Configure multiple dispatchers, just like workers

This will be useful later when we support cron jobs and need
a specific dispatcher to handle these.

Author: rosa

lib/solid_queue/configuration.rb

@@ -22,9 +22,9 @@ def initialize(mode: :work, load_from: nil)
 
     def processes
       case mode
-      when :dispatch then dispatcher
+      when :dispatch then dispatchers
       when :work     then workers
-      when :all      then [ dispatcher ] + workers
+      when :all      then dispatchers + workers
       else           raise "Invalid mode #{mode}"
       end
     end
@@ -40,9 +40,11 @@ def workers
       end
     end
 
-    def dispatcher
+    def dispatchers
       if mode.in? %i[ dispatch all]
-        SolidQueue::Dispatcher.new(**dispatcher_options)
+        dispatchers_options.flat_map do |dispatcher_options|
+          SolidQueue::Dispatcher.new(**dispatcher_options)
+        end
       end
     end
 
@@ -62,11 +64,13 @@ def config_from(file_or_hash, env: Rails.env)
       end
 
       def workers_options
-        @workers_options ||= (raw_config[:workers] || [ WORKER_DEFAULTS ]).map { |options| options.dup.symbolize_keys }
+        @workers_options ||= (raw_config[:workers] || [ WORKER_DEFAULTS ])
+          .map { |options| options.dup.symbolize_keys }
       end
 
-      def dispatcher_options
-        (raw_config[:dispatcher] || {}).with_defaults(DISPATCHER_DEFAULTS)
+      def dispatchers_options
+        @dispatchers_options ||= (raw_config[:dispatchers] || [ DISPATCHER_DEFAULTS ])
+          .map { |options| options.dup.symbolize_keys }
       end
 
       def load_config_from(file_or_hash)

test/dummy/config/solid_queue.yml

@@ -4,9 +4,9 @@ default: &default
       threads: 3
     - queues: default
       threads: 5
-  dispatcher:
-    polling_interval: 1
-    batch_size: 500
+  dispatchers:
+    - polling_interval: 1
+      batch_size: 500
 
 development:
   <<: *default

test/integration/concurrency_controls_test.rb

@@ -10,7 +10,7 @@ class ConcurrencyControlsTest < ActiveSupport::TestCase
     default_worker = { queues: "default", polling_interval: 1, processes: 3, threads: 2 }
     dispatcher = { polling_interval: 1, batch_size: 200, concurrency_maintenance_interval: 1 }
 
-    @pid = run_supervisor_as_fork(mode: :all, load_configuration_from: { workers: [ default_worker ], dispatcher: dispatcher })
+    @pid = run_supervisor_as_fork(mode: :all, load_configuration_from: { workers: [ default_worker ], dispatchers: [ dispatcher ] })
 
     wait_for_registered_processes(5, timeout: 0.5.second) # 3 workers working the default queue + dispatcher + supervisor
   end

test/unit/configuration_test.rb

@@ -6,25 +6,25 @@ class ConfigurationTest < ActiveSupport::TestCase
     assert_equal 2, configuration.processes.count
 
     assert_equal 1, configuration.workers.count
-    assert configuration.dispatcher.present?
+    assert_equal 1, configuration.dispatchers.count
 
     assert_equal [ "*" ], configuration.workers.first.queues
-    assert_equal SolidQueue::Configuration::DISPATCHER_DEFAULTS[:batch_size], configuration.dispatcher.batch_size
+    assert_equal SolidQueue::Configuration::DISPATCHER_DEFAULTS[:batch_size], configuration.dispatchers.first.batch_size
   end
 
   test "read configuration from default file" do
     configuration = SolidQueue::Configuration.new(mode: :all)
     assert 3, configuration.processes.count
     assert_equal 2, configuration.workers.count
-    assert configuration.dispatcher.present?
+    assert_equal 1, configuration.dispatchers.count
   end
 
   test "provide configuration as a hash and fill defaults" do
     background_worker = { queues: "background", polling_interval: 10 }
     config_as_hash = { workers: [ background_worker, background_worker ] }
     configuration = SolidQueue::Configuration.new(mode: :all, load_from: config_as_hash)
 
-    assert_equal SolidQueue::Configuration::DISPATCHER_DEFAULTS[:polling_interval], configuration.dispatcher.polling_interval
+    assert_equal SolidQueue::Configuration::DISPATCHER_DEFAULTS[:polling_interval], configuration.dispatchers.first.polling_interval
     assert_equal 2, configuration.workers.count
     assert_equal [ "background" ], configuration.workers.flat_map(&:queues).uniq
     assert_equal [ 10 ], configuration.workers.map(&:polling_interval).uniq