Kadlabalu, Hareesh wrote:
Hi all,
This is regarding some tcp connections left with CLOSE_WAIT state when using
HttpClient 3.x.
I have done some googling for discussions around this and looked through the
library code around this area. Just want to validate what seems to be the
consensus:
1. When a program makes multiple http requests (hundreds of them), each one using a new instance of HttpClient, it is possible for some of the sockets to be left with CLOSE_WAIT state. This happens even when the HttoMethod is properly closed after use each time.
2. This happens because the HttpMethod's releaseConnection() does not close the underlying HttpConnection instance as this is available for other requests to reuse.
Correct.
Solutions:
1. Use MultiThreadedHttpConnectionManager and shut it down after use. This
will close all connections. I have tested it and it does work.
2. If for whatever reason the first solution cannot be used, another way is to close the connection explicitly using
HttpClient.getHttpConnectionManager().getConnection(hostconfig).close();
Correct, but I would recommend using
HttpConnectionManager#closeIdleConnections(0) instead, if you want to
close all idle connections without shutting down the connection manager
http://jakarta.apache.org/httpcomponents/httpclient-3.x/apidocs/org/apache/commons/httpclient/HttpConnectionManager.html#closeIdleConnections(long)
This works too. But is there a problem doing this? (I know all the reuse of
connections is not possible but is it harmful to use this?)
Are these conclusions right?
Yes, they are.
Cheers
Oleg
Attached below is a test program that produces CLOSE_WAIT when host is
running Weblogic10MP1 on Red Hat AS 4 U5. I have also seen this happen
on JBoss. This does not happen if I the host is tomcat 6, I am not sure
if there is a correlation.
Your advice is very much appreciated
Thanks
-hareesh
---------------Test code
public final class TestHttpClient
{
static String url;
public static void main( String [] args )
{
url = args[ 0 ];
int counter = args.length > 1 ? Integer.parseInt( args[ 1 ] ) : 100;
long waitTime = args.length > 2 ? Long.parseLong( args[ 2 ] ) : 0;
int batch = args.length > 3 ? Integer.parseInt( args[ 3 ] ) : 1;
try
{
for( int x = 0; x < batch; x++ )
{
for( int j = 0; j < counter; j++ )
{
_postData( x, j );
if( waitTime > 0 )
Thread.sleep( waitTime );
}
}
_waitForEver();
}
catch (Exception e)
{
e.printStackTrace();
}
}
private static void _postData( int batch, int counter ) throws IOException
{
HttpClient client = new HttpClient();
PostMethod postMethod = new PostMethod( url );
StringPart sPart = new StringPart( "ftcmd", "pingdb", "UTF-8" );
RequestEntity entity = new MultipartRequestEntity( new Part[] {sPart},
postMethod.getParams() );
postMethod.setRequestEntity( entity );
try
{
client.executeMethod( postMethod );
}
finally
{
postMethod.releaseConnection();
System.out.println("batch " + batch + " iteration " + counter + "
done");
}
}
private static void _waitForEver() throws InterruptedException
{
while( true )
{
Thread.sleep( 10000 );
System.out.println("Still alive..");
}
}
}
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