log: add caller plugin-id about emitting error events

It would be helpful if we could know what plugin emitted the
error event.

#4567

We need to care about the compatibility.
This signature change would not break compatibility.

However, I'm concerned that `caller_plugin_id` has a race
condition, although I don't confirm it.
It looks to me that the id can be another plugin-id running
concurrently...
It is not the issue with this fix, it is the issue of the
existing implementation.

Signed-off-by: Daijiro Fukuda <[email protected]>

Author: daipom

lib/fluent/agent.rb

@@ -159,7 +159,7 @@ def add_filter(type, pattern, conf)
     end
 
     # For handling invalid record
-    def emit_error_event(tag, time, record, error)
+    def emit_error_event(tag, time, record, error, plugin_id: nil)
     end
 
     def handle_emits_error(tag, es, error)

lib/fluent/event_router.rb

@@ -123,7 +123,7 @@ def emit_stream(tag, es)
     end
 
     def emit_error_event(tag, time, record, error)
-      @emit_error_handler.emit_error_event(tag, time, record, error)
+      @emit_error_handler.emit_error_event(tag, time, record, error, plugin_id: @caller_plugin_id)
     end
 
     def match?(tag)

lib/fluent/label.rb

@@ -35,8 +35,8 @@ def configure(conf)
       end
     end
 
-    def emit_error_event(tag, time, record, e)
-      @root_agent.emit_error_event(tag, time, record, e)
+    def emit_error_event(tag, time, record, e, plugin_id: nil)
+      @root_agent.emit_error_event(tag, time, record, e, plugin_id: plugin_id)
     end
 
     def handle_emits_error(tag, es, e)

lib/fluent/root_agent.rb

@@ -341,8 +341,9 @@ def find_label(label_name)
       end
     end
 
-    def emit_error_event(tag, time, record, error)
+    def emit_error_event(tag, time, record, error, plugin_id: nil)
       error_info = {error: error, location: (error.backtrace ? error.backtrace.first : nil), tag: tag, time: time}
+      error_info[:plugin_id] = plugin_id if plugin_id
       if @error_collector
         # A record is not included in the logs because <@ERROR> handles it. This warn is for the notification
         log.warn "send an error event to @ERROR:", error_info