Guava线程池踩坑记录

Guava

google的并行化框架，研究不深，在此不班门弄斧，送上一个链接

坑描述

其实说坑有点儿委屈google了，因为根本不是guava的问题，是我自己的问题。长话短说，线程池记得关闭，记得关闭，记得关闭啊喂！！！重要的事情说三遍！！！

• 后果 ： 线程池没关你知道有多严重么？你肯定想不到，我把我们api的dev和beta server统统搞挂了啊，是server挂了，不是service挂了啊，哭！！！

• 细节：上代码

//max thread num : 20
final ExecutorService pool = Executors.newFixedThreadPool(20);
ListeningExecutorService service = MoreExecutors.listeningDecorator(pool);
// ListeningExecutorService executor = MoreExecutors.listeningDecorator(Executors.newFixedThreadPool(20));
List<Callable<Map<String, Object>>> tasks;

List<ListenableFuture<Map<String, Object>>> futures = Lists.newArrayList();
for(Map<String, Object> inputApp : appList) {
    ListenableFuture queryApp = service.submit(new Callable() {
        public Map<String, Object> call() {
            Map<String, Object>skyaidQueryRet = queryApp(inputApp, fromRedis);
            return  skyaidQueryRet;
        }
    });
    futures.add(queryApp);
}

final ListenableFuture<List<Map<String, Object>>> resultsFuture = Futures.successfulAsList(futures);
try {
    // block until all tasks are done
    retList = resultsFuture.get();
} catch (Exception e) {
    e.printStackTrace();
    pool.shutdown();
}
pool.shutdown();//重点就是这行

• 错误： 我一开始忘记加 pool.shutdown();这一句，直接导致的就是线程池中的task即使都执行完，资源并不会释放，最终回答道jvm的线程创建上限，导致不能创建任何新的线程，从而全线崩溃，甚至影响到了ssh到server都不能执行命令！

• throw error:

java.lang.RuntimeException: java.lang.reflect.InvocationTargetException
    at com.jfinal.aop.Invocation.invoke(Invocation.java:85)
    at ...//省略部分描述
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.reflect.InvocationTargetException
    at sun.reflect.GeneratedMethodAccessor99.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:497)
    at com.jfinal.aop.Invocation.invoke(Invocation.java:71)
    ... 23 more
Caused by: java.lang.OutOfMemoryError: unable to create new native thread
    at java.lang.Thread.start0(Native Method)
    at ...//省略部分描述
    at com.trendmicro.skyaid.controller.ArsController.v1(ArsController.java:35)
    ... 27 more

The end！