Ok, it goes without saying: “A2Billing is one of the most complete Calling Card systems in the Asterisk market today.” – on the other hand, it is also true that: “A2Billing is one of the most complex and convoluted pieces of code ever written!”.

The combination of the above makes for a fairly combustible mixture, especially if you have a big system. Now, I recently ran into an issue, where PHP was litterally eating up almost 512MB of ram, in order to run the A2Billing reports. In it self, that didn’t make much sense to me. However, after inspecting the code, and realizing that A2Billing uses GD in run-time to generate images out of thousands of CDR records, it made perfect sense that it may just be eating up memory.

So, increasing the memory on PHP to go up to 512MB of RAM helps, but creates an interesting probelm. Whenever Apache will invoke a script, it will automatically consume a shitload of RAM, and for each time I intiate a new query, it will spawn a new Apache instance, and consume the same amount of memory. That said, after 6 queries of 512MB, about 50% of the machines RAM was already eaten up – and Apache will not free it!

At this point, I had 2 choices:

  1. Go into the A2Billing code, change the GD code to work right or simply change it completely to something else (maybe flash).
  2. Work around the problem with a mix of proper IT practices.

I admit that I hate quite a lot of things (I won’t list these here); however; nothing ranks up the list as modifying someone elses code, when I know for fact that it will be unmaintainable in the future. So, I choose option number 2.

I’ve being playing alot with Lighttpd lately, and got some really nice performance from it. So, I said to myself, this would be a great test to see if Lighttpd+FastCGI can solve the problem here. I had to work my way around lighttpd to do what I wanted and verify that my FastCGI server in Lighttpd doesn’t consume all memory, however, here is what I got working with A2Billing, and really nice.

Step 1: Enable the required modules:

server.modules              = (
                               "mod_accesslog" )

Step 2: Enable the FastCGI Server

fastcgi.server             = ( ".php" =>
                               ( "localhost" =>
                                   "socket" => "/var/run/lighttpd/php-fastcgi.socket",
                                   "bin-path" => "/usr/bin/php-cgi",
                                   "idle-timeout" => 30,
                                   "max-procs" => 1,
                                   "min-procs" => 1

Step 3: Modify user permissions (required if you are using FreePBX)

server.username            = "asterisk"
server.groupname           = "asterisk"

Step 4: Setup authentication and authorization (optional)

#### auth module
## read authentication.txt for more info
auth.backend               = "htpasswd"
auth.backend.htpasswd.userfile = "/var/www/.htpasswd"
auth.require               = ( "/" =>
                                 "method"  => "basic",
                                 "realm"   => "A2Billing Management",
                                 "require" => "valid-user"

The above configuration made the interface spwan a single FastCGI, insuring that memory usage is never over utilized. I still need 512MB of RAM to run the scripts, but at least now it’s limited to only 512MB of RAM, out of a machine that has 16GB of RAM.