PoolingHttpClientConnectionManager的Java Apache HTTPClient TIME_WAIT性能问题

Question

We are using the Apache HTTPClient with a PoolingHttpClientConnectionManager and creating a connection pool of size 200 and 200 per route (as calling the same endpoint).

    PoolingHttpClientConnectionManager cm = new PoolingHttpClientConnectionManager(registryBuilder.build());
    cm.setMaxTotal(200);
    cm.setDefaultMaxPerRoute(200);

    httpClient = HttpClients.custom()
            .setConnectionManager(cm)
            .build();

The HTTPClient this is wrapped in a singleton class (so HTTPClient is being shared). I am then using this to make a GET request and respond with the Status Code and Body.

public ResponseEntity<String> get(String url, Map<String, String> headers) throws IOException {

    HttpGet httpget = new HttpGet(url);
    httpget.setConfig(requestConfig);
    headers.forEach(httpget::addHeader);

    ResponseHandler<ResponseEntity<String>> responseHandler =   response -> {
        int status = response.getStatusLine().getStatusCode();
        HttpEntity entity = response.getEntity();
        String body = entity != null ? EntityUtils.toString(entity) : null;
        return new ResponseEntity<>(body, HttpStatus.valueOf(status));
    };

    return httpClient.execute(httpget, responseHandler);
}

However are machine is under high CPU load and we are hitting around 30,000 TIME_WAIT sockets in netstat and can only reach around 250 TPS (our goal being 1000 TPS).

From the sounds of the 30,000 TIME_WAIT it looks like the connections are not being re-used?

Any ideas why?

Answer 1

It's the http keep-alive functionality that will make this to works. Normally it should be OK with your current code as keep-alive is enabled by default in Apache http-components .

So you need to be sure that :

• keep alive is enabled on the destination server (check the Keep-Alive http header)
• You reuse the httpClient
• The socket in TIME_WAIT are generated by you and not another process on the server

This is a piece of code that works for me, it's pretty much the same as yours :

DefaultHttpClient httpclient = new DefaultHttpClient();
PoolingClientConnectionManager pool = new   PoolingClientConnectionManager(httpclient.getConnectionManager().getSchemeRegistry());
pool.setMaxTotal(5000);
pool.setDefaultMaxPerRoute(1000);
HttpParams params = httpclient.getParams();
httpclient = new DefaultHttpClient(pool, params);

If it didn't works, maybe the server you connect to didn't support keep-alive (in this case it will never works) or support a non-standard keep-alive, in this latest case you can customize the keep-alive startegy of Apache http-components : https://hc.apache.org/httpcomponents-client-ga/tutorial/html/connmgmt.html - see the chapter 2.6 - Connection keep alive strategy

More info can be found here : http://www.baeldung.com/httpclient-connection-management