Merge branch 'pushes-since-gc-redis' into 'master'

Move pushes_since_gc to Redis

## What does this MR do?

This moves tracking of the pushes since the last Git GC to Redis to reduce DB load.

## Are there points in the code the reviewer needs to double check?

Styling mostly.

## Why was this MR needed?

Updating this column can lead to a lot of writes which in turn puts a lot of load on table vacuuming. For example, in the last hour alone we had 5067 UPDATEs for this column (per InfluxDB):

```
> select count(increment_pushes_since_gc_call_count) from sidekiq_transactions where time > now() - 1h;
name: sidekiq_transactions
--------------------------
time                    count
1473780996567714622     5067
```

## What are the relevant issue numbers?

https://gitlab.com/gitlab-org/gitlab-ce/issues/22125

See merge request !6326

1 files changed, 3 insertions, 9 deletions

diff --git a/app/services/projects/housekeeping_service.rb b/app/services/projects/housekeeping_service.rb
index 29b3981f49f..c3dfc8cfbe8 100644
--- a/app/services/projects/housekeeping_service.rb
+++ b/app/services/projects/housekeeping_service.rb
@@ -30,10 +30,8 @@ module Projects
     end
 
     def increment!
-      if Gitlab::ExclusiveLease.new("project_housekeeping:increment!:#{@project.id}", timeout: 60).try_obtain
-        Gitlab::Metrics.measure(:increment_pushes_since_gc) do
-          update_pushes_since_gc(@project.pushes_since_gc + 1)
-        end
+      Gitlab::Metrics.measure(:increment_pushes_since_gc) do
+        @project.increment_pushes_since_gc
       end
     end
 
@@ -43,14 +41,10 @@ module Projects
       GitGarbageCollectWorker.perform_async(@project.id)
     ensure
       Gitlab::Metrics.measure(:reset_pushes_since_gc) do
-        update_pushes_since_gc(0)
+        @project.reset_pushes_since_gc
       end
     end
 
-    def update_pushes_since_gc(new_value)
-      @project.update_column(:pushes_since_gc, new_value)
-    end
-
     def try_obtain_lease
       Gitlab::Metrics.measure(:obtain_housekeeping_lease) do
         lease = ::Gitlab::ExclusiveLease.new("project_housekeeping:#{@project.id}", timeout: LEASE_TIMEOUT)