From 4aab89b288b417cf0c2e6303c9ca59ea7efb5bd8 Mon Sep 17 00:00:00 2001
From: brainopia <brainopia@evilmartians.com>
Date: Thu, 24 Jan 2013 16:03:28 +0400
Subject: [PATCH] Add global mode

---
 README.md                                     |  8 +-
 .../{limit_fetch => extensions}/queue.rb      |  8 +-
 lib/sidekiq/limit_fetch.rb                    | 58 +++---------
 lib/sidekiq/limit_fetch/global/selector.rb    | 92 +++++++++++++++++++
 lib/sidekiq/limit_fetch/global/semaphore.rb   | 38 ++++++++
 lib/sidekiq/limit_fetch/local/selector.rb     | 19 ++++
 lib/sidekiq/limit_fetch/local/semaphore.rb    | 39 ++++++++
 lib/sidekiq/limit_fetch/queues.rb             | 57 ++++++++++++
 lib/sidekiq/limit_fetch/semaphore.rb          | 36 --------
 lib/sidekiq/limit_fetch/unit_of_work.rb       | 22 ++---
 spec/limit_fetch_spec.rb                      | 81 ----------------
 spec/sidekiq/extensions/queue_spec.rb         | 85 +++++++++++++++++
 spec/sidekiq/limit_fetch/queue_spec.rb        | 72 ---------------
 spec/sidekiq/limit_fetch/queues_spec.rb       | 75 +++++++++++++++
 spec/sidekiq/limit_fetch/semaphore_spec.rb    | 68 ++++++++++++++
 spec/sidekiq/limit_fetch_spec.rb              | 47 ++++++++++
 spec/spec_helper.rb                           | 12 +++
 17 files changed, 566 insertions(+), 251 deletions(-)
 rename lib/sidekiq/{limit_fetch => extensions}/queue.rb (64%)
 create mode 100644 lib/sidekiq/limit_fetch/global/selector.rb
 create mode 100644 lib/sidekiq/limit_fetch/global/semaphore.rb
 create mode 100644 lib/sidekiq/limit_fetch/local/selector.rb
 create mode 100644 lib/sidekiq/limit_fetch/local/semaphore.rb
 create mode 100644 lib/sidekiq/limit_fetch/queues.rb
 delete mode 100644 lib/sidekiq/limit_fetch/semaphore.rb
 delete mode 100644 spec/limit_fetch_spec.rb
 create mode 100644 spec/sidekiq/extensions/queue_spec.rb
 delete mode 100644 spec/sidekiq/limit_fetch/queue_spec.rb
 create mode 100644 spec/sidekiq/limit_fetch/queues_spec.rb
 create mode 100644 spec/sidekiq/limit_fetch/semaphore_spec.rb
 create mode 100644 spec/sidekiq/limit_fetch_spec.rb

diff --git a/README.md b/README.md
index 4794b39..87715f5 100644
--- a/README.md
+++ b/README.md
@@ -21,7 +21,7 @@ Specify limits which you want to place on queues inside sidekiq.yml:
 
 Or set it dynamically in your code:
 ```ruby
-  Sidekiq::Queue.new('queue_name1').limit = 5
+  Sidekiq::Queue['queue_name1'].limit = 5
   Sidekiq::Queue['queue_name2'].limit = 10
 ```
 
@@ -43,7 +43,11 @@ will be preserved.
 
 Limits are applied per process. In case you have several worker
 processes and want to have global locks between them, you'll need to
-wait just a bit more since support for global locks is underway.
+enable global mode by setting global option, eg:
+
+```yaml
+:global: true
+```
 
 Sponsored by [Evil Martians].
 [Evil Martians]: http://evilmartians.com/
diff --git a/lib/sidekiq/limit_fetch/queue.rb b/lib/sidekiq/extensions/queue.rb
similarity index 64%
rename from lib/sidekiq/limit_fetch/queue.rb
rename to lib/sidekiq/extensions/queue.rb
index dd44895..0452002 100644
--- a/lib/sidekiq/limit_fetch/queue.rb
+++ b/lib/sidekiq/extensions/queue.rb
@@ -8,12 +8,12 @@ module Sidekiq
       :pause,   :continue,
       :busy
 
-    def full_name
-      @rname
+    def lock
+      @lock ||= mode::Semaphore.new name
     end
 
-    def lock
-      @lock ||= LimitFetch::Semaphore.new
+    def mode
+      Sidekiq.options[:global] ? LimitFetch::Global : LimitFetch::Local
     end
   end
 end
diff --git a/lib/sidekiq/limit_fetch.rb b/lib/sidekiq/limit_fetch.rb
index 281b5be..5c7c69c 100644
--- a/lib/sidekiq/limit_fetch.rb
+++ b/lib/sidekiq/limit_fetch.rb
@@ -2,10 +2,14 @@ require 'sidekiq'
 require 'sidekiq/fetch'
 
 class Sidekiq::LimitFetch
-  require_relative 'limit_fetch/semaphore'
   require_relative 'limit_fetch/unit_of_work'
   require_relative 'limit_fetch/singleton'
-  require_relative 'limit_fetch/queue'
+  require_relative 'limit_fetch/queues'
+  require_relative 'limit_fetch/local/semaphore'
+  require_relative 'limit_fetch/local/selector'
+  require_relative 'limit_fetch/global/semaphore'
+  require_relative 'limit_fetch/global/selector'
+  require_relative 'extensions/queue'
 
   Sidekiq.options[:fetch] = self
 
@@ -14,55 +18,23 @@ class Sidekiq::LimitFetch
   end
 
   def initialize(options)
-    prepare_queues options
-    options[:strict] ? define_strict_queues : define_weighted_queues
-  end
-
-  def available_queues
-    fetch_queues.select(&:acquire)
+    @queues = Queues.new options
   end
 
   def retrieve_work
-    queues = available_queues
-
-    if queues.empty?
-      sleep Sidekiq::Fetcher::TIMEOUT
-      return
-    end
-
-    queue_name, message = Sidekiq.redis do |it|
-      it.brpop *queues.map(&:full_name), Sidekiq::Fetcher::TIMEOUT
-    end
-
-    if message
-      queue = queues.delete queues.find {|it| it.full_name == queue_name }
-      UnitOfWork.new queue, message
-    end
-  ensure
-    queues.each(&:release) if queues
+    queue, message = fetch_message
+    UnitOfWork.new queue, message if message
   end
 
   private
 
-  def prepare_queues(options)
-    limits = options[:limits] || {}
-    @queues = options[:queues].map do |name|
-      Sidekiq::Queue.new(name).tap do |it|
-        it.limit = limits[name] if limits[name]
-      end
-    end
+  def fetch_message
+    queue, _ = redis_blpop *@queues.acquire, Sidekiq::Fetcher::TIMEOUT
+  ensure
+    @queues.release_except queue
   end
 
-  def define_strict_queues
-    @queues.uniq!
-    def fetch_queues
-      @queues
-    end
-  end
-
-  def define_weighted_queues
-    def fetch_queues
-      @queues.shuffle.uniq
-    end
+  def redis_blpop(*args)
+    Sidekiq.redis {|it| it.blpop *args }
   end
 end
diff --git a/lib/sidekiq/limit_fetch/global/selector.rb b/lib/sidekiq/limit_fetch/global/selector.rb
new file mode 100644
index 0000000..6ade2f9
--- /dev/null
+++ b/lib/sidekiq/limit_fetch/global/selector.rb
@@ -0,0 +1,92 @@
+module Sidekiq::LimitFetch::Global
+  module Selector
+    extend self
+
+    def acquire(queues)
+      redis_eval :acquire, [namespace, uuid, queues]
+    end
+
+    def release(queues)
+      redis_eval :release, [namespace, uuid, queues]
+    end
+
+    private
+
+    def namespace
+      @namespace ||= begin
+        namespace = Sidekiq.options[:namespace]
+        namespace + ':' if namespace
+      end
+    end
+
+    def uuid
+      @uuid ||= SecureRandom.uuid
+    end
+
+    def redis_eval(script_name, args)
+      Sidekiq.redis do |it|
+        begin
+          it.evalsha send("redis_#{script_name}_sha"), argv: args
+        rescue Redis::CommandError => error
+          raise unless error.message.include? 'NOSCRIPT'
+          it.eval send("redis_#{script_name}_script"), argv: args
+        end
+      end
+    end
+
+    def redis_acquire_sha
+      @acquire_sha ||= Digest::SHA1.hexdigest redis_acquire_script
+    end
+
+    def redis_release_sha
+      @release_sha ||= Digest::SHA1.hexdigest redis_release_script
+    end
+
+    def redis_acquire_script
+      <<-LUA
+        local namespace   = table.remove(ARGV, 1)..'limit_fetch:'
+        local worker_name = table.remove(ARGV, 1)
+        local queues      = ARGV
+        local available   = {}
+
+        for _, queue in ipairs(queues) do
+          local busy_key    = namespace..'busy:'..queue
+          local pause_key   = namespace..'pause:'..queue
+          local paused      = redis.call('get', pause_key)
+
+          if not paused then
+            local limit_key   = namespace..'limit:'..queue
+            local queue_limit = tonumber(redis.call('get', limit_key))
+
+            if queue_limit then
+              local queue_locks = redis.call('llen', busy_key)
+
+              if queue_limit > queue_locks then
+                redis.call('rpush', busy_key, worker_name)
+                table.insert(available, queue)
+              end
+            else
+              redis.call('rpush', busy_key, worker_name)
+              table.insert(available, queue)
+            end
+          end
+        end
+
+        return available
+      LUA
+    end
+
+    def redis_release_script
+      <<-LUA
+        local namespace   = table.remove(ARGV, 1)..'limit_fetch:'
+        local worker_name = table.remove(ARGV, 1)
+        local queues      = ARGV
+
+        for _, queue in ipairs(queues) do
+          local busy_key = namespace..'busy:'..queue
+          redis.call('lrem', busy_key, 1, worker_name)
+        end
+      LUA
+    end
+  end
+end
diff --git a/lib/sidekiq/limit_fetch/global/semaphore.rb b/lib/sidekiq/limit_fetch/global/semaphore.rb
new file mode 100644
index 0000000..5c3e3be
--- /dev/null
+++ b/lib/sidekiq/limit_fetch/global/semaphore.rb
@@ -0,0 +1,38 @@
+module Sidekiq::LimitFetch::Global
+  class Semaphore
+    PREFIX = 'limit_fetch'
+
+    def initialize(name)
+      @name = name
+    end
+
+    def limit
+      value = Sidekiq.redis {|it| it.get "#{PREFIX}:limit:#@name" }
+      value.to_i if value
+    end
+
+    def limit=(value)
+      Sidekiq.redis {|it| it.set "#{PREFIX}:limit:#@name", value }
+    end
+
+    def acquire
+      Selector.acquire([@name]).size > 0
+    end
+
+    def release
+      Selector.release [@name]
+    end
+
+    def busy
+      Sidekiq.redis {|it| it.llen "#{PREFIX}:busy:#@name" }
+    end
+
+    def pause
+      Sidekiq.redis {|it| it.set "#{PREFIX}:pause:#@name", true }
+    end
+
+    def continue
+      Sidekiq.redis {|it| it.del "#{PREFIX}:pause:#@name" }
+    end
+  end
+end
diff --git a/lib/sidekiq/limit_fetch/local/selector.rb b/lib/sidekiq/limit_fetch/local/selector.rb
new file mode 100644
index 0000000..28ae200
--- /dev/null
+++ b/lib/sidekiq/limit_fetch/local/selector.rb
@@ -0,0 +1,19 @@
+module Sidekiq::LimitFetch::Local
+  module Selector
+    extend self
+
+    def acquire(names)
+      queues(names).select(&:acquire).map(&:name)
+    end
+
+    def release(names)
+      queues(names).each(&:release)
+    end
+
+    private
+
+    def queues(names)
+      names.map {|name| Sidekiq::Queue[name] }
+    end
+  end
+end
diff --git a/lib/sidekiq/limit_fetch/local/semaphore.rb b/lib/sidekiq/limit_fetch/local/semaphore.rb
new file mode 100644
index 0000000..d0b391c
--- /dev/null
+++ b/lib/sidekiq/limit_fetch/local/semaphore.rb
@@ -0,0 +1,39 @@
+module Sidekiq::LimitFetch::Local
+  class Semaphore
+    attr_reader :limit, :busy
+
+    def initialize(name)
+      @name = name
+      @lock = Mutex.new
+      @busy = 0
+      @paused = false
+    end
+
+    def limit=(value)
+      @lock.synchronize do
+        @limit = value
+      end
+    end
+
+    def acquire
+      return if @paused
+      @lock.synchronize do
+        @busy += 1 if not @limit or @limit > @busy
+      end
+    end
+
+    def release
+      @lock.synchronize do
+        @busy -= 1
+      end
+    end
+
+    def pause
+      @paused = true
+    end
+
+    def continue
+      @paused = false
+    end
+  end
+end
diff --git a/lib/sidekiq/limit_fetch/queues.rb b/lib/sidekiq/limit_fetch/queues.rb
new file mode 100644
index 0000000..5ba95dc
--- /dev/null
+++ b/lib/sidekiq/limit_fetch/queues.rb
@@ -0,0 +1,57 @@
+class Sidekiq::LimitFetch
+  class Queues
+    THREAD_KEY = :acquired_queues
+    attr_reader :selector
+
+    def initialize(options)
+      @queues = options[:queues]
+      options[:strict] ? strict_order! : weighted_order!
+
+      set_selector options[:global]
+      set_limits options[:limits]
+    end
+
+    def acquire
+      @selector.acquire(ordered_queues)
+        .tap {|it| save it }
+        .map {|it| "queue:#{it}" }
+    end
+    
+    def release_except(full_name)
+      @selector.release restore.delete_if {|name| full_name.to_s.include? name }
+    end
+
+    private
+
+    def set_selector(global)
+      @selector = global ? Global::Selector : Local::Selector
+    end
+
+    def set_limits(limits)
+      ordered_queues.each do |name|
+        Sidekiq::Queue[name].tap do |it|
+          it.limit = (limits || {})[name]
+        end
+      end
+    end
+
+    def strict_order!
+      @queues.uniq!
+      def ordered_queues; @queues end
+    end
+
+    def weighted_order!
+      def ordered_queues; @queues.shuffle.uniq end
+    end
+
+    def save(queues)
+      Thread.current[THREAD_KEY] = queues
+    end
+
+    def restore
+      Thread.current[THREAD_KEY]
+    ensure
+      Thread.current[THREAD_KEY] = nil
+    end
+  end
+end
diff --git a/lib/sidekiq/limit_fetch/semaphore.rb b/lib/sidekiq/limit_fetch/semaphore.rb
deleted file mode 100644
index 695bc2f..0000000
--- a/lib/sidekiq/limit_fetch/semaphore.rb
+++ /dev/null
@@ -1,36 +0,0 @@
-class Sidekiq::LimitFetch::Semaphore
-  attr_reader :limit, :busy
-
-  def initialize
-    @lock = Mutex.new
-    @busy = 0
-    @paused = false
-  end
-
-  def limit=(value)
-    @lock.synchronize do
-      @limit = value
-    end
-  end
-
-  def acquire
-    return if @paused
-    @lock.synchronize do
-      @busy += 1 if not @limit or @limit > @busy
-    end
-  end
-
-  def release
-    @lock.synchronize do
-      @busy -= 1
-    end
-  end
-
-  def pause
-    @paused = true
-  end
-
-  def continue
-    @paused = false
-  end
-end
diff --git a/lib/sidekiq/limit_fetch/unit_of_work.rb b/lib/sidekiq/limit_fetch/unit_of_work.rb
index 42b6277..6851d1c 100644
--- a/lib/sidekiq/limit_fetch/unit_of_work.rb
+++ b/lib/sidekiq/limit_fetch/unit_of_work.rb
@@ -1,16 +1,12 @@
-Sidekiq::LimitFetch::UnitOfWork = Struct.new :queue_wrapper, :message do
-  extend Forwardable
+module Sidekiq
+  class LimitFetch::UnitOfWork < BasicFetch::UnitOfWork
+    def acknowledge
+      Queue[queue_name].release
+    end
 
-  def_delegator :queue_wrapper, :full_name, :queue
-  def_delegator :queue_wrapper, :name, :queue_name
-  def_delegator :queue_wrapper, :release
-
-  def acknowledge
-    release
-  end
-
-  def requeue
-    release
-    Sidekiq.redis {|it| it.rpush queue, message }
+    def requeue
+      super
+      acknowledge
+    end
   end
 end
diff --git a/spec/limit_fetch_spec.rb b/spec/limit_fetch_spec.rb
deleted file mode 100644
index 5f8cdb1..0000000
--- a/spec/limit_fetch_spec.rb
+++ /dev/null
@@ -1,81 +0,0 @@
-require 'spec_helper'
-
-describe Sidekiq::LimitFetch do
-  before :each do
-    Sidekiq.redis do |it|
-      it.del 'queue:example1'
-      it.rpush 'queue:example1', 'task'
-      it.expire 'queue:example1', 30
-    end
-  end
-
-  def queues(fetcher)
-    fetcher.available_queues.map(&:full_name)
-  end
-
-  def new_fetcher(options={})
-    described_class.new options.merge queues: %w(example1 example1 example2 example2)
-  end
-
-  it 'should retrieve weighted queues' do
-    fetcher = new_fetcher
-    queues(fetcher).should =~ %w(queue:example1 queue:example2)
-  end
-
-  it 'should retrieve strictly ordered queues' do
-    fetcher = new_fetcher strict: true
-    queues(fetcher).should == %w(queue:example1 queue:example2)
-  end
-
-  it 'should retrieve only available queues' do
-    fetcher = new_fetcher strict: true, limits: { 'example1' => 2 }
-    queues = -> { fetcher.available_queues }
-
-    queues1 = queues.call
-    queues2 = queues.call
-    queues1.should have(2).items
-    queues2.should have(2).items
-    queues.call.should have(1).items
-
-    queues1.each(&:release)
-    queues.call.should have(2).items
-    queues.call.should have(1).items
-
-    queues2.each(&:release)
-    queues.call.should have(2).items
-    queues.call.should have(1).items
-  end
-
-  it 'should acquire lock on queue for excecution' do
-    fetcher = new_fetcher limits: { 'example1' => 1, 'example2' => 1 }
-    work = fetcher.retrieve_work
-    work.message.should == 'task'
-    work.queue.should == 'queue:example1'
-    work.queue_name.should == 'example1'
-
-    queues = fetcher.available_queues
-    queues.should have(1).item
-    queues.each(&:release)
-
-    work.requeue
-    work = fetcher.retrieve_work
-    work.message.should == 'task'
-    work.acknowledge
-
-    fetcher.available_queues.should have(2).items
-  end
-
-  it 'should set queue limits on the fly' do
-    Sidekiq::Queue['example1'].limit = 1
-    Sidekiq::Queue['example2'].limit = 2
-
-    fetcher = new_fetcher
-
-    fetcher.available_queues.should have(2).item
-    fetcher.available_queues.should have(1).item
-    fetcher.available_queues.should have(0).item
-
-    Sidekiq::Queue['example1'].limit = 2
-    fetcher.available_queues.should have(1).item
-  end
-end
diff --git a/spec/sidekiq/extensions/queue_spec.rb b/spec/sidekiq/extensions/queue_spec.rb
new file mode 100644
index 0000000..4695ee3
--- /dev/null
+++ b/spec/sidekiq/extensions/queue_spec.rb
@@ -0,0 +1,85 @@
+require 'spec_helper'
+
+describe Sidekiq::Queue do
+  context 'singleton' do
+    shared_examples :constructor do
+      it 'with default name' do
+        new_object = -> { described_class.send constructor }
+        new_object.call.should == new_object.call
+      end
+
+      it 'with given name' do
+        new_object = ->(name) { described_class.send constructor, name }
+        new_object.call('name').should == new_object.call('name')
+      end
+    end
+
+    context '.new' do
+      let(:constructor) { :new }
+      it_behaves_like :constructor
+    end
+
+    context '.[]' do
+      let(:constructor) { :[] }
+      it_behaves_like :constructor
+    end
+
+    context '#lock' do
+      let(:name) { 'example' }
+      let(:queue) { Sidekiq::Queue[name] }
+
+      shared_examples_for :lock do
+        it 'should be available' do
+          queue.acquire.should be
+        end
+
+        it 'should be pausable' do
+          queue.pause
+          queue.acquire.should_not be
+        end
+
+        it 'should be continuable' do
+          queue.pause
+          queue.continue
+          queue.acquire.should be
+        end
+
+        it 'should be limitable' do
+          queue.limit = 1
+          queue.acquire.should be
+          queue.acquire.should_not be
+        end
+
+        it 'should be resizable' do
+          queue.limit = 0
+          queue.acquire.should_not be
+          queue.limit = nil
+          queue.acquire.should be
+        end
+
+        it 'should be countable' do
+          queue.limit = 3
+          5.times { queue.acquire }
+          queue.busy.should == 3
+        end
+
+        it 'should be releasable' do
+          queue.acquire
+          queue.busy.should == 1
+          queue.release
+          queue.busy.should == 0
+        end
+      end
+
+      context 'global' do
+        before(:all) { Sidekiq.options[:global] = true }
+        it_behaves_like :lock
+      end
+
+      context 'local' do
+        before(:all) { Sidekiq.options[:global] = false }
+        it_behaves_like :lock
+      end
+    end
+  end
+end
diff --git a/spec/sidekiq/limit_fetch/queue_spec.rb b/spec/sidekiq/limit_fetch/queue_spec.rb
deleted file mode 100644
index 826179b..0000000
--- a/spec/sidekiq/limit_fetch/queue_spec.rb
+++ /dev/null
@@ -1,72 +0,0 @@
-require 'spec_helper'
-
-describe Sidekiq::Queue do
-  context 'singleton' do
-    shared_examples :constructor do
-      it 'with default name' do
-        new_object = -> { described_class.send constructor }
-        new_object.call.should == new_object.call
-      end
-
-      it 'with given name' do
-        new_object = ->(name) { described_class.send constructor, name }
-        new_object.call('name').should == new_object.call('name')
-      end
-    end
-
-    context '.new' do
-      let(:constructor) { :new }
-      it_behaves_like :constructor
-    end
-
-    context '.[]' do
-      let(:constructor) { :[] }
-      it_behaves_like :constructor
-    end
-
-    context '#acquire' do
-      let(:queue) { Sidekiq::Queue['example'] }
-
-      it 'should be available' do
-        queue.acquire.should be
-      end
-
-      it 'should be pausable' do
-        queue.pause
-        queue.acquire.should_not be
-      end
-
-      it 'should be continuable' do
-        queue.pause
-        queue.continue
-        queue.acquire.should be
-      end
-
-      it 'should be limitable' do
-        queue.limit = 1
-        queue.acquire.should be
-        queue.acquire.should_not be
-      end
-
-      it 'should be resizable' do
-        queue.limit = 0
-        queue.acquire.should_not be
-        queue.limit = nil
-        queue.acquire.should be
-      end
-
-      it 'should be countable' do
-        queue.limit = 3
-        5.times { queue.acquire }
-        queue.busy.should == 3
-      end
-
-      it 'should be releasable' do
-        queue.acquire
-        queue.busy.should == 1
-        queue.release
-        queue.busy.should == 0
-      end
-    end
-  end
-end
diff --git a/spec/sidekiq/limit_fetch/queues_spec.rb b/spec/sidekiq/limit_fetch/queues_spec.rb
new file mode 100644
index 0000000..5647f8f
--- /dev/null
+++ b/spec/sidekiq/limit_fetch/queues_spec.rb
@@ -0,0 +1,75 @@
+require 'spec_helper'
+
+describe Sidekiq::LimitFetch::Queues do
+  subject { described_class.new options }
+
+  let(:queues) { %w[queue1 queue2] }
+  let(:limits) {{ 'queue1' => 3 }}
+  let(:strict) { true }
+  let(:global) { false }
+
+  let(:options) do
+    { queues: queues, limits: limits, strict: strict, global: global }
+  end
+
+  after(:each ) do
+    Thread.current[:available_queues] = nil
+  end
+
+  shared_examples_for :selector do
+    it 'should acquire queues' do
+      subject.acquire
+      Sidekiq::Queue['queue1'].busy.should == 1
+      Sidekiq::Queue['queue2'].busy.should == 1
+    end
+
+    it 'should release queues' do
+      subject.acquire
+      subject.release_except nil
+      Sidekiq::Queue['queue1'].busy.should == 0
+      Sidekiq::Queue['queue2'].busy.should == 0
+    end
+
+    it 'should release queues except selected' do
+      subject.acquire
+      subject.release_except 'queue:queue1'
+      Sidekiq::Queue['queue1'].busy.should == 1
+      Sidekiq::Queue['queue2'].busy.should == 0
+    end
+  end
+  
+  context 'without global flag' do
+    it_should_behave_like :selector
+
+    it 'without global flag should be local' do
+      subject.selector.should == Sidekiq::LimitFetch::Local::Selector
+    end
+  end
+
+  context 'with global flag' do
+    let(:global) { true }
+    it_should_behave_like :selector
+
+    it 'should use global selector' do
+      subject.selector.should == Sidekiq::LimitFetch::Global::Selector
+    end
+  end
+
+  it 'should set limits' do
+    subject
+    Sidekiq::Queue['queue1'].limit.should == 3
+    Sidekiq::Queue['queue2'].limit.should_not be
+  end
+
+  context 'without strict flag' do
+    let(:strict) { false }
+
+    it 'should retrieve weighted queues' do
+      subject.ordered_queues.should =~ %w(queue1 queue2)
+    end
+  end
+
+  it 'with strict flag should retrieve strictly ordered queues' do
+    subject.ordered_queues.should == %w(queue1 queue2)
+  end
+end
diff --git a/spec/sidekiq/limit_fetch/semaphore_spec.rb b/spec/sidekiq/limit_fetch/semaphore_spec.rb
new file mode 100644
index 0000000..81a6bef
--- /dev/null
+++ b/spec/sidekiq/limit_fetch/semaphore_spec.rb
@@ -0,0 +1,68 @@
+require 'spec_helper'
+
+describe 'semaphore' do
+  shared_examples_for :semaphore do
+    it 'should have no limit by default' do
+      subject.limit.should_not be
+    end
+
+    it 'should set limit' do
+      subject.limit = 4
+      subject.limit.should == 4
+    end
+
+    it 'should acquire and count active tasks' do
+      3.times { subject.acquire }
+      subject.busy.should == 3
+    end
+
+    it 'should acquire tasks with regard to limit' do
+      subject.limit = 4
+      6.times { subject.acquire }
+      subject.busy.should == 4
+    end
+
+    it 'should release active tasks' do
+      6.times { subject.acquire }
+      3.times { subject.release }
+      subject.busy.should == 3
+    end
+
+    it 'should pause tasks' do
+      3.times { subject.acquire }
+      subject.pause
+      2.times { subject.acquire }
+      subject.busy.should == 3
+      2.times { subject.release }
+      subject.busy.should == 1
+    end
+
+    it 'should unpause tasks' do
+      subject.pause
+      3.times { subject.acquire }
+      subject.continue
+      2.times { subject.acquire }
+      subject.busy.should == 2
+    end
+  end
+
+  let(:name) { 'default' }
+
+  context 'local' do
+    subject { Sidekiq::LimitFetch::Local::Semaphore.new name }
+    it_behaves_like :semaphore
+  end
+
+  context 'global' do
+    subject { Sidekiq::LimitFetch::Global::Semaphore.new name }
+    it_behaves_like :semaphore
+
+    after :each do
+      Sidekiq.redis do |it|
+        it.del "limit_fetch:limit:#{name}"
+        it.del "limit_fetch:busy:#{name}"
+        it.del "limit_fetch:pause:#{name}"
+      end
+    end
+  end
+end
diff --git a/spec/sidekiq/limit_fetch_spec.rb b/spec/sidekiq/limit_fetch_spec.rb
new file mode 100644
index 0000000..465b4a6
--- /dev/null
+++ b/spec/sidekiq/limit_fetch_spec.rb
@@ -0,0 +1,47 @@
+require 'spec_helper'
+
+describe Sidekiq::LimitFetch do
+  before :each do
+    Sidekiq.redis do |it|
+      it.del 'queue:queue1'
+      it.rpush 'queue:queue1', 'task1'
+      it.rpush 'queue:queue1', 'task2'
+      it.expire 'queue:queue1', 30
+    end
+  end
+
+  subject { described_class.new options }
+  let(:options) {{ queues: queues, limits: limits, global: global }}
+  let(:queues) { %w(queue1 queue1 queue2 queue2) }
+  let(:limits) {{ 'queue1' => 1, 'queue2' => 2 }}
+  
+  shared_examples_for :strategy do
+    it 'should acquire lock on queue for execution' do
+      work = subject.retrieve_work
+      work.queue_name.should == 'queue1'
+      work.message.should == 'task1'
+
+      subject.retrieve_work.should_not be
+      work.requeue
+
+      work = subject.retrieve_work
+      work.message.should == 'task2'
+
+      subject.retrieve_work.should_not be
+      work.acknowledge
+
+      work = subject.retrieve_work
+      work.message.should == 'task1'
+    end
+  end
+
+  context 'global' do
+    let(:global) { true }
+    it_behaves_like :strategy
+  end
+
+  context 'local' do
+    let(:global) { false }
+    it_behaves_like :strategy
+  end
+end
diff --git a/spec/spec_helper.rb b/spec/spec_helper.rb
index 65b89d9..15d2a78 100644
--- a/spec/spec_helper.rb
+++ b/spec/spec_helper.rb
@@ -3,5 +3,17 @@ require 'sidekiq/limit_fetch'
 RSpec.configure do |config|
   config.before :each do
     Sidekiq::Queue.instance_variable_set :@instances, {}
+    Sidekiq.options[:global] = defined?(global) ? global : nil
+  
+    Sidekiq.redis do |it|
+      clean_redis = ->(queue) do
+        it.del "limit_fetch:limit:#{queue}"
+        it.del "limit_fetch:busy:#{queue}"
+        it.del "limit_fetch:pause:#{queue}"
+      end
+
+      clean_redis.call(name) if defined?(name)
+      queues.each(&clean_redis) if defined?(queues) and queues.is_a? Array
+    end
   end
 end