Merge branch 'redis-connection-pool' into 'master'

Redis connection pool

Split from https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/3232

Having an easily accessible Redis connection pool allows us to do more
cool stuff with Redis in GitLab (instead of having to go through e.g.
the Rails cache).

See merge request !3521

10 files changed, 77 insertions, 54 deletions

diff --git a/Gemfile b/Gemfile
index 0279b4ac47e..46431158fb5 100644
--- a/Gemfile
+++ b/Gemfile
@@ -149,6 +149,10 @@ gem 'version_sorter', '~> 2.0.0'
 # Cache
 gem "redis-rails", '~> 4.0.0'
 
+# Redis
+gem 'redis', '~> 3.2'
+gem 'connection_pool', '~> 2.0'
+
 # Campfire integration
 gem 'tinder', '~> 1.10.0'
 
@@ -229,7 +233,6 @@ group :metrics do
   gem 'allocations', '~> 1.0', require: false, platform: :mri
   gem 'method_source', '~> 0.8', require: false
   gem 'influxdb', '~> 0.2', require: false
-  gem 'connection_pool', '~> 2.0', require: false
 end
 
 group :development do
diff --git a/Gemfile.lock b/Gemfile.lock
index 1ba8d748db1..a30706a4318 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -999,6 +999,7 @@ DEPENDENCIES
   rdoc (~> 3.6)
   recaptcha
   redcarpet (~> 3.3.3)
+  redis (~> 3.2)
   redis-namespace
   redis-rails (~> 4.0.0)
   request_store (~> 1.3.0)
diff --git a/config/application.rb b/config/application.rb
index 5a0ac70aa2a..2e2ed48db07 100644
--- a/config/application.rb
+++ b/config/application.rb
@@ -4,11 +4,9 @@ require 'rails/all'
 require 'devise'
 I18n.config.enforce_available_locales = false
 Bundler.require(:default, Rails.env)
-require_relative '../lib/gitlab/redis_config'
+require_relative '../lib/gitlab/redis'
 
 module Gitlab
-  REDIS_CACHE_NAMESPACE = 'cache:gitlab'
-
   class Application < Rails::Application
     # Settings in config/environments/* take precedence over those specified here.
     # Application configuration should go into files in config/initializers
@@ -69,8 +67,8 @@ module Gitlab
       end
     end
 
-    redis_config_hash = Gitlab::RedisConfig.redis_store_options
-    redis_config_hash[:namespace] = REDIS_CACHE_NAMESPACE
+    redis_config_hash = Gitlab::Redis.redis_store_options
+    redis_config_hash[:namespace] = Gitlab::Redis::CACHE_NAMESPACE
     redis_config_hash[:expires_in] = 2.weeks # Cache should not grow forever
     config.cache_store = :redis_store, redis_config_hash
 
diff --git a/config/initializers/session_store.rb b/config/initializers/session_store.rb
index 3da5d46be92..70285255877 100644
--- a/config/initializers/session_store.rb
+++ b/config/initializers/session_store.rb
@@ -13,7 +13,7 @@ end
 if Rails.env.test?
   Gitlab::Application.config.session_store :cookie_store, key: "_gitlab_session"
 else
-  redis_config = Gitlab::RedisConfig.redis_store_options
+  redis_config = Gitlab::Redis.redis_store_options
   redis_config[:namespace] = 'session:gitlab'
   
   Gitlab::Application.config.session_store(
diff --git a/config/initializers/sidekiq.rb b/config/initializers/sidekiq.rb
index cc83137745a..9182d929809 100644
--- a/config/initializers/sidekiq.rb
+++ b/config/initializers/sidekiq.rb
@@ -2,7 +2,7 @@ SIDEKIQ_REDIS_NAMESPACE = 'resque:gitlab'
 
 Sidekiq.configure_server do |config|
   config.redis = {
-    url: Gitlab::RedisConfig.url,
+    url: Gitlab::Redis.url,
     namespace: SIDEKIQ_REDIS_NAMESPACE
   }
 
@@ -29,7 +29,7 @@ end
 
 Sidekiq.configure_client do |config|
   config.redis = {
-    url: Gitlab::RedisConfig.url,
+    url: Gitlab::Redis.url,
     namespace: SIDEKIQ_REDIS_NAMESPACE
   }
 end
diff --git a/config/mail_room.yml b/config/mail_room.yml
index 60257329f3e..761a32adb9e 100644
--- a/config/mail_room.yml
+++ b/config/mail_room.yml
@@ -2,7 +2,7 @@
 <%
 require "yaml"
 require "json"
-require_relative "lib/gitlab/redis_config"
+require_relative "lib/gitlab/redis"
 
 rails_env = ENV["RAILS_ENV"] || ENV["RACK_ENV"] || "development"
 
@@ -18,7 +18,7 @@ if File.exists?(config_file)
   config['mailbox']    = "inbox"  if config['mailbox'].nil?
 
   if config['enabled'] && config['address']
-    redis_url = Gitlab::RedisConfig.new(rails_env).url
+    redis_url = Gitlab::Redis.new(rails_env).url
     %>
     -
       :host: <%= config['host'].to_json %>
diff --git a/lib/gitlab/exclusive_lease.rb b/lib/gitlab/exclusive_lease.rb
index c73eca832d7..c2260a5f7ac 100644
--- a/lib/gitlab/exclusive_lease.rb
+++ b/lib/gitlab/exclusive_lease.rb
@@ -43,7 +43,9 @@ module Gitlab
     # false if the lease is already taken.
     def try_obtain
       # Performing a single SET is atomic
-      !!redis.set(redis_key, '1', nx: true, ex: @timeout)
+      Gitlab::Redis.with do |redis|
+        !!redis.set(redis_key, '1', nx: true, ex: @timeout)
+      end
     end
 
     # No #cancel method. See comments above!
diff --git a/lib/gitlab/redis.rb b/lib/gitlab/redis.rb
new file mode 100644
index 00000000000..319447669dc
--- /dev/null
+++ b/lib/gitlab/redis.rb
@@ -0,0 +1,48 @@
+module Gitlab
+  class Redis
+    CACHE_NAMESPACE = 'cache:gitlab'
+
+    attr_reader :url
+
+    # To be thread-safe we must be careful when writing the class instance
+    # variables @url and @pool. Because @pool depends on @url we need two
+    # mutexes to prevent deadlock.
+    URL_MUTEX = Mutex.new
+    POOL_MUTEX = Mutex.new
+    private_constant :URL_MUTEX, :POOL_MUTEX
+
+    def self.url
+      @url || URL_MUTEX.synchronize { @url = new.url }
+    end
+
+    def self.with
+      if @pool.nil?
+        POOL_MUTEX.synchronize do
+          @pool = ConnectionPool.new { ::Redis.new(url: url) }
+        end
+      end
+      @pool.with { |redis| yield redis }
+    end
+    
+    def self.redis_store_options
+      url = new.url
+      redis_config_hash = ::Redis::Store::Factory.extract_host_options_from_uri(url)
+      # Redis::Store does not handle Unix sockets well, so let's do it for them
+      redis_uri = URI.parse(url)
+      if redis_uri.scheme == 'unix'
+        redis_config_hash[:path] = redis_uri.path
+      end
+      redis_config_hash
+    end
+
+    def initialize(rails_env=nil)
+      rails_env ||= Rails.env
+      config_file = File.expand_path('../../../config/resque.yml', __FILE__)
+  
+      @url = "redis://localhost:6379"
+      if File.exists?(config_file)
+        @url =YAML.load_file(config_file)[rails_env]
+      end
+    end
+  end
+end
diff --git a/lib/gitlab/redis_config.rb b/lib/gitlab/redis_config.rb
deleted file mode 100644
index 4949c6db539..00000000000
--- a/lib/gitlab/redis_config.rb
+++ /dev/null
@@ -1,30 +0,0 @@
-module Gitlab
-  class RedisConfig
-    attr_reader :url
-
-    def self.url
-      new.url
-    end
-    
-    def self.redis_store_options
-      url = new.url
-      redis_config_hash = Redis::Store::Factory.extract_host_options_from_uri(url)
-      # Redis::Store does not handle Unix sockets well, so let's do it for them
-      redis_uri = URI.parse(url)
-      if redis_uri.scheme == 'unix'
-        redis_config_hash[:path] = redis_uri.path
-      end
-      redis_config_hash
-    end
-
-    def initialize(rails_env=nil)
-      rails_env ||= Rails.env
-      config_file = File.expand_path('../../../config/resque.yml', __FILE__)
-  
-      @url = "redis://localhost:6379"
-      if File.exists?(config_file)
-        @url =YAML.load_file(config_file)[rails_env]
-      end
-    end
-  end
-end
diff --git a/lib/tasks/cache.rake b/lib/tasks/cache.rake
index 51e746ef923..2214f855200 100644
--- a/lib/tasks/cache.rake
+++ b/lib/tasks/cache.rake
@@ -4,18 +4,19 @@ namespace :cache do
 
   desc "GitLab | Clear redis cache"
   task :clear => :environment do
-    redis = Redis.new(url: Gitlab::RedisConfig.url)
-    cursor = REDIS_SCAN_START_STOP
-    loop do
-      cursor, keys = redis.scan(
-        cursor,
-        match: "#{Gitlab::REDIS_CACHE_NAMESPACE}*", 
-        count: CLEAR_BATCH_SIZE
-      )
-
-      redis.del(*keys) if keys.any?
-
-      break if cursor == REDIS_SCAN_START_STOP
+    Gitlab::Redis.with do |redis|
+      cursor = REDIS_SCAN_START_STOP
+      loop do
+        cursor, keys = redis.scan(
+          cursor,
+          match: "#{Gitlab::Redis::CACHE_NAMESPACE}*", 
+          count: CLEAR_BATCH_SIZE
+        )
+  
+        redis.del(*keys) if keys.any?
+  
+        break if cursor == REDIS_SCAN_START_STOP
+      end
     end
   end
 end