in_monitor_agent emits plugins info to use exisiting plugins. fix #667

lib/fluent/plugin/in_monitor_agent.rb

@@ -27,6 +27,8 @@ def initialize
 
     config_param :bind, :string, :default => '0.0.0.0'
     config_param :port, :integer, :default => 24220
+    config_param :tag, :string, :default => nil
+    config_param :emit_interval, :time, :default => 60
 
     class MonitorServlet < WEBrick::HTTPServlet::AbstractServlet
       def initialize(server, agent)
@@ -199,6 +201,36 @@ def process(req, res)
       end
     end
 
+    class TimerWatcher < Coolio::TimerWatcher
+      def initialize(interval, log, &callback)
+        @callback = callback
+        @log = log
+
+        # Avoid long shutdown time
+        @num_call = 0
+        if interval >= 10
+          min_interval = 10
+          @call_interval = interval / 10
+        else
+          min_interval = interval
+          @call_interval = 0
+        end
+
+        super(min_interval, true)
+      end
+
+      def on_timer
+        @num_call += 1
+        if @num_call >= @call_interval
+          @num_call = 0
+          @callback.call
+        end
+      rescue => e
+        @log.error e.to_s
+        @log.error_backtrace
+      end
+    end
+
     def start
       log.debug "listening monitoring http server on http://#{@bind}:#{@port}/api/plugins"
       @srv = WEBrick::HTTPServer.new({
@@ -214,6 +246,23 @@ def start
       @thread = Thread.new {
         @srv.start
       }
+      if @tag
+        log.debug "tag parameter is specified. Emit plugins info to '#{@tag}'"
+
+        @loop = Coolio::Loop.new
+        timer = TimerWatcher.new(@emit_interval, log) {
+          router.emit(@tag, Engine.now, {'plugins'.freeze => plugins_info_all})
+        }
+        @loop.attach(timer)
+        @thread_for_emit = Thread.new(&method(:run))
+      end
+    end
+
+    def run
+      @loop.run
+    rescue => e
+      log.error "unexpected error", :error => e.to_s
+      log.error_backtrace
     end
 
     def shutdown
@@ -225,6 +274,13 @@ def shutdown
         @thread.join
         @thread = nil
       end
+      if @tag
+        @loop.watchers.each { |w| w.detach }
+        @loop.stop
+        @loop = nil
+        @thread_for_emit.join
+        @thread_for_emit = nil
+      end
     end
 
     MONITOR_INFO = {