Question

I am using httpcomponents 4.1.2 and the ThreadSafeClientConnManager runs out of connections. There does not appear to be any way to release a connection unlike the older commons HttpClient. My goal is to have a number of concurrent threads doing HTTP POSTs to a URL. Anyone have an idea of how to ‘release’ the connections? Or should i be doing it a different way?

import java.util.ArrayList;
import java.util.List;

import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.client.HttpClient;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.impl.conn.tsccm.ThreadSafeClientConnManager;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.protocol.HTTP;


public class HttpThread implements Runnable
{
    private static ThreadSafeClientConnManager cm;
    private static HttpClient httpClient;

    static
    {
        cm = new ThreadSafeClientConnManager();
        cm.setDefaultMaxPerRoute( 10 );
        cm.setMaxTotal( 100 );
        httpClient = new DefaultHttpClient( cm );
    }

    private String id;
    private int iterations;


    public HttpThread( String id, int iterations )
    {
        this.id= id;
        this.iterations = iterations;
    }


    @Override
    public void run()
    {       
        long start = System.currentTimeMillis();

        for( int i = 0; i < this.iterations; i++ )
        {
            HttpPost post = new HttpPost( "http://127.0.0.1:7001/in/iServlet" );            

            List<NameValuePair> nvps = new ArrayList<NameValuePair>();
            nvps.add( new BasicNameValuePair( "p1", "0123456789" ) );
            nvps.add( new BasicNameValuePair( "p2", "7" ) );
            nvps.add( new BasicNameValuePair( "p3", "80027-48taPS4lQVu7q6RjEA40kg-1207276200-75-2-1-0" ) );
            nvps.add( new BasicNameValuePair( "p4", "1-30--1-2-_60--2-Y-RED,XL__2-30-5-3-A-" ) );

            try
            {
                post.setEntity( new UrlEncodedFormEntity( nvps, HTTP.UTF_8 ) );

                System.out.println("before post: " + i);
                HttpResponse response = httpClient.execute( post );
                System.out.println("after post: " + i);
            }
            catch( Exception e )
            {
                e.printStackTrace();
            }
            finally
            {

            }
        }

        long stop = System.currentTimeMillis();
        System.out.println( this.id + "  finished: " + (stop - start) + " ms" );        
    }
}

With my driver being:

public class ThreadTest
{
    private ExecutorService executor = Executors.newCachedThreadPool(); 

    protected void spawnThreads( int numberOfThreads, int iterations )
    {
        for( int i = 1; i <= numberOfThreads; i++ )
        {
            HttpThread thread = new HttpThread( "thread-" + i, 100 );
            executor.execute( thread );

            System.out.println( "Launching: thread-" + i + " for: " + iterations + " iterations" );
        }
    }


    public static void main(String[] args)
    {
        ThreadTest t= new ThreadTest();
        t.spawnThreads( 1, 100 );
    }

}

My output is then:

Launching: thread-1 for: 100 iterations
before post: 0
after post: 0
before post: 1
after post: 1
before post: 2
after post: 2
before post: 3
after post: 3
before post: 4
after post: 4
before post: 5
after post: 5
before post: 6
after post: 6
before post: 7
after post: 7
before post: 8
after post: 8
before post: 9
after post: 9
before post: 10

Answer 1

You need to add the following code to the try block of your run method to free up the internal resources:

Entity entity = response.getEntity();
if(entity != null) entity.getContent().close();