gitlab/unicorn: Automatically load all available CPUs by default

Automatically configure unicorn to spawn as much worker processes as
there are CPUs on the system by default.

GitLab omnibus pre-hardcodes this value default to 2 (which we copied)
and then also tweaks it this way in active code

    https://gitlab.com/gitlab-org/omnibus-gitlab/blob/8eda0933/files/gitlab-cookbooks/gitlab/attributes/default.rb#L230

which we also do here.

/cc @kazuhiko, @jerome

software/gitlab/instance-gitlab.cfg.in

@@ -45,6 +45,11 @@ cert    = ${slap-connection:cert-file}
 # autogenerated gitlab instance parameters
 <= gitlab-parameters
 
+# adjust/override some default settings:
+
+# automatically load all available CPUs
+configuration.unicorn_worker_processes  = {{ multiprocessing.cpu_count() + 1 }}
+
 
 
 # for convenience

software/gitlab/instance.cfg.in

@@ -22,6 +22,7 @@ rendered= $${buildout:directory}/instance-gitlab.cfg
 context =
     import os os
     import pwd pwd
+    import multiprocessing multiprocessing
 
     key eggs_directory          buildout:eggs-directory
     key develop_eggs_directory  buildout:develop-eggs-directory