Merge branch 'sidekiq-api-metrics' into 'master'

Added API endpoint for Sidekiq Metrics.

## What does this MR do?

It adds an API endpoint to gather metrics about Sidekiq, it's jobs, queues, and processes.

## Why was this MR needed?

There was no API endpoint for Sidekiq information.

## What are the relevant issue numbers?

Fixes #7171

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- [x] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [x] API support added
- [x] Tests
  - [x] Added for this feature/bug
  - [x] All builds are passing

See merge request !4653

2 files changed, 91 insertions, 0 deletions

diff --git a/lib/api/api.rb b/lib/api/api.rb
index 6cd909f6115..51ddd0dbfc4 100644
--- a/lib/api/api.rb
+++ b/lib/api/api.rb
@@ -59,5 +59,6 @@ module API
     mount ::API::Licenses
     mount ::API::Subscriptions
     mount ::API::Gitignores
+    mount ::API::SidekiqMetrics
   end
 end
diff --git a/lib/api/sidekiq_metrics.rb b/lib/api/sidekiq_metrics.rb
new file mode 100644
index 00000000000..d3d6827dc54
--- /dev/null
+++ b/lib/api/sidekiq_metrics.rb
@@ -0,0 +1,90 @@
+require 'sidekiq/api'
+
+module API
+  class SidekiqMetrics < Grape::API
+    before { authenticated_as_admin! }
+
+    helpers do
+      def queue_metrics
+        Sidekiq::Queue.all.each_with_object({}) do |queue, hash|
+          hash[queue.name] = {
+            backlog: queue.size,
+            latency: queue.latency.to_i
+          }
+        end
+      end
+
+      def process_metrics
+        Sidekiq::ProcessSet.new.map do |process|
+          {
+            hostname:    process['hostname'],
+            pid:         process['pid'],
+            tag:         process['tag'],
+            started_at:  Time.at(process['started_at']),
+            queues:      process['queues'],
+            labels:      process['labels'],
+            concurrency: process['concurrency'],
+            busy:        process['busy']
+          }
+        end
+      end
+
+      def job_stats
+        stats = Sidekiq::Stats.new
+        {
+          processed: stats.processed,
+          failed: stats.failed,
+          enqueued: stats.enqueued
+        }
+      end
+    end
+
+    # Get Sidekiq Queue metrics
+    #
+    # Parameters:
+    #   None
+    #
+    # Example:
+    #   GET /sidekiq/queue_metrics
+    #
+    get 'sidekiq/queue_metrics' do
+      { queues: queue_metrics }
+    end
+
+    # Get Sidekiq Process metrics
+    #
+    # Parameters:
+    #   None
+    #
+    # Example:
+    #   GET /sidekiq/process_metrics
+    #
+    get 'sidekiq/process_metrics' do
+      { processes: process_metrics }
+    end
+
+    # Get Sidekiq Job statistics
+    #
+    # Parameters:
+    #   None
+    #
+    # Example:
+    #   GET /sidekiq/job_stats
+    #
+    get 'sidekiq/job_stats' do
+      { jobs: job_stats }
+    end
+
+    # Get Sidekiq Compound metrics. Includes all previous metrics
+    #
+    # Parameters:
+    #   None
+    #
+    # Example:
+    #   GET /sidekiq/compound_metrics
+    #
+    get 'sidekiq/compound_metrics' do
+      { queues: queue_metrics, processes: process_metrics, jobs: job_stats }
+    end
+  end
+end