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From Divyaprakash Y <divyaprakas...@celstream.com>
Subject RE: Packet misses in Tomcat
Date Fri, 10 Jan 2014 15:04:22 GMT


-----Original Message-----
From: Christopher Schultz [mailto:chris@christopherschultz.net]
Sent: 10 January 2014 03:46
To: Tomcat Users List
Subject: Re: Packet misses in Tomcat

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Hash: SHA256

Divyaprakash,

On 1/8/14, 4:06 AM, Divyaprakash Y wrote:
> -----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:

(I have re-ordered some of your responses so they make more logical sense to me):

> - There are 2 machines (LAN) where client and servers are installed.
> Client is used to send the requests to Server. - Wireshark runs on the
> same machine where Tomcat runs - 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).

> - A war file with a servlet to POST the requests.

What is the client?

Is it possible that this is something simple like the TCP backlog queue filling-up and the
OS is just discarding requests?

>

Christopher,

The client is nothing but a SOAP client which sends the SOAP packets at an interval of 30
seconds to the server. Looks like the situation of TCP backlog queue filling-up won't arise.

FYI, the issue arises only when I use APR connector whereas default BIO connector works fine
(both HTTP and HTTPS). I have not verified with NIO connector.

Any pointer?


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