WHMCS 5.2.2 + Plesk 11.0.9: Unable to Accept Orders

[Eric Pretorious]

When I manually accept the order (in WHMCS) (i.e., to "Automatically setup the product [in Plesk] when you manually accept a pending order") nginx reports this error:

502 Bad Gateway
nginx

Reloading the page displays the order along with an error - usually something like...

Order Accept Encountered Problems
Error Code: 1007 - Domain example.com already exists.

The order status (in WHMCS) has not changed but the client and the subscription has been created in the Plesk control panel.

Another user believes that the error is caused by Plesk restarting Apache:

The problem is caused by the WHMCS script trying to load the confirmation page at the exact second that apache is down while restarting. (Plesk always restarts apache after [adding] a domain).

Apache's log file (/var/log/httpd/error_log) confirms that Apache is restarted almost immediately after WHMCS begins the process of setting up the product in Plesk:

[Sat Mar 30 05:43:49 2013] [notice] caught SIGTERM, shutting down

Could the problem actually be caused by WHMCS being killed [by Apache restarting] while it's waiting for Plesk's confirmation?

 

[Eric Pretorious]

Bryan Apperson (of BitronicTech) recommended this solution:

http://www.bitronictech.net/knowledgebase/310/How-to-enable-Apache-graceful-restart-in-Plesk.html

...and I can confirm that even though nginx still complains "502 Bad Gateway nginx" Brian's solution works! i.e., backing up (to /whmcs/admin/orders.php) and refreshing the page show that the order was successfully accepted (i.e., the order status is now "Active").