Class: Fluent::RootAgent

Inherits:
Agent
  • Object
show all
Defined in:
lib/fluent/root_agent.rb

Overview

Fluentd forms a tree structure to manage plugins:

                 RootAgent
                     |
        +------------+-------------+-------------+
        |            |             |             |
     <label>      <source>      <filter>      <match>
        |
   +----+----+
   |         |
<filter>   <match>

Relation:

  • RootAgent has many <label>, <source>, <filter> and <match>

  • <label> has many <match> and <filter>

Next step: ‘fluentd/agent.rb` Next step: ’fluentd/label.rb’

Defined Under Namespace

Classes: RootAgentProxyWithoutErrorCollector

Constant Summary collapse

ERROR_LABEL = 
"@ERROR".freeze

Constants included from Configurable

Configurable::CONFIG_TYPE_REGISTRY

Instance Attribute Summary collapse

Attributes inherited from Agent

#context, #error_collector, #event_router, #filters, #log, #outputs

Instance Method Summary collapse

Methods inherited from Agent

#add_filter, #add_match, #lifecycle_control_list

Methods included from Configurable

#config, #configure_proxy_generate, #configured_section_create, included, lookup_type, register_type

Constructor Details

#initialize(log:, system_config: SystemConfig.new) ⇒ RootAgent

Returns a new instance of RootAgent.



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# File 'lib/fluent/root_agent.rb', line 50

def initialize(log:, system_config: SystemConfig.new)
  super(log: log)

  @labels = {}
  @inputs = []
  @suppress_emit_error_log_interval = 0
  @next_emit_error_log_time = nil
  @without_source = false

  suppress_interval(system_config.emit_error_log_interval) unless system_config.emit_error_log_interval.nil?
  @without_source = system_config.without_source unless system_config.without_source.nil?
end

Instance Attribute Details

#inputs ⇒ Object (readonly)

Returns the value of attribute inputs.



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# File 'lib/fluent/root_agent.rb', line 63

def inputs
  @inputs
end

#labels ⇒ Object (readonly)

Returns the value of attribute labels.



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# File 'lib/fluent/root_agent.rb', line 64

def labels
  @labels
end

Instance Method Details

#add_label(name) ⇒ Object

Raises:



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# File 'lib/fluent/root_agent.rb', line 251

def add_label(name)
  label = Label.new(name, log: log)
  raise ConfigError, "Section <label #{name}> appears twice" if @labels[name]
  label.root_agent = self
  @labels[name] = label
end

#add_source(type, conf) ⇒ Object 



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# File 'lib/fluent/root_agent.rb', line 237

def add_source(type, conf)
  log.info :worker0, "adding source", type: type

  input = Plugin.new_input(type)
  # <source> emits events to the top-level event router (RootAgent#event_router).
  # Input#configure overwrites event_router to a label's event_router if it has `@label` parameter.
  # See also 'fluentd/plugin/input.rb'
  input.context_router = @event_router
  input.configure(conf)
  @inputs << input

  input
end

#configure(conf) ⇒ Object 



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# File 'lib/fluent/root_agent.rb', line 66

def configure(conf)
  error_label_config = nil

  # initialize <label> elements before configuring all plugins to avoid 'label not found' in input, filter and output.
  label_configs = {}
  conf.elements(name: 'label').each { |e|
    name = e.arg
    raise ConfigError, "Missing symbol argument on <label> directive" if name.empty?

    if name == ERROR_LABEL
      error_label_config = e
    else
      add_label(name)
      label_configs[name] = e
    end
  }
  # Call 'configure' here to avoid 'label not found'
  label_configs.each { |name, e| @labels[name].configure(e) }
  setup_error_label(error_label_config) if error_label_config

  super

  # initialize <source> elements
  if @without_source
    log.info :worker0, "'--without-source' is applied. Ignore <source> sections"
  else
    conf.elements(name: 'source').each { |e|
      type = e['@type']
      raise ConfigError, "Missing '@type' parameter on <source> directive" unless type
      add_source(type, e)
    }
  end
end

#emit_error_event(tag, time, record, error) ⇒ Object 



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# File 'lib/fluent/root_agent.rb', line 266

def emit_error_event(tag, time, record, error)
  error_info = {error: error, tag: tag, time: time}
  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
    @error_collector.emit(tag, time, record)
  else
    error_info[:record] = record
    log.warn "dump an error event:", error_info
  end
end

#find_label(label_name) ⇒ Object 



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# File 'lib/fluent/root_agent.rb', line 258

def find_label(label_name)
  if label = @labels[label_name]
    label
  else
    raise ArgumentError, "#{label_name} label not found"
  end
end

#flush! ⇒ Object 



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# File 'lib/fluent/root_agent.rb', line 149

def flush!
  log.info "flushing all buffer forcedly"
  flushing_threads = []
  lifecycle(desc: true) do |instance|
    if instance.respond_to?(:force_flush)
      t = Thread.new do
        Thread.current.abort_on_exception = true
        begin
          instance.force_flush
        rescue => e
          log.warn "unexpected error while flushing buffer", plugin: instance.class, plugin_id: instance.plugin_id, error: e
          log.warn_backtrace
        end
      end
      flushing_threads << t
    end
  end
  flushing_threads.each{|t| t.join }
end

#handle_emits_error(tag, es, error) ⇒ Object 



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# File 'lib/fluent/root_agent.rb', line 278

def handle_emits_error(tag, es, error)
  error_info = {error: error, tag: tag}
  if @error_collector
    log.warn "send an error event stream to @ERROR:", error_info
    @error_collector.emit_stream(tag, es)
  else
    now = Time.now
    if @suppress_emit_error_log_interval.zero? || now > @next_emit_error_log_time
      log.warn "emit transaction failed:", error_info
      log.warn_backtrace
      @next_emit_error_log_time = now + @suppress_emit_error_log_interval
    end
    raise error
  end
end

#lifecycle(desc: false, kind_callback: nil) ⇒ Object 



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# File 'lib/fluent/root_agent.rb', line 107

def lifecycle(desc: false, kind_callback: nil)
  kind_or_label_list = if desc
                [:output, :filter, @labels.values.reverse, :output_with_router, :input].flatten
              else
                [:input, :output_with_router, @labels.values, :filter, :output].flatten
              end
  kind_or_label_list.each do |kind|
    if kind.respond_to?(:lifecycle)
      label = kind
      label.lifecycle(desc: desc) do |plugin, display_kind|
        yield plugin, display_kind
      end
    else
      list = if desc
               lifecycle_control_list[kind].reverse
             else
               lifecycle_control_list[kind]
             end
      display_kind = (kind == :output_with_router ? :output : kind)
      list.each do |instance|
        yield instance, display_kind
      end
    end
    if kind_callback
      kind_callback.call
    end
  end
end

#setup_error_label(e) ⇒ Object 



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# File 'lib/fluent/root_agent.rb', line 100

def setup_error_label(e)
  error_label = add_label(ERROR_LABEL)
  error_label.configure(e)
  error_label.root_agent = RootAgentProxyWithoutErrorCollector.new(self)
  @error_collector = error_label.event_router
end

#shutdown ⇒ Object

Fluentd’s shutdown sequence is stop, before_shutdown, shutdown, after_shutdown, close, terminate for plugins



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# File 'lib/fluent/root_agent.rb', line 169

def shutdown # Fluentd's shutdown sequence is stop, before_shutdown, shutdown, after_shutdown, close, terminate for plugins
  # These method callers does `rescue Exception` to call methods of shutdown sequence as far as possible
  # if plugin methods does something like infinite recursive call, `exit`, unregistering signal handlers or others.
  # Plugins should be separated and be in sandbox to protect data in each plugins/buffers.

  lifecycle_safe_sequence = ->(method, checker) {
    lifecycle do |instance, kind|
      begin
        log.debug "calling #{method} on #{kind} plugin", type: Plugin.lookup_type_from_class(instance.class), plugin_id: instance.plugin_id
        instance.send(method) unless instance.send(checker)
      rescue Exception => e
        log.warn "unexpected error while calling #{method} on #{kind} plugin", plugin: instance.class, plugin_id: instance.plugin_id, error: e
        log.warn_backtrace
      end
    end
  }

  lifecycle_unsafe_sequence = ->(method, checker) {
    operation = case method
                when :before_shutdown then "preparing shutdown"
                when :shutdown then "shutting down"
                when :close    then "closing"
                else
                  raise "BUG: unknown method name '#{method}'"
                end
    operation_threads = []
    callback = ->(){
      operation_threads.each{|t| t.join }
      operation_threads.clear
    }
    lifecycle(kind_callback: callback) do |instance, kind|
      t = Thread.new do
        Thread.current.abort_on_exception = true
        begin
          if method == :shutdown
            log.info "#{operation} #{kind} plugin", type: Plugin.lookup_type_from_class(instance.class), plugin_id: instance.plugin_id
          else
            log.debug "#{operation} #{kind} plugin", type: Plugin.lookup_type_from_class(instance.class), plugin_id: instance.plugin_id
          end
          instance.send(method) unless instance.send(checker)
        rescue Exception => e
          log.warn "unexpected error while #{operation} on #{kind} plugin", plugin: instance.class, plugin_id: instance.plugin_id, error: e
          log.warn_backtrace
        end
      end
      operation_threads << t
    end
  }

  lifecycle_safe_sequence.call(:stop, :stopped?)

  # before_shutdown does force_flush for output plugins: it should block, so it's unsafe operation
  lifecycle_unsafe_sequence.call(:before_shutdown, :before_shutdown?)

  lifecycle_unsafe_sequence.call(:shutdown, :shutdown?)

  lifecycle_safe_sequence.call(:after_shutdown, :after_shutdown?)

  lifecycle_unsafe_sequence.call(:close, :closed?)

  lifecycle_safe_sequence.call(:terminate, :terminated?)
end

#start ⇒ Object 



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# File 'lib/fluent/root_agent.rb', line 136

def start
  lifecycle(desc: true) do |i| # instance
    i.start unless i.started?
    # Input#start sometimes emits lots of evetns with in_tail/`read_from_head true` case
    # and it causes deadlock for small buffer/queue output. To avoid such problem,
    # buffer related output threads should be run before `Input#start`.
    # This is why after_start should be called immediately after start call.
    # This depends on `desc: true` because calling plugin order of `desc: true` is
    # Output, Filter, Label, Output with Router, then Input.
    i.after_start unless i.after_started?
  end
end

#suppress_interval(interval_time) ⇒ Object 



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# File 'lib/fluent/root_agent.rb', line 232

def suppress_interval(interval_time)
  @suppress_emit_error_log_interval = interval_time
  @next_emit_error_log_time = Time.now.to_i
end