[erlang-questions] time consuming operations inside gen_server

[Michael Truog]

On 12/12/2012 01:27 AM, Martin Dimitrov wrote:
> So, would it be appropriate to create a process that will do the time
> consuming operation and then notify the gen_server?

Yes, processes are cheap in Erlang.  There is no reason not to create a separate process for a task, that runs for awhile, to make sure the task doesn't stop your gen_server from processing its message queue.  You could do it with a erlang:spawn_link or supervisor:start_child, both of which are typically used in this type of a situation.  You want to avoid using erlang:process_flag(trap_exit, true), because it is simpler to have a supervisor manage the process, than have manual, custom supervisor-like functionality (within your gen_server).

There is another reason which long-running tasks often need separate processes, which is a separate concern.  If memory is used quickly, in a large quantity, you want the garbage collector to run quickly to free memory for other processes.  The short-lived process causes the garbage collector to collect when it dies (all the memory from the task), which would otherwise be a problem in a longer-lived process (since the memory would just accumulate, and would not be collected quickly).