Add optional MongoSilencer plugin

.rubocop.yml

@@ -8,7 +8,14 @@ Metrics:
 Metrics/LineLength:
   Max: 512
 
+Style/BracesAroundHashParameters:
+  Enabled: false
+
 Style/Documentation:
   Enabled: false
 
+Style/GlobalVars:
+  Exclude:
+    - spec/**/*
+
 inherit_from: .rubocop_todo.yml

CHANGELOG.md

@@ -1,6 +1,7 @@
 ### 3.0.1
 
 * Your contribution here.
+* [#89](https://github.com/collectiveidea/delayed_job_mongoid/pull/89): Add MongoSilencer plugin to silence Delayed Job polling - [johnnyshields](https://github.com/johnnyshields).
 * [#88](https://github.com/collectiveidea/delayed_job_mongoid/pull/88): Extract out mixin to enable better backend customization - [johnnyshields](https://github.com/johnnyshields).
 
 ### 3.0.0

README.md

@@ -38,6 +38,24 @@ That's it. Use [delayed_job](http://github.com/collectiveidea/delayed_job) as no
 
 ## Advanced Usage
 
+### Silencing Noisy Logging
+
+By default, the Mongo Ruby Driver will print log lines every
+5 seconds as Delayed Job polls your database. Use the following
+plugin to silence logs which happen while polling (except `error`
+level) and only log operations which happen during job execution.
+
+```ruby
+# in initializers/delayed_job.rb
+
+require 'delayed/plugins/mongo_silencer'
+Delayed::Worker.plugins << Delayed::Plugins::MongoSilencer
+```
+
+To ensure thread safety, this plugin requires your `Mongo::Logger.logger`
+to be an instance of `ActiveSupport::Logger` class. It will ignore instances
+of the Ruby standard library `Logger` class.
+
 ### Customizing Job Class
 
 Delayed Job allows specifying a custom backend class for jobs.

lib/delayed/plugins/mongo_silencer.rb

@@ -0,0 +1,49 @@
+require 'mongo'
+require 'delayed/plugin'
+
+module Delayed
+  module Plugins
+    # Silences the Mongo logger except when performing jobs.
+    # Requires the Mongoid/Mongo loggers to be instances of ActiveSupport::Logger.
+    class MongoSilencer < Delayed::Plugin
+      callbacks do |lifecycle|
+        lifecycle.before(:execute) do |*_args|
+          store_log_level
+          silence!
+        end
+
+        # As of Delayed Job 4.10, the :perform hook includes the
+        # operations for job deletion and job errors, so these will
+        # still appear in the log.
+        lifecycle.around(:perform) do |*_args, &block|
+          begin
+            unsilence!
+            block.call
+          ensure
+            silence!
+          end
+        end
+      end
+
+      class << self
+        def store_log_level
+          @mongo_log_level = Mongo::Logger.logger.level if mongo_logger?
+        end
+
+        def silence!
+          Mongo::Logger.logger.local_level = Logger::WARN if @mongo_log_level && mongo_logger?
+        end
+
+        def unsilence!
+          Mongo::Logger.logger.local_level = @mongo_log_level if @mongo_log_level && mongo_logger?
+        end
+
+        private
+
+        def mongo_logger?
+          Mongo::Logger.logger && Mongo::Logger.logger.respond_to?(:local_level)
+        end
+      end
+    end
+  end
+end

spec/delayed_job_mongoid_spec.rb

@@ -1,6 +1,4 @@
-require 'helper'
-require 'models/story'
-require 'models/story_wrapper_job'
+require 'spec_helper'
 
 describe Delayed::Backend::Mongoid::Job do
   it_behaves_like 'a delayed_job backend'

spec/models/story_wrapper_job.rb

@@ -1,4 +1,7 @@
 class StoryWrapperJob < SimpleJob
+  # TODO: remove this line when https://github.com/collectiveidea/delayed_job/pull/1166 is merged
+  @@runs = 0
+
   def initialize
     @story = Story.create!(text: 'My great story')
     @story_again = @story

spec/mongo_silencer_spec.rb

@@ -0,0 +1,63 @@
+require 'spec_helper'
+
+describe Delayed::Plugins::MongoSilencer do
+  let(:mongoid_io) { StringIO.new }
+  let(:mongoid_logger) { ActiveSupport::Logger.new(mongoid_io) }
+  let(:mongo_io) { StringIO.new }
+  let(:mongo_logger) { ActiveSupport::Logger.new(mongo_io) }
+  let(:run_worker) do
+    worker = Delayed::Worker.new
+    thread = Thread.new { worker.start }
+    sleep(0.5)
+    worker.stop
+    thread.join
+  end
+
+  before do
+    Delayed::Job.create(payload_object: StoryWrapperJob.new)
+    Mongoid.logger = mongoid_logger
+    Mongo::Logger.logger = mongo_logger
+    Delayed::Worker.sleep_delay = 0.1
+  end
+
+  after do
+    Delayed::Worker.reset
+    Delayed::Worker.plugins = []
+    Mongoid.logger = $mongoid_logger
+    Mongo::Logger.logger = $mongo_logger
+  end
+
+  context 'when plugin is set' do
+    before do
+      Delayed::Worker.plugins << described_class
+    end
+
+    context 'when using ActiveSupport::Logger' do
+      it do
+        run_worker
+        expect(mongoid_io.string.lines.size).to eq 0
+        expect(mongo_io.string.lines.any? { |l| l.include?('"find"=>"stories"') }).to eq true
+        expect(mongo_io.string.lines.any? { |l| l.include?('"findAndModify"=>"delayed_backend_mongoid_jobs"') }).to eq false
+      end
+    end
+
+    context 'when Mongo logger is a Logger' do
+      let(:mongo_logger) { Logger.new(mongo_io) }
+
+      it do
+        run_worker
+        expect(mongo_io.string.lines.any? { |l| l.include?('"find"=>"stories"') }).to eq true
+        expect(mongo_io.string.lines.any? { |l| l.include?('"findAndModify"=>"delayed_backend_mongoid_jobs"') }).to eq true
+      end
+    end
+  end
+
+  context 'when plugin is not set' do
+    it do
+      run_worker
+      expect(mongoid_io.string.lines.size).to eq 0
+      expect(mongo_io.string.lines.any? { |l| l.include?('"find"=>"stories"') }).to eq true
+      expect(mongo_io.string.lines.any? { |l| l.include?('"findAndModify"=>"delayed_backend_mongoid_jobs"') }).to eq true
+    end
+  end
+end

spec/helper.rb → spec/spec_helper.rb

@@ -11,7 +11,13 @@
 
 require 'rspec'
 require 'delayed_job_mongoid'
+require 'delayed/plugins/mongo_silencer'
 require 'delayed/backend/shared_spec'
+require 'models/story'
+require 'models/story_wrapper_job'
+
+$mongoid_logger = Mongoid.logger
+$mongo_logger = Mongo::Logger.logger
 
 RSpec.configure do |config|
   config.expect_with(:rspec) do |c|