Implement metrics plugin mechanism

Signed-off-by: Hiroshi Hatake <hatake@calyptia.com>

lib/fluent/plugin.rb

@@ -36,8 +36,9 @@ module Plugin
     FORMATTER_REGISTRY = Registry.new(:formatter, 'fluent/plugin/formatter_',  dir_search_prefix: 'formatter_')
     STORAGE_REGISTRY   = Registry.new(:storage,   'fluent/plugin/storage_',    dir_search_prefix: 'storage_')
     SD_REGISTRY        = Registry.new(:sd,        'fluent/plugin/sd_',         dir_search_prefix: 'sd_')
+    METRICS_REGISTRY   = Registry.new(:metrics,   'fluent/plugin/metrics_',    dir_search_prefix: 'metrics_')
 
-    REGISTRIES = [INPUT_REGISTRY, OUTPUT_REGISTRY, FILTER_REGISTRY, BUFFER_REGISTRY, PARSER_REGISTRY, FORMATTER_REGISTRY, STORAGE_REGISTRY, SD_REGISTRY]
+    REGISTRIES = [INPUT_REGISTRY, OUTPUT_REGISTRY, FILTER_REGISTRY, BUFFER_REGISTRY, PARSER_REGISTRY, FORMATTER_REGISTRY, STORAGE_REGISTRY, SD_REGISTRY, METRICS_REGISTRY]
 
     def self.register_input(type, klass)
       register_impl('input', INPUT_REGISTRY, type, klass)
@@ -59,6 +60,10 @@ def self.register_sd(type, klass)
       register_impl('sd', SD_REGISTRY, type, klass)
     end
 
+    def self.register_metrics(type, klass)
+      register_impl('metrics', METRICS_REGISTRY, type, klass)
+    end
+
     def self.register_parser(type, klass_or_proc)
       if klass_or_proc.is_a?(Regexp)
         # This usage is not recommended for new API
@@ -121,6 +126,10 @@ def self.new_sd(type, parent: nil)
       new_impl('sd', SD_REGISTRY, type, parent)
     end
 
+    def self.new_metrics(type, parent: nil)
+      new_impl('metrics', METRICS_REGISTRY, type, parent)
+    end
+
     class << self
       # This should be defined for fluent-plugin-config-formatter type arguments.
       alias_method :new_service_discovery, :new_sd

lib/fluent/plugin/metrics.rb

@@ -0,0 +1,119 @@
+#
+# Fluentd
+#
+#    Licensed under the Apache License, Version 2.0 (the "License");
+#    you may not use this file except in compliance with the License.
+#    You may obtain a copy of the License at
+#
+#        http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS,
+#    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#    See the License for the specific language governing permissions and
+#    limitations under the License.
+#
+
+require 'socket'
+
+require 'fluent/plugin/base'
+
+require 'fluent/log'
+require 'fluent/unique_id'
+require 'fluent/plugin_id'
+
+module Fluent
+  module Plugin
+    class Metrics < Base
+      include PluginId
+      include PluginLoggerMixin
+      include UniqueId::Mixin
+
+      DEFAULT_TYPE = 'local'
+
+      configured_in :metrics
+
+      config_param :default_labels, :hash, default: {agent: "Fluentd", hostname: "#{Socket.gethostname}"}
+      config_param :labels, :hash, default: {}
+
+      attr_reader :use_gauge_metric
+      attr_reader :has_methods_for_gauge, :has_methods_for_counter
+
+      def initialize
+        super
+
+        @has_methods_for_counter = false
+        @has_methods_for_gauge = false
+        @use_gauge_metric = false
+      end
+
+      def configure(conf)
+        super
+
+        if use_gauge_metric
+          @has_methods_for_gauge = has_methods_for_gauge?
+        else
+          @has_methods_for_counter = has_methods_for_counter?
+        end
+      end
+
+      # Some metrics should be counted by gauge.
+      # ref: https://prometheus.io/docs/concepts/metric_types/#gauge
+      def use_gauge_metric=(use_gauge_metric=false)
+        @use_gauge_metric = use_gauge_metric
+      end
+
+      def create(namespace:, subsystem:,name:,help_text:,labels: {})
+        # This API is for cmetrics type.
+      end
+
+      def get(key)
+        raise NotImplementedError, "Implement this method in child class"
+      end
+
+      def inc(key)
+        raise NotImplementedError, "Implement this method in child class"
+      end
+
+      def dec(key)
+        raise NotImplementedError, "Implement this method in child class"
+      end
+
+      def add(key, value)
+        raise NotImplementedError, "Implement this method in child class"
+      end
+
+      def sub(key, value)
+        raise NotImplementedError, "Implement this method in child class"
+      end
+
+      def set(key, value)
+        raise NotImplementedError, "Implement this method in child class"
+      end
+
+      private
+
+      def has_methods_for_counter?
+        implemented_methods = self.class.instance_methods(false)
+
+        if [:get, :inc, :add].all? {|e| implemented_methods.include?(e)} &&
+           [:set].all?{|e| self.class.method_defined?(e)}
+          true
+        else
+          raise "BUG: metrics plugin on counter mode MUST implement `get`, `inc`, `add` methods. And aliased `set` methods should be aliased other methods"
+        end
+      end
+
+      def has_methods_for_gauge?
+        implemented_methods = self.class.instance_methods(false)
+
+        if [:get, :inc, :add].all? {|e| implemented_methods.include?(e)} &&
+           [:set, :dec, :sub].all?{|e| self.class.method_defined?(e)}
+          true
+        else
+          raise "BUG: metrics plugin on gauge mode MUST implement `get`, `inc`, and `add` methods. And `dec`, `sub`, and `set` methods should be aliased from other methods"
+        end
+      end
+    end
+  end
+end

lib/fluent/plugin/metrics_local.rb

@@ -0,0 +1,96 @@
+#
+# Fluentd
+#
+#    Licensed under the Apache License, Version 2.0 (the "License");
+#    you may not use this file except in compliance with the License.
+#    You may obtain a copy of the License at
+#
+#        http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS,
+#    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#    See the License for the specific language governing permissions and
+#    limitations under the License.
+#
+
+require 'fluent/plugin'
+require 'fluent/plugin/metrics'
+
+module Fluent
+  module Plugin
+    class LocalMetrics < Metrics
+      Fluent::Plugin.register_metrics('local', self)
+
+      def initialize
+        super
+        @store = Hash.new(0)
+        @monitor = Monitor.new
+      end
+
+      def configure(conf)
+        super
+
+        if use_gauge_metric
+          class << self
+            alias_method :dec, :dec_gauge
+            alias_method :set, :set_gauge
+            alias_method :sub, :sub_gauge
+          end
+        else
+          class << self
+            alias_method :set, :set_counter
+          end
+        end
+      end
+
+      def multi_workers_ready?
+        true
+      end
+
+      def get(key)
+        @monitor.synchronize do
+          @store[key.to_s]
+        end
+      end
+
+      def inc(key)
+        @monitor.synchronize do
+          @store[key.to_s] += 1
+        end
+      end
+
+      def dec_gauge(key)
+        @monitor.synchronize do
+          @store[key.to_s] -= 1
+        end
+      end
+
+      def add(key, value)
+        @monitor.synchronize do
+          @store[key.to_s] += value
+        end
+      end
+
+      def sub_gauge(key, value)
+        @monitor.synchronize do
+          @store[key.to_s] -= value
+        end
+      end
+
+      def set_counter(key, value)
+        return if @store[key.to_s] > value
+
+        @monitor.synchronize do
+          @store[key.to_s] = value
+        end
+      end
+
+      def set_gauge(key, value)
+        @monitor.synchronize do
+          @store[key.to_s] = value
+        end
+      end
+    end
+  end
+end

lib/fluent/plugin_helper.rb

@@ -32,6 +32,7 @@
 require 'fluent/plugin_helper/record_accessor'
 require 'fluent/plugin_helper/compat_parameters'
 require 'fluent/plugin_helper/service_discovery'
+require 'fluent/plugin_helper/metrics'
 
 module Fluent
   module PluginHelper

lib/fluent/plugin_helper/metrics.rb

@@ -0,0 +1,66 @@
+#
+# Fluentd
+#
+#    Licensed under the Apache License, Version 2.0 (the "License");
+#    you may not use this file except in compliance with the License.
+#    You may obtain a copy of the License at
+#
+#        http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS,
+#    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#    See the License for the specific language governing permissions and
+#    limitations under the License.
+#
+
+require 'forwardable'
+
+require 'fluent/plugin'
+require 'fluent/plugin/metrics'
+require 'fluent/plugin_helper/timer'
+require 'fluent/config/element'
+require 'fluent/configurable'
+require 'fluent/system_config'
+
+module Fluent
+  module PluginHelper
+    module Metrics
+      include Fluent::SystemConfig::Mixin
+
+      def initialize
+        super
+        @_metrics = {} # usage => metrics_state
+      end
+
+      def configure(conf)
+        super
+      end
+
+      def metrics_create(namespace: "Fluentd", subsystem: "metrics", name:, help_text:, labels: {}, prefer_gauge: false)
+        metrics = if system_config.metrics
+                    Fluent::Plugin.new_metrics(system_config.metrics[:@type], parent: self)
+                  else
+                    Fluent::Plugin.new_metrics(Fluent::Plugin::Metrics::DEFAULT_TYPE, parent: self)
+                  end
+        config = if system_config.metrics
+                   system_config.metrics.corresponding_config_element
+                 else
+                   Fluent::Config::Element.new('metrics', '', {'@type' => Fluent::Plugin::Metrics::DEFAULT_TYPE}, [])
+                 end
+        metrics.use_gauge_metric = prefer_gauge
+        metrics.configure(config)
+        metrics.create(namespace: namespace, subsystem: subsystem, name: name, help_text: help_text, labels: labels)
+
+        @_metrics["#{self.plugin_id}_#{namespace}_#{subsystem}_#{name}"] = metrics
+
+        metrics
+      end
+
+      def terminate
+        @_metrics = {}
+        super
+      end
+    end
+  end
+end

lib/fluent/system_config.rb

@@ -27,7 +27,8 @@ class SystemConfig
       :log_event_verbose, :ignore_repeated_log_interval, :ignore_same_log_interval,
       :without_source, :rpc_endpoint, :enable_get_dump, :process_name,
       :file_permission, :dir_permission, :counter_server, :counter_client,
-      :strict_config_value, :enable_msgpack_time_support, :disable_shared_socket
+      :strict_config_value, :enable_msgpack_time_support, :disable_shared_socket,
+      :metrics
     ]
 
     config_param :workers,   :integer, default: 1
@@ -93,6 +94,11 @@ class SystemConfig
       config_param :timeout, :time, default: nil
     end
 
+    config_section :metrics, multi: false do
+      config_param :@type, :string, default: "local"
+      config_param :labels, :hash, default: {}
+    end
+
     def self.create(conf, strict_config_value=false)
       systems = conf.elements(name: 'system')
       return SystemConfig.new if systems.empty?