[DRE-maint] Bug#968626: gitlab: Error 500 during CI artifacts upload from gitlab-runner

[Maximilian Stein]

Package: gitlab
Version: 13.2.3-2+fto10+1
Severity: normal

Dear Maintainer,

Since the upgrade to above mentioned version, artifact uploads from
gitlab runners fail with an error 500.

Snippet from the job log:

---
Uploading artifacts...
time="2020-08-18T19:42:06+02:00" level=error msg="Docker executor: prebuilt image will be loaded from /var/lib/gitlab-runner."
Runtime platform                                    arch=amd64 os=linux pid=32578 revision=13.0.1 version=13.0.1
debian/pkg/*: found 6 matching files
WARNING: Uploading artifacts to coordinator... failed  id=3633 responseStatus=500 Internal Server Error status=500 Internal Server Error token=00000000
WARNING: Retrying...                                context=artifacts-uploader error=invalid argument
WARNING: Uploading artifacts to coordinator... failed  id=3633 responseStatus=500 Internal Server Error status=500 Internal Server Error token=00000000
WARNING: Retrying...                                context=artifacts-uploader error=invalid argument
WARNING: Uploading artifacts to coordinator... failed  id=3633 responseStatus=500 Internal Server Error status=500 Internal Server Error token=00000000
---


In the production.log I found the following stack trace:

---
Started POST "/api/v4/jobs/3633/artifacts?artifact_format=zip&artifact_type=archive&expire_in=12+hours" for 1.2.3.4 at 2020-08-18 19:42:06 +0200

NoMethodError (undefined method `empty?' for 201:Integer):

lib/gitlab/middleware/read_only/controller.rb:51:in `call'
lib/gitlab/middleware/read_only.rb:18:in `call'
lib/gitlab/middleware/same_site_cookies.rb:27:in `call'
lib/gitlab/middleware/basic_health_check.rb:25:in `call'
lib/gitlab/middleware/handle_ip_spoof_attack_error.rb:25:in `call'
lib/gitlab/middleware/request_context.rb:23:in `call'
config/initializers/fix_local_cache_middleware.rb:9:in `call'
lib/gitlab/metrics/requests_rack_middleware.rb:60:in `call'
lib/gitlab/middleware/release_env.rb:12:in `call' 
---

Unfortunately, the call stack ends here. As far as I can tell, this is
only middelware code, and I was not able to easily find the
problematic usage of `empty?` anywhere nearby this code. Is there a
way to increase the number of lines in the stack trace?

Although the CI jobs fails with this error, the artifacts themselves
are still uploaded successfully and can be viewed/downloaded in the
gitlab UI. So, this only seems to be a minor problem in the artifact
logic.

The particular runner instance was at version 11.2.0+dfsg-2 and worked
with the previously installed gitlab version (13.1.6-1+fto10+1).
Upgrading the runner to version 13.0.1+dfsg-1 did not change the
situation.

Thank you very much!

Best,
Maximilian