I have got 1000 dedicated Java threads where each thread polls a corresponding url every one second.
public class Poller {
public static Node poll(Node node) {
GetMethod method = null;
try {
HttpClient client = new HttpClient(new SimpleHttpConnectionManager(true));
......
} catch (IOException ex) {
ex.printStackTrace();
} finally {
method.releaseConnection();
}
}
}
The threads are run every one second:
for (int i=0; i <1000; i++) {
MyThread thread = threads.get(i) // threads is a static field
if(thread.isAlive()) {
// If the previous thread is still running, let it run.
} else {
thread.start();
}
}
The problem is if I run the job every one second I get random exceptions like these:
java.net.BindException: Address already in use
INFO httpclient.HttpMethodDirector: I/O exception (java.net.BindException) caught when processing request: Address already in use
INFO httpclient.HttpMethodDirector: Retrying request
But if I run the job every 2 seconds or more, everything runs fine.
I even tried shutting down the instance of SimpleHttpConnectionManager() using shutDown() with no effect.
If I do netstat, I see thousands of TCP connections in TIME_WAIT state, which means they are have been closed and are clearing up.
So to limit the no of connections, I tried using a single instance of HttpClient and use it like this:
public class MyHttpClientFactory {
private static MyHttpClientFactory instance = new HttpClientFactory();
private MultiThreadedHttpConnectionManager connectionManager;
private HttpClient client;
private HttpClientFactory() {
init();
}
public static HttpClientFactory getInstance() {
return instance;
}
public void init() {
connectionManager = new MultiThreadedHttpConnectionManager();
HttpConnectionManagerParams managerParams = new HttpConnectionManagerParams();
managerParams.setMaxTotalConnections(1000);
connectionManager.setParams(managerParams);
client = new HttpClient(connectionManager);
}
public HttpClient getHttpClient() {
if (client != null) {
return client;
} else {
init();
return client;
}
}
}
However after running for exactly 2 hours, it starts throwing 'too many open files' and eventually cannot do anything at all.
ERROR java.net.SocketException: Too many open files
INFO httpclient.HttpMethodDirector: I/O exception (java.net.SocketException) caught when processing request: Too many open files
INFO httpclient.HttpMethodDirector: Retrying request
I should be able to increase the no of connections allowed and make it work, but I would just be prolonging the evil. Any idea what is the best practise to use HttpClient in a situation like above?
Btw, I am still on HttpClient3.1.
