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Packet misses in Tomcat: not reach to application servlet but tomcat receives them

+3 votes

I have been experiencing missing packets during my application testing using Tomcat Server. If someone can help me to identify what is happening, it will be of great value.

Issue: Few packets do not reach the application servlet but tomcat receives them. The missing packets reach the HTTP layer and thereafter they disappear.

This issue is not frequent but occasionally consistent. For the POSTs of missing packet I am not able to find the entry in localhost_access_log.

Version: apache-tomcat-7.0.42
Application entry point: Servlet
OS: Windows 7(32 bit)

posted Jan 6, 2014 by Ahmed Patel

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How do you know that the packet reaches tomcat if there is no matching entry in localhost_access.log? Does all other access appear in this file?
I could see the packet in the wireshark capture and it has reached HTTP layer so I thought it has reached Tomcat; I may be wrong here. Also, as far as my observation, every hit to the application URLs was getting logged in local access log.
And is there anything in the Tomcat error logs ? (Or the Windows Event logs)

A HTTP request might be discarded by Tomcat for various reasons (*) before it is ever mapped to an application. In such a case, there is probably also no log of the request in the Access log. But I would expect some error message in the Tomcat error logs.

(*) Invalid HTTP request, incomplete request, etc..
If there are really packets being lost somewhere, then for POST requests the request size would not match the Content-length header, and that may be one of these cases.

I must say that the "packets lost" hypothesis sound a bit iffy to me.
This is TCP, which should detect missing packets and cause a client connection abort if it was the case. The invalid HTTP request being rejected by Tomcat sounds more probable to me.
I could not find anything (Exception) in tomcat std error log file or any file in the log folder. But I have not checked the Windows event logs. Will do that.

Regarding the content length, there is no mismatch as I have validated using Wireshark and also the same packets(In terms of structure) have reached the application previously.

W.r.t. the last point, I could see TCP ACK for the received packet in the wireshark and the packet has reached HTTP layer which goes missing thereafter.

Is there any configuration to get more logs on the operations happening during the mapping of request to the application?

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