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

5 files changed, 284 insertions, 0 deletions

diff --git a/CHANGELOG b/CHANGELOG
index 620a7eea378..c0bfe8db076 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -46,6 +46,7 @@ v 8.9.0 (unreleased)
   - Fixed alignment of download dropdown in merge requests
   - Upgrade to jQuery 2
   - Adds selected branch name to the dropdown toggle
+  - Add API endpoint for Sidekiq Metrics !4653
   - Use Knapsack to evenly distribute tests across multiple nodes
   - Add `sha` parameter to MR merge API, to ensure only reviewed changes are merged
   - Don't allow MRs to be merged when commits were added since the last review / page load
diff --git a/doc/api/sidekiq_metrics.md b/doc/api/sidekiq_metrics.md
new file mode 100644
index 00000000000..ebd131c94ca
--- /dev/null
+++ b/doc/api/sidekiq_metrics.md
@@ -0,0 +1,152 @@
+# Sidekiq Metrics
+
+>**Note:** This endpoint is only available on GitLab 8.9 and above.
+
+This API endpoint allows you to retrieve some information about the current state
+of Sidekiq, its jobs, queues, and processes.
+
+## Get the current Queue Metrics
+
+List information about all the registered queues, their backlog and their
+latency.
+
+```
+GET /sidekiq/queue_metrics
+```
+
+```bash
+curl -H "PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK" https://gitlab.example.com/api/v3/sidekiq/queue_metrics
+```
+
+Example response:
+
+```json
+{
+  "queues": {
+    "default": {
+      "backlog": 0,
+      "latency": 0
+    }
+  }
+}
+```
+
+## Get the current Process Metrics
+
+List information about all the Sidekiq workers registered to process your queues.
+
+```
+GET /sidekiq/process_metrics
+```
+
+```bash
+curl -H "PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK" https://gitlab.example.com/api/v3/sidekiq/process_metrics
+```
+
+Example response:
+
+```json
+{
+  "processes": [
+    {
+      "hostname": "gitlab.example.com",
+      "pid": 5649,
+      "tag": "gitlab",
+      "started_at": "2016-06-14T10:45:07.159-05:00",
+      "queues": [
+        "post_receive",
+        "mailers",
+        "archive_repo",
+        "system_hook",
+        "project_web_hook",
+        "gitlab_shell",
+        "incoming_email",
+        "runner",
+        "common",
+        "default"
+      ],
+      "labels": [],
+      "concurrency": 25,
+      "busy": 0
+    }
+  ]
+}
+```
+
+## Get the current Job Statistics
+
+List information about the jobs that Sidekiq has performed.
+
+```
+GET /sidekiq/job_stats
+```
+
+```bash
+curl -H "PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK" https://gitlab.example.com/api/v3/sidekiq/job_stats
+```
+
+Example response:
+
+```json
+{
+  "jobs": {
+    "processed": 2,
+    "failed": 0,
+    "enqueued": 0
+  }
+}
+```
+
+## Get a compound response of all the previously mentioned metrics
+
+List all the currently available information about Sidekiq.
+
+```
+GET /sidekiq/compound_metrics
+```
+
+```bash
+curl -H "PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK" https://gitlab.example.com/api/v3/sidekiq/compound_metrics
+```
+
+Example response:
+
+```json
+{
+  "queues": {
+    "default": {
+      "backlog": 0,
+      "latency": 0
+    }
+  },
+  "processes": [
+    {
+      "hostname": "gitlab.example.com",
+      "pid": 5649,
+      "tag": "gitlab",
+      "started_at": "2016-06-14T10:45:07.159-05:00",
+      "queues": [
+        "post_receive",
+        "mailers",
+        "archive_repo",
+        "system_hook",
+        "project_web_hook",
+        "gitlab_shell",
+        "incoming_email",
+        "runner",
+        "common",
+        "default"
+      ],
+      "labels": [],
+      "concurrency": 25,
+      "busy": 0
+    }
+  ],
+  "jobs": {
+    "processed": 2,
+    "failed": 0,
+    "enqueued": 0
+  }
+}
+```
+
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
diff --git a/spec/requests/api/sidekiq_metrics_spec.rb b/spec/requests/api/sidekiq_metrics_spec.rb
new file mode 100644
index 00000000000..41cbf0c6669
--- /dev/null
+++ b/spec/requests/api/sidekiq_metrics_spec.rb
@@ -0,0 +1,40 @@
+require 'spec_helper'
+
+describe API::SidekiqMetrics, api: true do
+  include ApiHelpers
+
+  let(:admin) { create(:user, :admin) }
+
+  describe 'GET sidekiq/*' do
+    it 'defines the `queue_metrics` endpoint' do
+      get api('/sidekiq/queue_metrics', admin)
+
+      expect(response.status).to eq(200)
+      expect(json_response).to be_a Hash
+    end
+
+    it 'defines the `process_metrics` endpoint' do
+      get api('/sidekiq/process_metrics', admin)
+
+      expect(response.status).to eq(200)
+      expect(json_response['processes']).to be_an Array
+    end
+
+    it 'defines the `job_stats` endpoint' do
+      get api('/sidekiq/job_stats', admin)
+
+      expect(response.status).to eq(200)
+      expect(json_response).to be_a Hash
+    end
+
+    it 'defines the `compound_metrics` endpoint' do
+      get api('/sidekiq/compound_metrics', admin)
+
+      expect(response.status).to eq(200)
+      expect(json_response).to be_a Hash
+      expect(json_response['queues']).to be_a Hash
+      expect(json_response['processes']).to be_an Array
+      expect(json_response['jobs']).to be_a Hash
+    end
+  end
+end