Master failure: spec/lib/gitlab/gpg_spec.rb:145

Job #864932909 failed for e1d7aca7:

Failures:
  1) Gitlab::Gpg.using_tmp_keychain keeps track of created and removed keychains in counters
     Failure/Error: expect(created.get).to eq(initial_created + 1)
       expected: 14.0
            got: 13.0
       (compared using ==)
     # ./spec/lib/gitlab/gpg_spec.rb:153:in `block (4 levels) in <top (required)>'
     # ./lib/gitlab/gpg.rb:103:in `optimistic_using_tmp_keychain'
     # ./lib/gitlab/gpg.rb:82:in `block (2 levels) in using_tmp_keychain'
     # ./lib/gitlab/gpg.rb:81:in `synchronize'
     # ./lib/gitlab/gpg.rb:81:in `block in using_tmp_keychain'
     # ./lib/gitlab/gpg.rb:80:in `using_tmp_keychain'
     # ./spec/lib/gitlab/gpg_spec.rb:152:in `block (3 levels) in <top (required)>'
     # ./spec/spec_helper.rb:351:in `block (3 levels) in <top (required)>'
     # ./spec/support/sidekiq_middleware.rb:9:in `with_sidekiq_server_middleware'
     # ./spec/spec_helper.rb:342:in `block (2 levels) in <top (required)>'
     # ./spec/spec_helper.rb:338:in `block (3 levels) in <top (required)>'
     # ./spec/spec_helper.rb:338:in `block (2 levels) in <top (required)>'

Minimal repoduction:

bundle exec spring rspec -f d spec/services/git/branch_hooks_service_spec.rb:227 spec/services/metrics/dashboard/custom_dashboard_service_spec.rb:35 spec/lib/gitlab/gpg_spec.rb:155

1. spec/services/git/branch_hooks_service_spec.rb:227 calls Gpg.using_tmp_keychain somewhere which memoizes the class level instance variable :@tmp_keychains_created
2. spec/services/metrics/dashboard/custom_dashboard_service_spec.rb:35 destroys Prometheus DB files with the :prometheus annotation
3. spec/lib/gitlab/gpg_spec.rb:155 then tries to query a new Prometheus counter, which has no increments. The increments happen instead in the counter stored inside the memoized class instance variable.