httpclient exception "org.apache.http.conn.ConnectionPoolTimeoutException: Timeout waiting for connection"

Question

I am trying to send request to my server, with following code. it failed at 3rd request, always.

import java.io.InputStreamReader;
import java.io.UnsupportedEncodingException;
import java.nio.charset.Charset;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.HttpStatus;
import org.apache.http.HttpVersion;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.entity.ContentType;
import org.apache.http.entity.StringEntity;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.impl.conn.tsccm.ThreadSafeClientConnManager;
import org.apache.http.params.BasicHttpParams;
import org.apache.http.params.CoreConnectionPNames;
import org.apache.http.params.HttpParams;
import org.apache.http.params.HttpProtocolParams;
import org.json.JSONException;
import org.json.JSONObject;
import org.json.JSONTokener;

public class HttpClientTest {
    private HttpClient client;

    public HttpClientTest() {
        HttpParams params = new BasicHttpParams();
        params.setParameter(CoreConnectionPNames.CONNECTION_TIMEOUT, 15000);  
        params.setParameter(CoreConnectionPNames.SO_TIMEOUT, 15000);

        HttpProtocolParams.setVersion(params, HttpVersion.HTTP_1_1);
        HttpProtocolParams.setContentCharset(params, "utf-8");
        HttpProtocolParams.setUseExpectContinue(params, true);
        ThreadSafeClientConnManager cm = new ThreadSafeClientConnManager();
        cm.setMaxTotal(100);
        client = new DefaultHttpClient(cm, params);

        while (true) {
            HttpPost mPost = new HttpPost("http://myip/myservice");

            JSONObject json = new JSONObject();
            try {
                json.put("serialNumber", "abcd");
            } catch (JSONException e1) {
                e1.printStackTrace();
            }
            StringEntity s = null;
            try {
                s = new StringEntity(json.toString());
            } catch (UnsupportedEncodingException e) {
                e.printStackTrace();
            }               
            s.setContentEncoding("UTF-8");
            s.setContentType("application/json");
            mPost.setEntity(s);

            JSONObject response = null;

            System.out.println("HttpClientTest ---> send post");
            HttpResponse mHttpResponse;
            try {
                mHttpResponse = client.execute(mPost);
                System.out.println("HttpClientTest  ---> get response");
                if(mHttpResponse.getStatusLine().getStatusCode() == HttpStatus.SC_OK){
                    HttpEntity entity = mHttpResponse.getEntity(); 
                    ContentType contentType = ContentType.getOrDefault(entity);
                    Charset charset = contentType.getCharset();
                    response = new JSONObject(new JSONTokener(new InputStreamReader(entity.getContent(), charset)));

                    System.out.println("HttpClientTest ---> get result:" + response.toString());
                } else {
                    mPost.abort();
                    break;
                }
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }

    public static void main(String[] args) {
        HttpClientTest t = new HttpClientTest();
    }
}

the exception as following:

org.apache.http.conn.ConnectionPoolTimeoutException: Timeout waiting for connection
    at org.apache.http.impl.conn.tsccm.ConnPoolByRoute.getEntryBlocking(ConnPoolByRoute.java:417)
    at org.apache.http.impl.conn.tsccm.ConnPoolByRoute$1.getPoolEntry(ConnPoolByRoute.java:300)
    at org.apache.http.impl.conn.tsccm.ThreadSafeClientConnManager$1.getConnection(ThreadSafeClientConnManager.java:224)
    at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:401)
    at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:820)
    at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:754)
    at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:732)
    at com.i360r.client.takeaway.network.HttpClientTest.<init>(HttpClientTest.java:68)
    at com.i360r.client.takeaway.network.HttpClientTest.main(HttpClientTest.java:88)

Answer 1

I had the same problem and I found the fix. This timeout is because of a connection leak. In my case, I'm using httpDelete method and not consuming the response. Instead, I'm checking the status of the response.

The fix is, the response entity needs to be consumed. In order to ensure the proper release of system resources, one must close the content stream associated with the entity.

So I used EntityUtils.consumeQuietly(response.getEntity()); which ensures that the entity content is fully consumed and the content stream, if exists, is closed.

Answer 2

I have fixed it! add mPost.releaseConnection() in finally blocks.

 try {
 } catch (Exception e) {
 } finally {
  mPost.releaseConnection();
 }

DO update package org.apache.httpcomponents to 4.2.1

Answer 3

Just put the line where you are getting your response inside try-with-resources and use CloseableHttpResponse instead of HttpResponse like this:

try(final CloseableHttpResponse mHttpResponse = client.execute(mPost);)
{
 System.out.println("HttpClientTest  ---> get response");
 ....remainder code

The mHttpResponse object will be auto consumed and closed for you

Hope this helps!

Answer 4

Use a CloseableHttpClient instead of HttpClient. You'll get a CloseableHttpResponse instead of a HttpResponse which support close(). So, when you are done with the response, just close it, no need to close the connection.

CloseableHttpResponse response = closableHttpClient.execute(httpPost, context);

...do what you need to do with it:

response.close();