutor extends ThreadPoolExecutor {
private final AtomicBoolean shutdown = new AtomicBoolean(false);
private final BlockingQueue<Runnable> coreQueue;
private void pollAndExecute() {
try {
this.execute(coreQueue.poll());
} catch(NullPointerException e) {
this.execute(new Runnable() {
public void run() {
try {
this.execute(coreQueue.take());
} catch(InterruptedException e) {
return;
}
}
});
}
}
public AuxiliaryExecutor(ThreadPoolExecutor coreExecutor, int poolSize) {
super(poolSize, poolSize, 30L, TimeUnit.SECONDS, new ArrayBlockingQueue<>(poolSize));
this.coreQueue = coreExecutor.getQueue();
for(int i = 0; i < poolSize; i++) {
pollAndExecute();
}
}
@Override
protected void afterExecute(Runnable r, Throwable t) {
if(!shutdown.get()) {
pollAndExecute();
}
}
@Override
public void shutdown() {
shutdown.set(true);
}
}
如果要更改輔助執行器的大小,則可以關閉輔助執行器,然后將其替換為新的調整大小的執行器。
聲明:本站的技術帖子網頁,遵循CC BY-SA 4.0協議,如果您需要轉載,請注明本站網址或者原文地址。任何問題請咨詢:yoyou2525@163.com.