Request entity too large 413 apache tomcat

Request entity too large

The requested resource /some/url/path/on/server does not allow request data with GET requests, or the amount of data provided in the request exceeds the capacity limit.

I get a corresponding error in my mod_jk.log file which is below. [Mon Oct 10 20:36:11 2011] [9834:0] [error] ajp_marshal_into_msgb::jk_ajp_common .c (415): failed appending the header value

I have a web farm running tomcat5, fronted by apache1.3 using the mod_jk connector. I started getting this erro开发者_JS百科r today on all the servers although no code changes were made today. The error seems to popup randomly. The same request doesn't always generate the error.

Can anyone explain the cause and why it would be random? I have seen recommendations to increase max_packet_size in server.xml. I want to understand the problem and the impact of the change before making it.