Support resetting of Prometheus metrics between test runs

Adding the :prometheus tag to an rspec test will clear out
memory-mapped files and reset the registry.

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/39968

1 files changed, 8 insertions, 0 deletions

diff --git a/lib/gitlab/metrics/prometheus.rb b/lib/gitlab/metrics/prometheus.rb
index d12ba0ec176..d41a855bff1 100644
--- a/lib/gitlab/metrics/prometheus.rb
+++ b/lib/gitlab/metrics/prometheus.rb
@@ -25,6 +25,14 @@ module Gitlab
           end
         end
 
+        def reset_registry!
+          clear_memoization(:registry)
+
+          REGISTRY_MUTEX.synchronize do
+            ::Prometheus::Client.reset!
+          end
+        end
+
         def registry
           strong_memoize(:registry) do
             REGISTRY_MUTEX.synchronize do