Tomcat 7 - Connection reset

Question

Hey I'm using Tomcat 7 and HttpClient 4.3.3. I am trying to connect to my Servlet with multiple threads but I often receive java.net.SocketException: Connection reset. When I suspend the Servlet's threads at the first line I'm still receiving the exception on my client. My question: is the cause of this problem maybe be linked with a too small number of maximum active connections? If not could please anyone help me with the problem?

try{

        // create new httpPost request with url of his class
        HttpPost httpPost = new HttpPost( "http://192.168.1.229:8080/test/test" );

        // create params and add it to httpPost
        List<NameValuePair> paramList = new ArrayList<NameValuePair>();
        paramList.add( new BasicNameValuePair( "json_req", format ) );
        UrlEncodedFormEntity formEntity = new UrlEncodedFormEntity( paramList );
        httpPost.setEntity( formEntity );

        // execute request and save response
        CloseableHttpResponse response = httpclient.execute( httpPost, context );

        HttpEntity entity = response.getEntity();
        InputStream content = entity.getContent();
        resp = content.available() > 0;

        content.close();
        response.close();
        // return the response
    }
    catch( Exception e ){
        e.printStackTrace();
    }

Exception:

java.net.SocketException: Connection reset
    at java.net.SocketInputStream.read(SocketInputStream.java:168)
    at org.apache.http.impl.io.SessionInputBufferImpl.streamRead(SessionInputBufferImpl.java:136)
    at org.apache.http.impl.io.SessionInputBufferImpl.fillBuffer(SessionInputBufferImpl.java:152)
    at org.apache.http.impl.io.SessionInputBufferImpl.readLine(SessionInputBufferImpl.java:270)
    at org.apache.http.impl.conn.DefaultHttpResponseParser.parseHead(DefaultHttpResponseParser.java:140)
    at org.apache.http.impl.conn.DefaultHttpResponseParser.parseHead(DefaultHttpResponseParser.java:57)
    at org.apache.http.impl.io.AbstractMessageParser.parse(AbstractMessageParser.java:260)
    at org.apache.http.impl.DefaultBHttpClientConnection.receiveResponseHeader(DefaultBHttpClientConnection.java:161)
    at sun.reflect.GeneratedMethodAccessor9.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at org.apache.http.impl.conn.CPoolProxy.invoke(CPoolProxy.java:138)
    at $Proxy0.receiveResponseHeader(Unknown Source)
    at org.apache.http.protocol.HttpRequestExecutor.doReceiveResponse(HttpRequestExecutor.java:271)
    at org.apache.http.protocol.HttpRequestExecutor.execute(HttpRequestExecutor.java:123)
    at org.apache.http.impl.execchain.MainClientExec.execute(MainClientExec.java:254)
    at org.apache.http.impl.execchain.ProtocolExec.execute(ProtocolExec.java:195)
    at org.apache.http.impl.execchain.RetryExec.execute(RetryExec.java:86)
    at org.apache.http.impl.execchain.RedirectExec.execute(RedirectExec.java:108)
    at org.apache.http.impl.client.InternalHttpClient.doExecute(InternalHttpClient.java:186)
    at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:82)
    at com.pribas.flightcacheservlet.servlet.HTTPThread.run(HTTPThread.java:69)
    at java.lang.Thread.run(Thread.java:662)

Code which starts the threads:

public static void main( String[] args ) throws Exception{
    FileUtil.init();

    PoolingHttpClientConnectionManager cm = new PoolingHttpClientConnectionManager();
    cm.setMaxTotal( 1000 );
    cm.setDefaultMaxPerRoute( 1000 );
    cm.setDefaultSocketConfig( SocketConfig.custom().setSoKeepAlive( true ).setSoReuseAddress( true ).setSoTimeout( 3000 ).build() );
    CloseableHttpClient httpClient = HttpClients.custom().setConnectionManager( cm ).build();

    HTTPThread.THREAD_COUNT = 300;
    HTTPThread.start = new CountDownLatch( HTTPThread.THREAD_COUNT );

    Thread[] threads = new Thread[ HTTPThread.THREAD_COUNT ];

    for( int i = 0; i < HTTPThread.THREAD_COUNT; i++ ){
        threads[ i ] = new Thread( new HTTPThread( httpClient ) );
    }

    for( Thread thread : threads ){
        thread.start();
    }

    for( Thread thread : threads ){
        thread.join();
    }

    httpClient.close();

    System.out.println( "Average response time: " + calAverage( HTTPThread.times ) + " milliseconds." );
}

Answer 1

Here is what the JavaDoc says about the mentioned exception:

Thrown to indicate that there is an error in the underlying protocol such as a TCP error

Through my personal experience, I faced such cases seems that it is not the other connection end (server) who closed the connection but your client. Otherwise you would receive another message: Connection reset by peer

This can happen due to many causes and in your case I guess it is related to the fact that you have not colsed the HttpClient instance at the end of your work unit; so try adding below line in the finally block of your try statement:

try
{
  ...
}
catch( Exception e )
{
  e.printStackTrace();
}
finally 
{
  httpClient.close(); //close the underlying client.
}

Update:

You may also need to enable the SO_KEEPALIVE to keep sockets alive:

    cm.setDefaultSocketConfig( 
        SocketConfig.custom().setSoKeepAlive(true)
          .setSoReuseAddress(true)
          .setSoTimeout(3000)
          .build());