Java – Apache httpd Java Application

It's most likely that the lock-up is happening in a module rather than in Apache itself. Your setup sounds pretty minimal, so I'd suspect mod_jk as the culprit. If limiting MaxRequestsPerChild fixes the problem then I'd say that's an acceptable workaround. It's possible that a bug in the module is only triggered after a long time or many requests, and unless you're really keen on tracking this down then making it go away is probably good enough.

If you want to track it down then the first thing to do is configure CoreDumpDirectory to point to some location that the server user can write to. If you can get the offending process to leave a core file behind then it should help you track down the cause of the problem. You can find some hints on doing this in the Apache Debugging Guide.

With any *nix application, the easiest method is to query the binary itself. In the case of httpd, I'd imagine the process would be something like this:

$ whereis httpd
/usr/sbin/httpd
$ /usr/sbin/httpd -V
Server version: Apache/2.2.11 (Unix)
Server built:   Jun 17 2009 14:55:13
Server's Module Magic Number: 20051115:21
Server loaded:  APR 1.2.7, APR-Util 1.2.7
Compiled using: APR 1.2.7, APR-Util 1.2.7
Architecture:   64-bit
Server MPM:     Prefork
  threaded:     no
    forked:     yes (variable process count)
Server compiled with....
 -D APACHE_MPM_DIR="server/mpm/prefork"
 -D APR_HAS_SENDFILE
 -D APR_HAS_MMAP
 -D APR_HAVE_IPV6 (IPv4-mapped addresses enabled)
 -D APR_USE_FLOCK_SERIALIZE
 -D APR_USE_PTHREAD_SERIALIZE
 -D SINGLE_LISTEN_UNSERIALIZED_ACCEPT
 -D APR_HAS_OTHER_CHILD
 -D AP_HAVE_RELIABLE_PIPED_LOGS
 -D DYNAMIC_MODULE_LIMIT=128
 -D HTTPD_ROOT="/usr"
 -D SUEXEC_BIN="/usr/bin/suexec"
 -D DEFAULT_PIDLOG="/private/var/run/httpd.pid"
 -D DEFAULT_SCOREBOARD="logs/apache_runtime_status"
 -D DEFAULT_LOCKFILE="/private/var/run/accept.lock"
 -D DEFAULT_ERRORLOG="logs/error_log"
 -D AP_TYPES_CONFIG_FILE="/private/etc/apache2/mime.types"
 -D SERVER_CONFIG_FILE="/private/etc/apache2/httpd.conf"

As you can see - my OS X says the binary, if not directed otherwise, will use the config file: /private/etc/apache2/httpd.conf

If that doesn't help, perhaps Christopher's suggestion of find is the next step.