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From Adhavan Mathiyalagan <adhav....@gmail.com>
Subject Re: CLOSE_WAIT between Application (Tomcat) and Apache HTTPD
Date Thu, 11 May 2017 09:03:44 GMT
Thanks Guido !

On Thu, May 11, 2017 at 12:02 PM, Jäkel, Guido <G.Jaekel@dnb.de> wrote:

> Dear Adhavan,
>
> I think this is quiet normal, because the browser clients "in front" will
> reuse connections (using keep-alive at TCP level) but an in-between load
> balancer may be not work or configured in this way and will use a new
> connection for each request to the backend.
>
> Then, you'll see a lot of sockets in the TCP/IP closedown workflow between
> the load balancer and the backend server. Pleases refer to TCP/IP that the
> port even for a "well closed connection" will be hold some time to handle
> late (duplicate) packets. Think about a duplicated, delayed RST packet -
> this should not close the next connection to this port.
>
> Because this situation is very unlikely or even impossible on a local area
> network, you may adjust the TCP stack setting of your server to use much
> lower protection times (in the magnitude of seconds) and also adjust
> others. And at Linux, you may also expand the range of ports used for
> connections.
>
> BTW: If you have a dedicated stateful packet inspecting firewall between
> your LB and the server, you also have to take a look on this.
>
>
> Said that, one more cent about the protocol between the LB and the Tomcat:
> I don’t know about HTTP, but if you use AJP (with mod_jk) you may configure
> it to keep and reuse connections to the Tomcat backend(s).
>
> Guido
>
> >-----Original Message-----
> >From: Adhavan Mathiyalagan [mailto:adhav.vit@gmail.com]
> >Sent: Wednesday, May 10, 2017 6:32 PM
> >To: Tomcat Users List
> >Subject: CLOSE_WAIT between Application (Tomcat) and Apache HTTPD
> >
> >Team,
> >
> >Tomcat version : 8.0.18
> >
> >Apache HTTPD version : 2.2
> >
> >
> >There are lot of CLOSE_WAIT connections being created at the
> >Application(tomcat)  ,when the traffic is routed through the Apache HTTPD
> >load balancer to the Application running over tomcat container. This leads
> >to slowness of the port where the Application is running and eventually
> the
> >application is not accessible through that particular PORT.
> >
> >In case of the traffic directly reaching the Application PORT without
> HTTPD
> >(Load balancer) there is no CLOSE_WAIT connections created and
> application
> >can handle the load seamlessly.
> >
> >Thanks in advance for the support.
> >
> >Regards,
> >Adhavan.M
>

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