Use the job class as the default concurrency key if none is provided (#…

…1145)

* Add a default concurrency key if not specified

* Address review feedback

* Make the default concurrency key easibly monkey-patchable
* Support a nil concurrency key callable

* Fix typo

* Use the class name as the default concurrency key

* Note it can be disabled with a nil key

---------

Co-authored-by: Ben Sheldon [he/him] <bensheldon@gmail.com>

README.md

@@ -511,12 +511,22 @@ class MyJob < ApplicationJob
 
     # A unique key to be globally locked against.
     # Can be String or Lambda/Proc that is invoked in the context of the job.
+    #
+    # If a key is not provided GoodJob will use the job class name.
+    #
+    # To disable concurrency control, for example in a subclass, set the
+    # key explicitly to nil (e.g. `key: nil` or `key: -> { nil }`)
+    #
+    # If you provide a custom concurrency key (for example, if one of your arguments
+    # is transient) make sure that it is sufficiently unique across jobs and queues
+    # by adding the job class or queue to the key yourself, if needed.
+    #
     # Note: Arguments passed to #perform_later can be accessed through Active Job's `arguments` method
     # which is an array containing positional arguments and, optionally, a kwarg hash.
-    key: -> { "MyJob-#{arguments.first}-#{arguments.last[:version]}" } #  MyJob.perform_later("Alice", version: 'v2') => "MyJob-Alice-v2"
+    key: -> { "#{self.class.name}-#{queue_name}-#{arguments.first}-#{arguments.last[:version]}" } #  MyJob.perform_later("Alice", version: 'v2') => "MyJob-default-Alice-v2"
   )
 
-  def perform(first_name)
+  def perform(first_name, version:)
     # do work
   end
 end
@@ -525,8 +535,8 @@ end
 When testing, the resulting concurrency key value can be inspected:
 
 ```ruby
-job = MyJob.perform_later("Alice")
-job.good_job_concurrency_key #=> "MyJob-Alice"
+job = MyJob.perform_later("Alice", version: 'v1')
+job.good_job_concurrency_key #=> "MyJob-default-Alice-v1"
 ```
 
 #### How concurrency controls work

lib/good_job/active_job_extensions/concurrency.rb

@@ -96,6 +96,8 @@ def good_job_concurrency_key
       # Generates the concurrency key from the configuration
       # @return [Object] concurrency key
       def _good_job_concurrency_key
+        return _good_job_default_concurrency_key unless self.class.good_job_concurrency_config.key?(:key)
+
         key = self.class.good_job_concurrency_config[:key]
         return if key.blank?
 
@@ -105,6 +107,12 @@ def _good_job_concurrency_key
         key
       end
 
+      # Generates the default concurrency key when the configuration doesn't provide one
+      # @return [String] concurrency key
+      def _good_job_default_concurrency_key
+        self.class.name.to_s
+      end
+
       private
 
       def good_job_enqueue_concurrency_check(job, on_abort:, on_enqueue:)

spec/lib/good_job/active_job_extensions/concurrency_spec.rb

@@ -26,7 +26,7 @@ def perform(name:)
     end
   end
 
-  describe 'when concurrency key is nil' do
+  describe 'when concurrency key returns nil' do
     it 'does not limit concurrency' do
       TestJob.good_job_control_concurrency_with(
         total_limit: -> { 1 },
@@ -38,6 +38,18 @@ def perform(name:)
     end
   end
 
+  describe 'when concurrency key is nil' do
+    it 'does not limit concurrency' do
+      TestJob.good_job_control_concurrency_with(
+        total_limit: -> { 1 },
+        key: nil
+      )
+
+      expect(TestJob.perform_later(name: "Alice")).to be_present
+      expect(TestJob.perform_later(name: "Alice")).to be_present
+    end
+  end
+
   describe '.good_job_control_concurrency_with' do
     describe 'total_limit:', :skip_rails_5 do
       before do
@@ -194,6 +206,22 @@ def perform
       end
     end
 
+    context 'when no key is specified' do
+      before do
+        stub_const 'TestJob', (Class.new(ActiveJob::Base) do
+          include GoodJob::ActiveJobExtensions::Concurrency
+
+          def perform(name)
+          end
+        end)
+      end
+
+      it 'uses the class name as the default concurrency key' do
+        job = TestJob.perform_later("Alice")
+        expect(job.good_job_concurrency_key).to eq('TestJob')
+      end
+    end
+
     describe '#perform_later' do
       before do
         stub_const 'TestJob', (Class.new(ActiveJob::Base) do