Support setting "manager" for Plack::Handler::FCGI in single-process mode

[ianburrell]

FCGI::ProcManager supports running in single-process mode when
n_processes is zero. It is useful (for harakiri support) to run
with proc manager in single-process mode.

This refactors _create_proc_manager method to create the manager
object. It uses different default manager class and number processes between
listen mode and single process mode. It keeps the old behavior for
single-process mode without manager. It would be possible to create proc manager by default or always.

[miyagawa]

I'm not sure what this patch does which the current code doesn't? Can't you just create a ProcManager object on your own with whatever configuration and set it to manager?

[ianburrell]

Problem is that the "manager" is not used in non-listen mode. The $proc_manager is only assigned and used when "listen" or $running_under_server_starter.

[ianburrell]

It would be fine if "manager" object had to be constructed externally and passed in for single-process mode.

Change would look like:

            # detach *before* the ProcManager inits
             $self->daemon_detach if $self->{daemonize};
-
-            $proc_manager->pm_manage;
         }
         elsif ($self->{daemonize}) {
             $self->daemon_detach;
         }
+    } elsif (blessed $self->{manager}) {
+        $proc_manager = $self->{manager};
     }

+    $proc_manager && $proc_manager->pm_manage;
+
     while ($request->Accept >= 0) {

[miyagawa]

Yeah that sounds more like a minimal change to make things that you want possible.

[ianburrell]

I updated the pull request with a simpler version that allows passing "manager" object in the web server single-process mode. It does depend on the caller constructing the FCGI::ProcManager with n_processes => 0. It doesn't require changing the proc manager construction and defaults.