Added: Datadog::Worker and extensions.

lib/ddtrace/worker.rb

@@ -0,0 +1,20 @@
+module Datadog
+  # Base class for work tasks
+  class Worker
+    attr_reader \
+      :task
+
+    def initialize(&block)
+      @task = block
+    end
+
+    def perform(*args)
+      task.call(*args) unless task.nil?
+    end
+
+    protected
+
+    attr_writer \
+      :task
+  end
+end

lib/ddtrace/workers/async.rb

@@ -0,0 +1,163 @@
+require 'ddtrace/logger'
+
+module Datadog
+  module Workers
+    module Async
+      # Adds threading behavior to workers
+      # to run tasks asynchronously.
+      # rubocop:disable Metrics/ModuleLength
+      module Thread
+        FORK_POLICY_STOP = :stop
+        FORK_POLICY_RESTART = :restart
+        SHUTDOWN_TIMEOUT = 1
+
+        def self.included(base)
+          base.send(:prepend, PrependedMethods)
+        end
+
+        # Methods that must be prepended
+        module PrependedMethods
+          def perform(*args)
+            start { self.result = super(*args) } if unstarted?
+          end
+        end
+
+        attr_reader \
+          :error,
+          :result
+
+        attr_writer \
+          :fork_policy
+
+        def join(timeout = nil)
+          return true unless running?
+          !worker.join(timeout).nil?
+        end
+
+        def terminate
+          return false unless running?
+          @run_async = false
+          worker.terminate
+          true
+        end
+
+        def run_async?
+          @run_async = false unless instance_variable_defined?(:@run_async)
+          @run_async == true
+        end
+
+        def unstarted?
+          worker.nil? || forked?
+        end
+
+        def running?
+          !worker.nil? && worker.alive?
+        end
+
+        def error?
+          @error = nil unless instance_variable_defined?(:@error)
+          !@error.nil?
+        end
+
+        def completed?
+          !worker.nil? && worker.status == false && !error?
+        end
+
+        def failed?
+          !worker.nil? && worker.status == false && error?
+        end
+
+        def forked?
+          !pid.nil? && pid != Process.pid
+        end
+
+        def fork_policy
+          @fork_policy ||= FORK_POLICY_STOP
+        end
+
+        protected
+
+        attr_writer \
+          :result
+
+        def mutex
+          @mutex ||= Mutex.new
+        end
+
+        def after_fork
+          # Do nothing by default
+        end
+
+        private
+
+        attr_reader \
+          :pid
+
+        def mutex_after_fork
+          @mutex_after_fork ||= Mutex.new
+        end
+
+        def worker
+          @worker ||= nil
+        end
+
+        def start(&block)
+          mutex.synchronize do
+            return if running?
+            if forked?
+              case fork_policy
+              when FORK_POLICY_STOP
+                stop_fork
+              when FORK_POLICY_RESTART
+                restart_after_fork(&block)
+              end
+            elsif !run_async?
+              start_worker(&block)
+            end
+          end
+        end
+
+        def start_worker
+          @run_async = true
+          @pid = Process.pid
+          @error = nil
+          Logger.log.debug("Starting thread in the process: #{Process.pid}")
+
+          @worker = ::Thread.new do
+            begin
+              yield
+            rescue StandardError => e
+              @error = e
+              Logger.log.debug("Worker thread error. Cause #{e.message} Location: #{e.backtrace.first}")
+            end
+          end
+        end
+
+        def stop_fork
+          mutex_after_fork.synchronize do
+            if forked?
+              # Trigger callback to allow workers to reset themselves accordingly
+              after_fork
+
+              # Reset and turn off
+              @pid = Process.pid
+              @run_async = false
+            end
+          end
+        end
+
+        def restart_after_fork(&block)
+          mutex_after_fork.synchronize do
+            if forked?
+              # Trigger callback to allow workers to reset themselves accordingly
+              after_fork
+
+              # Start worker
+              start_worker(&block)
+            end
+          end
+        end
+      end
+    end
+  end
+end

lib/ddtrace/workers/loop.rb

@@ -0,0 +1,105 @@
+module Datadog
+  module Workers
+    # Adds looping behavior to workers, with a sleep
+    # interval between each loop.
+    module IntervalLoop
+      BACK_OFF_RATIO = 1.2
+      BACK_OFF_MAX = 5
+      DEFAULT_INTERVAL = 1
+
+      def self.included(base)
+        base.send(:prepend, PrependedMethods)
+      end
+
+      # Methods that must be prepended
+      module PrependedMethods
+        def perform(*args)
+          perform_loop { super(*args) }
+        end
+      end
+
+      def stop_loop
+        mutex.synchronize do
+          return false unless run_loop?
+          @run_loop = false
+          shutdown.signal
+        end
+
+        true
+      end
+
+      def work_pending?
+        run_loop?
+      end
+
+      def run_loop?
+        @run_loop = false unless instance_variable_defined?(:@run_loop)
+        @run_loop == true
+      end
+
+      def loop_default_interval
+        @loop_default_interval ||= DEFAULT_INTERVAL
+      end
+
+      def loop_back_off_ratio
+        @loop_back_off_ratio ||= BACK_OFF_RATIO
+      end
+
+      def loop_back_off_max
+        @loop_back_off_max ||= BACK_OFF_MAX
+      end
+
+      def loop_wait_time
+        @loop_wait_time ||= loop_default_interval
+      end
+
+      def loop_back_off?
+        false
+      end
+
+      def loop_back_off!(amount = nil)
+        @loop_wait_time = amount || [loop_wait_time * BACK_OFF_RATIO, BACK_OFF_MAX].min
+      end
+
+      protected
+
+      attr_writer \
+        :loop_back_off_max,
+        :loop_back_off_ratio,
+        :loop_default_interval
+
+      def mutex
+        @mutex ||= Mutex.new
+      end
+
+      private
+
+      def perform_loop
+        @run_loop = true
+
+        loop do
+          if work_pending?
+            # Run the task
+            yield
+
+            # Reset the wait interval
+            loop_back_off!(loop_default_interval)
+          elsif loop_back_off?
+            # Back off the wait interval a bit
+            loop_back_off!
+          end
+
+          # Wait for an interval, unless shutdown has been signaled.
+          mutex.synchronize do
+            return unless run_loop? || work_pending?
+            shutdown.wait(mutex, loop_wait_time) if run_loop?
+          end
+        end
+      end
+
+      def shutdown
+        @shutdown ||= ConditionVariable.new
+      end
+    end
+  end
+end

lib/ddtrace/workers/polling.rb

@@ -0,0 +1,48 @@
+require 'ddtrace/workers/async'
+require 'ddtrace/workers/loop'
+
+module Datadog
+  module Workers
+    # Adds polling (async looping) behavior to workers
+    module Polling
+      SHUTDOWN_TIMEOUT = 1
+
+      def self.included(base)
+        base.send(:include, Workers::IntervalLoop)
+        base.send(:include, Workers::Async::Thread)
+        base.send(:prepend, PrependedMethods)
+      end
+
+      # Methods that must be prepended
+      module PrependedMethods
+        def perform(*args)
+          super if enabled?
+        end
+      end
+
+      def stop(force_stop = false, timeout = SHUTDOWN_TIMEOUT)
+        if running?
+          # Attempt graceful stop and wait
+          stop_loop
+          graceful = join(timeout)
+
+          # If timeout and force stop...
+          !graceful && force_stop ? terminate : graceful
+        else
+          false
+        end
+      end
+
+      def enabled?
+        @enabled = true unless instance_variable_defined?(:@enabled)
+        @enabled
+      end
+
+      # Allow worker to be started
+      def enabled=(value)
+        # Coerce to boolean
+        @enabled = (value == true)
+      end
+    end
+  end
+end

lib/ddtrace/workers/queue.rb

@@ -0,0 +1,39 @@
+module Datadog
+  module Workers
+    # Adds queue behavior to workers, with a buffer
+    # to which items can be queued then dequeued.
+    module Queue
+      def self.included(base)
+        base.send(:prepend, PrependedMethods)
+      end
+
+      # Methods that must be prepended
+      module PrependedMethods
+        def perform(*args)
+          super(*dequeue) if work_pending?
+        end
+      end
+
+      def buffer
+        @buffer ||= []
+      end
+
+      def enqueue(*args)
+        buffer.push(args)
+      end
+
+      def dequeue
+        buffer.shift
+      end
+
+      def work_pending?
+        !buffer.empty?
+      end
+
+      protected
+
+      attr_writer \
+        :buffer
+    end
+  end
+end