Hi,
it may come from servlet container if servlet call takes long time (by
default longer than 15mins).
You can disable this timeout by tuning request-timeout-seconds for
specific http-listener you're calling servlet on.
For example for http-listener-1 the command looks like:
asadmin set
configs.config.server-config.network-config.protocols.protocol.http-listener-1.http.request-timeout-seconds=-1
(request-timeout-seconds should work since Glassfish 3.0.1+)
WBR,
Alexey.