gitlab: Setup gitlab-workhorse service

Gitlab-workhorse[1] is a service which offloads Ruby-on-Rails based
GitLab from long-running and slow requests. It is written in Go.

Now as we have unicorn service set up, we can setup gitlab-workhorse
service (which uses unicorn as authentication backend).

Gitlab-workhorse setup is easy - it is just one program and several
command line options to point to unicorn socket and to configure on
which unix socket gitlab-workhorse will listen itself.

NOTE we have to care that git and ruby to be on PATH when running
    gitlab-workhorse - because on e.g. git push'ing workhorse will run `git
    receive-pack` and a hook will be called which calls gitlab-shell,
    which is written in ruby.

NOTE2 promise to check whether gitlab-workhorse is alive is to ping it
    via URL to non-existent endpoint and check for proper 403 HTTP code
    returned.

[1] https://gitlab.com/gitlab-org/gitlab-workhorse

/cc @kazuhiko, @jerome

software/gitlab/instance-gitlab.cfg.in

@@ -18,6 +18,7 @@ parts =
     gitlab-work
     gitlab-shell-work
 
+    service-gitlab-workhorse
     service-unicorn
 
     service-postgresql
@@ -441,6 +442,49 @@ depend  =
 log     = ${redis:log}/*.log
 
 
+########################
+#   gitlab-workhorse   #
+########################
+[gitlab-workhorse-dir]
+recipe  = slapos.cookbook:mkdirectory
+srv     = ${directory:srv}/gitlab-workhorse
+
+[gitlab-workhorse]
+srv     = ${gitlab-workhorse-dir:srv}
+socket  = ${gitlab-workhorse:srv}/gitlab-workhorse.socket
+
+[service-gitlab-workhorse]
+recipe  = slapos.cookbook:wrapper
+wrapper-path    = ${directory:service}/gitlab-workhorse
+command-line    = {{ gitlab_workhorse }}
+    -listenNetwork unix
+    -listenAddr ${gitlab-workhorse:socket}
+    -authSocket ${unicorn:socket}
+# NOTE for profiling
+#   -pprofListenAddr ...
+
+# NOTE environment for:
+#   - git to be available on path
+#   - ruby to be available on path  (gitlab-workhorse -> gitlab-shell -> hooks  on push)
+environment =
+    PATH={{ git_location }}/bin:{{ ruby_location }}/bin:%(PATH)s
+
+depend  =
+    ${promise-gitlab-workhorse:recipe}
+
+
+[promise-gitlab-workhorse]
+<= promise-byurl
+# gitlab-workhorse works on repositories. Here we only check it accepts an
+# serves requests, so request is non-existent URL and expected code is 403
+url     = --unix-socket ${gitlab-workhorse:socket}  http:/non-existent
+http_code   = 403
+
+
+# gitlab-workhorse logs to stdout/stderr - logs are handled by slapos not us
+# [logrotate-entry-gitlab-workhorse]
+
+
 ######################
 #   unicorn worker   #
 ######################

software/gitlab/instance.cfg.in

@@ -35,11 +35,14 @@ context =
     raw curl_bin                    ${curl:location}/bin/curl
     raw dcron_bin                   ${dcron-output:crond}
     raw git                         ${git:location}/bin/git
+    raw git_location                ${git:location}
+    raw gitlab_workhorse            ${gitlab-workhorse:location}/gitlab-workhorse
     raw gunzip_bin                  ${gzip:location}/bin/gunzip
     raw gzip_bin                    ${gzip:location}/bin/gzip
     raw logrotate_bin               ${logrotate:location}/usr/sbin/logrotate
     raw postgresql_location         ${postgresql92:location}
     raw redis_binprefix             ${redis28:location}/bin
+    raw ruby_location               ${bundler-4gitlab:ruby-location}
 
 # config files
     raw config_ru_in                ${config.ru.in:target}