unicorn metrics not collected by prometheus

Summary

I can't get the unicorn metrics to appear in the grafana omnibus dashboard event which the unicorn exporter enabled and a scrape_config added to specifically scrape the endpoint for unicorn exporter

Steps to reproduce

Added this to gitlab.rb file :

unicorn['exporter_enabled'] = true
prometheus['scrape_configs'] = [
	{
		'job_name': 'unicorn',
		'static_configs' => [
			'targets' => ['127.0.0.1:8083'],
		],
	},
]

Example Project

Latest gitlab omnibus

What is the current bug behavior?

Gauge in dashboard remains empty/null

What is the expected correct behavior?

Something to be displayed in the gauge

Output of checks

Results of GitLab environment info

Expand for output related to GitLab environment info

System information
System:		Debian 8.11
Current User:	git
Using RVM:	no
Ruby Version:	2.6.3p62
Gem Version:	2.7.9
Bundler Version:1.17.3
Rake Version:	12.3.3
Redis Version:	3.2.12
Git Version:	2.22.0
Sidekiq Version:5.2.7
Go Version:	unknown
GitLab information
Version:	12.4.2
Revision:	393a5bdafa2
Directory:	/opt/gitlab/embedded/service/gitlab-rails
DB Adapter:	PostgreSQL
DB Version:	10.9
URL:		https://gitlab.itspire.fr
HTTP Clone URL:	https://gitlab.itspire.fr/some-group/some-project.git
SSH Clone URL:	git@gitlab.itspire.fr:some-group/some-project.git
Using LDAP:	no
Using Omniauth:	yes
Omniauth Providers:
GitLab Shell
Version:	10.2.0
Repository storage paths:

• default: /opt/gitlab/git-data/repositories GitLab Shell path: /opt/gitlab/embedded/service/gitlab-shell Git: /opt/gitlab/embedded/bin/git

Results of GitLab application Check

Expand for output related to the GitLab application check

Checking GitLab subtasks ...
Checking GitLab Shell ...
GitLab Shell: ... GitLab Shell version >= 10.2.0 ? ... OK (10.2.0)
Running /opt/gitlab/embedded/service/gitlab-shell/bin/check
Internal API available: OK
Redis available via internal API: OK
gitlab-shell self-check successful
Checking GitLab Shell ... Finished
Checking Gitaly ...
Gitaly: ... default ... OK
Checking Gitaly ... Finished
Checking Sidekiq ...
Sidekiq: ... Running? ... yes
Number of Sidekiq processes ... 1
Checking Sidekiq ... Finished
Checking Incoming Email ...
Incoming Email: ... Reply by email is disabled in config/gitlab.yml
Checking Incoming Email ... Finished
Checking LDAP ...
LDAP: ... LDAP is disabled in config/gitlab.yml
Checking LDAP ... Finished
Checking GitLab App ...
Git configured correctly? ... yes
Database config exists? ... yes
All migrations up? ... yes
Database contains orphaned GroupMembers? ... no
GitLab config exists? ... yes
GitLab config up to date? ... yes
Log directory writable? ... yes
Tmp directory writable? ... yes
Uploads directory exists? ... yes
Uploads directory has correct permissions? ... yes
Uploads directory tmp has correct permissions? ... yes
Init script exists? ... skipped (omnibus-gitlab has no init script)
Init script up-to-date? ... skipped (omnibus-gitlab has no init script)
Projects have namespace: ...
4/1 ... yes
4/2 ... yes
4/3 ... yes
4/4 ... yes
4/5 ... yes
4/8 ... yes
4/9 ... yes
4/10 ... yes
4/16 ... yes
5/19 ... yes
5/20 ... yes
4/21 ... yes
5/22 ... yes
5/23 ... yes
5/24 ... yes
5/25 ... yes
5/26 ... yes
5/27 ... yes
5/28 ... yes
4/31 ... yes
5/32 ... yes
6/34 ... yes
6/36 ... yes
5/37 ... yes
5/38 ... yes
5/39 ... yes
5/40 ... yes
5/41 ... yes
4/42 ... yes
4/43 ... yes
13/44 ... yes
6/45 ... yes
4/46 ... yes
4/47 ... yes
5/48 ... yes
4/50 ... yes
6/51 ... yes
6/52 ... yes
Redis version >= 2.8.0? ... yes
Ruby version >= 2.5.3 ? ... yes (2.6.3)
Git version >= 2.22.0 ? ... yes (2.22.0)
Git user has default SSH configuration? ... yes
Active users: ... 4
Is authorized keys file accessible? ... yes
Checking GitLab App ... Finished
Checking GitLab subtasks ... Finished