Checking sidekiq fails with sidekiq cluster
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### Summary
On installation from source with sidekiq cluster the `bundle exec rake gitlab:check RAILS_ENV=production` check finds fault with more than one sidekiq process running. But with sidekiq cluster this is normal and correct.
### Steps to reproduce
1. Install gitlab-foss from source (version >=12.10; since then sidekiq cluster is the default according to https://gitlab.com/gitlab-org/gitlab-foss/-/blob/master/doc/install/installation.md#using-sidekiq-instead-of-sidekiq-cluster)
2. Start the gitlab services
3. Run `sudo -u git -H bundle exec rake gitlab:check RAILS_ENV=production SANITIZE=true`
### What is the current *bug* behavior?
The above `gitlab:check` command says:
```
Checking Sidekiq ...
Sidekiq: ... Running? ... yes
Number of Sidekiq processes ... 5
Try fixing it:
sudo service gitlab stop
sudo pkill -u git -f sidekiq
sleep 10 && sudo pkill -9 -u git -f sidekiq
sudo service gitlab start
Please fix the error above and rerun the checks.
Checking Sidekiq ... Finished
```
### What is the expected *correct* behavior?
The above `gitlab:check` command should say:
```
Checking Sidekiq ...
Sidekiq: ... Running? ... yes
Number of Sidekiq processes ... 5
Checking Sidekiq ... Finished
```
#### Results of GitLab environment info
<!-- Input any relevant GitLab environment information if needed. -->
<details>
<summary>Expand for output related to GitLab environment info</summary>
<pre>
System information
System:
Current User: git
Using RVM: no
Ruby Version: 2.7.2p137
Gem Version: 3.1.2
Bundler Version:2.1.4
Rake Version: 13.0.1
Redis Version: 6.0.9
Git Version: 2.29.2
Sidekiq Version:5.2.9
Go Version: go1.15.5 linux/amd64
GitLab information
Version: 13.7.0
Revision: 91da1dcc7a1
Directory: /opt/gitlab/gitlabhq-13.7
DB Adapter: PostgreSQL
DB Version: 12.5
URL: https://<host-only-reachable-from-inside-our-organization>
HTTP Clone URL: https://<host-only-reachable-from-inside-our-organization>/some-group/some-project.git
SSH Clone URL: git@<host-only-reachable-from-inside-our-organization>:some-group/some-project.git
Using LDAP: yes
Using Omniauth: no
GitLab Shell
Version: 13.15.0
Repository storage paths:
- default: /var/lib/gitlab/repositories
GitLab Shell path: /opt/gitlab/gitlab-shell
Git: /usr/bin/git
</pre>
</details>
#### Results of GitLab application Check
<!-- Input any relevant GitLab application check information if needed. -->
<details>
<summary>Expand for output related to the GitLab application check</summary>
<pre>
Checking GitLab subtasks ...
Checking GitLab Shell ...
GitLab Shell: ... GitLab Shell version >= 13.14.0 ? ... OK (13.15.0)
Running /opt/gitlab/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 ... 5
Try fixing it:
sudo service gitlab stop
sudo pkill -u git -f sidekiq
sleep 10 && sudo pkill -9 -u git -f sidekiq
sudo service gitlab start
Please fix the error above and rerun the checks.
Checking Sidekiq ... Finished
Checking Incoming Email ...
Incoming Email: ... Reply by email is disabled in config/gitlab.yml
Checking Incoming Email ... Finished
Checking LDAP ...
LDAP: ... Server: ldapmain
LDAP authentication... Success
LDAP users with access to your GitLab server (only showing the first 100 results)
User output sanitized. Found 22 users of 100 limit.
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
Projects have namespace: ...
11/5 ... yes
... (many more; all with a gren "yes")
Redis version >= 4.0.0? ... yes
Ruby version >= 2.7.2 ? ... yes (2.7.2)
Git version >= 2.29.0 ? ... yes (2.29.2)
Git user has default SSH configuration? ... yes
Active users: ... 108
Is authorized keys file accessible? ... yes
GitLab configured to store new projects in hashed storage? ... yes
All projects are in hashed storage? ... yes
Checking GitLab App ... Finished
Checking GitLab subtasks ... Finished
</pre>
</details>
### Possible fixes
https://gitlab.com/gitlab-org/gitlab-foss/-/blob/master/lib/system_check/sidekiq_check.rb#L33
issue