Tomcat离开time_wait连接

Question

we are using an Apache Sever as a front server an a Tomcat server for the backend. The frontend client is a java swing application. The protocol is hessian.

Sometimes we got a lot of small requests. When doing a "nestat -a" there are a lot of TIME_WAIT connections, which are blocking the server to open new connections. Only the connections to the tomcat seem to stay. The connections to the apache seem to be closed.

We are using a rewrite rule to forward the requests to the tomcat

RewriteEngine On
RewriteCond %{REQUEST_URI} .*\.servlet.*$
RewriteRule ^/(.*)$ http://localhost:8080/$1 [P]

Any ideas?

UPDATE:

Thanks for your advice ,

but it still doesn't work. Every stream is closed and there are still these TIME_WAIT's:

if (conn != null) {
    try {
        IOUtils.closeQuietly(conn.getInputStream());
    } catch (IOException e) {
        // do nothing
    }
    try {
        IOUtils.closeQuietly(conn.getOutputStream());
    } catch (Exception ex) {
        // do nothing
    }
    try {
        IOUtils.closeQuietly(((HttpURLConnection) conn).getErrorStream());
    } catch (Exception ex) {
        // do nothing
    }
}

if (conn instanceof HttpURLConnection) {
    ((HttpURLConnection) conn).disconnect();
}

Answer 1

Most likely you don't close the Input/Output Stream in the Swing application when making the request. From here :

If the result is an InputStream, it is very important that the InputStream.close() be put in an finally block, because Hessian will not close the underlying HTTP stream until all the data is read and the input stream is closed.

Answer 2

TIME_WAIT is a normal state of a recently closed connection, it will remain in it for a kernel-defined timeout. You did everything you can from the application's side.

If you have connections flicker too fast and experience a shortage of available ports, you could tweak your system's recycling of them. Huge amount of TIME_WAIT connections gives an overview for Linux as well as basic theory, Tuning Windows for TCP/IP performance lists corresponding Windows parameters with much breifer explanation.

Answer 3

It's not Tomcat, it's your operating system.

The OS is leaving connection in TIME_WAIT in order to avoid interference caused by too quick port reuse. Imagine packets from the old connection arriving late while a new connection is open in the same port.