我一夜之间启动了我的实例，看看它是如何处理事情的，当我今天早上来的时候，我面临着一个
Exception in thread "pool-535-thread-7" java.lang.OutOfMemoryError: unable to create new native thread
at java.lang.Thread.start0(Native Method)
at java.lang.Thread.start(Thread.java:691)
at java.util.concurrent.ThreadPoolExecutor.addWorker(ThreadPoolExecutor.java:943)
at java.util.concurrent.ThreadPoolExecutor.processWorkerExit(ThreadPoolExecutor.java:992)[info] application - Connecting to server A
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
at java.lang.Thread.run(Thread.java:722)
我的代码的目的很简单：每 5 分钟，我连接到一个远程服务器列表，发送一个请求（通过套接字），就是这样。
这是我的代码：
我的“cron”任务：
/** will create a new instance of ExecutorService every 5 minutes, loading all the websites in the database to check their status **/
/** Maybe that's where the problem is ? I need to empty (GC ?) this ExecutorService ? **/
Akka.system().scheduler().schedule(
Duration.create(0, TimeUnit.MILLISECONDS), // Initial delay 0 milliseconds
Duration.create(5, TimeUnit.MINUTES), // Frequency 5 minutes
new Runnable() {
public void run() {
// We get the list of websites to check
Query<Website> query = Ebean.createQuery(Website.class, "WHERE disabled = false AND removed IS NULL");
query.order("created ASC");
List<Website> websites = query.findList(); // Can be 1, 10, 100, 1000. In my test case, I had only 9 websites.
ExecutorService executor = Executors.newFixedThreadPool(NTHREDS);
for (Website website : websites) {
CheckWebsite task = new CheckWebsite(website);
executor.execute(task);
}
// This will make the executor accept no new threads
// and finish all existing threads in the queue
executor.shutdown();
}
},
Akka.system().dispatcher()
);
我的 CheckWebsite 类：
public class CheckWebsite implements Runnable {
private Website website;
public CheckWebsite(Website website) {
this.website = website;
}
@Override
public void run() {
WebsiteLog log = website.checkState(); // This is where the request is made, I copy paste the code just after
if (log == null) {
Logger.error("OHOH, WebsiteLog should not be null for website.checkState() in CheckWebsite class :s");
return;
}
try {
log.save();
catch (Exception e) {
Logger.info ("An error occured :/");
Logger.info(e.getMessage());
e.printStackTrace();
}
}
}
我的checkState()方法Website.class：
public WebsiteLog checkState() {
// Since I use Socket and the connection can hang indefinitely, I use an other ExecutorService in order to limit the time spent
// The duration is defined via Connector.timeout, Which will be the next code.
ExecutorService executor = Executors.newFixedThreadPool(1);
Connector connector = new Connector(this);
try {
final long startTime = System.nanoTime();
Future<String> future = executor.submit(connector);
String response = future.get(Connector.timeout, TimeUnit.MILLISECONDS);
long duration = System.nanoTime() - startTime;
return PlatformLog.getLastOccurence(this, response, ((int) duration/ 1000000));
}
catch (Exception e) {
return PlatformLog.getLastOccurence(this, null, null);
}
}
这是Connector.class. 我在这里删除了无用的部分（如 Catches）：
public class Connector implements Callable<String> {
public final static int timeout = 2500; // WE use a timeout of 2.5s, which should be enough
private Website website;
public Connector(Website website) {
this.website = website;
}
@Override
public String call() throws Exception {
Logger.info ("Connecting to " + website.getAddress() + ":" + website.getPort());
Socket socket = new Socket();
try {
socket.connect(new InetSocketAddress(website.getIp(), website.getPort()), (timeout - 50));
BufferedReader input = new BufferedReader(new InputStreamReader(socket.getInputStream()));
String response = input.readLine();
socket.close();
return response;
}
catch (Exception e) {
e.printStackTrace();
throw e;
}
finally {
// I take the precaution to close the socket here in order to avoid a memory leak
// But if the previous ExecutorService force the close of this thread before
// I can't guarantee it will be closed :/
if (socket != null && !socket.isClosed()) {
socket.close();
}
}
}
}
我是 Java 多线程的新手，所以我可能犯了很大的错误。我怀疑某些领域可能是潜在的原因，但我缺乏知识需要我寻求您的帮助:)
总而言之，以下是潜力领域：
ExecutorService每 5 分钟创建一个新的。也许我可以重复使用旧的？或者我是否需要在完成后关闭当前的（如果是，如何？）。ExecutorService我创建一个将创建一个ExecutorService（在checkstate()方法中）的事实- 连接器类可以通过
ExecutorService运行它（暴力）停止的事实，如果它需要太长时间，导致套接字未关闭（然后是内存泄漏）？
此外，如您所见，线程“pool-535-thread-7”发生了异常，这意味着它不会很快发生。
我将 last_occured 检查存储在数据库中，并创建日志条目（在 中WebsiteLog），增量大约为 5 小时（因此，每 5 分钟，线程在大约 60 次调用后崩溃）。
更新：这是重新访问的 checkState 方法以包含关闭调用：
public PlatformLog checkState() {
ExecutorService executor = Executors.newFixedThreadPool(1);
Connector connector = new Connector(this);
String response = null;
Long duration = null;
try {
final long startTime = System.nanoTime();
Future<String> future = executor.submit(connector);
response = future.get(Connector.timeout, TimeUnit.MILLISECONDS);
duration = System.nanoTime() - startTime;
}
catch (Exception e) {}
executor.shutdown();
if (duration != null) {
return WebsiteLog.getLastOccurence(this, response, (duration.intValue()/ 1000000));
}
else {
return WebsiteLog.getLastOccurence(this, response, null);
}
}