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From Divyaprakash Y <divyaprakas...@celstream.com>
Subject RE: Packet misses in Tomcat
Date Wed, 08 Jan 2014 09:06:35 GMT
-----Original Message-----
From: André Warnier [mailto:aw@ice-sa.com]
Sent: 08 January 2014 02:52
To: Tomcat Users List
Subject: Re: Packet misses in Tomcat

Christopher,

Christopher Schultz wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA256
>
> André,
>
> On 1/7/14, 5:09 AM, André Warnier wrote:
>> I do not pretend to know your system, nor your application, nor that
>> the following is a definite explanation.  But on the base of the
>> currently available data, I would say : - it is quite unlikely that
>> Tomcat 7 is randomly "dropping requests". If it was, then I would
>> imagine that this list would be overflowing with cries for help.
>> There is quite a bit of traffic on this list related to Tomcat 7, but
>> I don't recall seeing any significant number of issues mentioning
>> "dropped requests". - it also doesn't seem, from your
>> wireshark-related observations, that the requests are being lost
>> outside of Tomcat. - so I would say at this point, that the most
>> likely place for requests to disappear is in your own application.
>
> It seems that Tomcat is not logging the request in its access log, so
> it's more likely that the request is either malformed to such an
> extent that Tomcat rejects the request altogether or that the request
> never reaches Tomcat.
>
...
Hi. Of course I am going essentially by what the OP provided earlier as information, and he
has not provided much details on the "disappearing" requests themselves, or on the channel
through which these requests were reaching Tomcat.
But one thing that he did mention, is that these requests are similar - and even in general
the same - as other requests which do get processed normally.
As per his own words :

"For the query regarding "All requests", all requests do not disappear. More importantly,
sometimes all requests  reach the application when I POST same set of requests. To give a
rough picture, 1-2 requests fail in a set of 45-50 requests and this behaviour varies [The
request which failed in my one test cycle succeeds in another cycle]."

If we take this at face value, then it should not be so that these requests are so malformed
that Tomcat discards them without further ado.
Also - but maybe I'm wrong there - I would expect, if Tomcat discards a request for being
malformed - that something would appear in the Tomcat error log.  But according to the OP
it doesn't.
Finally - and there is a bit of an assumption on my part here - I assume that when the OP
says that he sees the request with Wireshark (prior to it "disappearing" in Tomcat), he was
running Wireshark on the Tomcat host itself.  That would make it unlikely that another external
component is at play.

All of the above led me to suspect that something in the application itself may be playing
a role here.

Of course, that all does not necessarily prove that some other component than Tomcat is not
dropping some packets/requests.
>
--

Clarifications for the missed information:
- Wireshark runs on the same machine where Tomcat runs
- Channel through which these requests were reaching Tomcat
- HTTP Chanel
- Can you describe your deployment? Are you accessing Tomcat directly via HTTP? What networking
components are between your test client(s) and Tomcat
- A war file with a servlet to POST the requests.
- There are 2 machines (LAN) where client and servers are installed. Client is used to send
the requests to Server.
- Disabled the firewall in the server machine
- Tomcat will be accessed directly via HTTP
- This issue occurs even if I use loopback address/localhost instead of Server IP Address
in the request URL (Install both client and server in the same machine).
- Tested with both "apache-tomcat-7.0.27.exe" and " apache-tomcat-7.0.42-windows-x86.zip"
- Also, Windows event logs will not have any entries when the requests getting missed.

Strange that this is happening only to me.

Overnight run of my application with Jetty Server(1167 requests) did not miss any requests.
So I am hoping that application is not contributing to the missing requests. I may be wrong
here.

Is there any way to get more logs on request processing in Tomcat?

Thanks.

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