Make more kindly error message when occurring worker_ids collisions

Signed-off-by: Hiroshi Hatake <[email protected]>

lib/fluent/root_agent.rb

@@ -65,6 +65,10 @@ def initialize(log:, system_config: SystemConfig.new)
 
     def configure(conf)
       used_worker_ids = []
+      available_worker_ids = []
+      0.step(Fluent::Engine.system_config.workers - 1, 1).each do |id|
+        available_worker_ids << id
+      end
       # initialize <worker> elements
       conf.elements(name: 'worker').each do |e|
         target_worker_id_str = e.arg
@@ -84,8 +88,9 @@ def configure(conf)
             if target_worker_id < 0 || target_worker_id > (Fluent::Engine.system_config.workers - 1)
               raise Fluent::ConfigError, "worker id #{target_worker_id} specified by <worker> directive is not allowed. Available worker id is between 0 and #{(Fluent::Engine.system_config.workers - 1)}"
             end
+            available_worker_ids.delete(worker_id) if available_worker_ids.include?(worker_id)
             if used_worker_ids.include?(worker_id)
-              raise Fluent::ConfigError, "specified worker_id<#{worker_id}> collisions is detected on <worker> directive. Available worker id is between 0 and #{(Fluent::Engine.system_config.workers - 1)} without collisions"
+              raise Fluent::ConfigError, "specified worker_id<#{worker_id}> collisions is detected on <worker> directive. Available worker id(s): #{available_worker_ids}"
             end
             used_worker_ids << worker_id
 

test/test_root_agent.rb

@@ -698,7 +698,7 @@ def configure_ra(conf_str)
     end
 
     test 'raises configuration error for worker id collisions on multi workers syntax' do
-      errmsg = "specified worker_id<2> collisions is detected on <worker> directive. Available worker id is between 0 and 3 without collisions"
+      errmsg = "specified worker_id<2> collisions is detected on <worker> directive. Available worker id(s): [3]"
       assert_raise Fluent::ConfigError.new(errmsg) do
         conf = <<-EOC
 <worker 0-2>
@@ -710,6 +710,19 @@ def configure_ra(conf_str)
       end
     end
 
+    test 'raises configuration error for worker id collisions on multi workers syntax when multi avaliable worker_ids are left' do
+      errmsg = "specified worker_id<1> collisions is detected on <worker> directive. Available worker id(s): [2, 3]"
+      assert_raise Fluent::ConfigError.new(errmsg) do
+        conf = <<-EOC
+<worker 0-1>
+</worker>
+<worker 1-3>
+</worker>
+EOC
+        configure_ra(conf)
+      end
+    end
+
     test 'raises configuration error for too big worker id on invalid reversed multi workers syntax' do
       errmsg = "greater first_worker_id<3> than last_worker_id<0> specified by <worker> directive is not allowed. Available multi worker assign syntax is <smaller_worker_id>-<greater_worker_id>"
       assert_raise Fluent::ConfigError.new(errmsg) do