Receiving 500 error after create host on Rest API appears to complete successfully

I'm getting a strange 500 back from Foreman (actually, Apache) when I try
to add a host record in via the Rest API. I do my POST, and normally there
is no error. Occasionally, I'll get a 500 error back that says "execution
expired". When I look over the Apache logs, I can see the POST happen,
with the 500 error:

[26/Mar/2015:12:56:00 -0700] "POST /api/hosts HTTP/1.1" 500 47 "-" "python-requests/2.5.1
CPython/2.7.5 Linux/2.6.32-431.17.1.el6.x86_64"

Yet, in the Foreman production.log, it appears to POST without issue (no
error seen):

Started POST "/api/hosts" for at 2015-03-26 12:56:00 -0700
Processing by Api::V2::HostsController#create as JSON
Parameters: {"host"=>{"operatingsystem_id"=>4, "environment_id"=>1, "name"
=>"myvm", "medium_id"=>1, "subnet_id"=>1, "ip"=>"",
"hostgroup_id"=>6, "mac"=>"00:98:C2:0F:01:75", "architecture_id"=>1,
"host_parameters_attributes"=>[{"name"=>"vm_id", "value"=>"[FILTERED]",
"nested"=>"true"}], "domain_id"=>2, "ptable_id"=>1}, "apiv"=>"v2"}

Approximately 3 seconds later, my client gets the 500 message. I see no
other errors in the Apache error log, or the Foreman logs. No errors on
our Mysql server either. It appears to work. If I rerun the command, it

Has anyone run into something similar? Utilization, in terms of the # of
requests to Apache during this time, doesn't appear to be unusually high.
Over a one hour window, I was seeing 200-250 requests per minute, pretty
consistently, including the point at which the error occurred.