Merge branch 'pushes-since-gc-redis' into 'master' 19600-artifacts-show-up-in-interface-as-expired-immediately-although-configured-as-1-month-or-4-weeks

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, 16 insertions, 0 deletions

diff --git a/app/models/project.rb b/app/models/project.rb
index 4017cabe9f0..f3f3ffbbd28 100644
--- a/app/models/project.rb
+++ b/app/models/project.rb
@@ -1288,8 +1288,24 @@ class Project < ActiveRecord::Base
     end
   end
 
+  def pushes_since_gc
+    Gitlab::Redis.with { |redis| redis.get(pushes_since_gc_redis_key).to_i }
+  end
+
+  def increment_pushes_since_gc
+    Gitlab::Redis.with { |redis| redis.incr(pushes_since_gc_redis_key) }
+  end
+
+  def reset_pushes_since_gc
+    Gitlab::Redis.with { |redis| redis.del(pushes_since_gc_redis_key) }
+  end
+
   private
 
+  def pushes_since_gc_redis_key
+    "projects/#{id}/pushes_since_gc"
+  end
+
   # Prevents the creation of project_feature record for every project
   def setup_project_feature
     build_project_feature unless project_feature