handle error with error handler in async scheduler (#248)

Author: oakbani

lib/optimizely/config_manager/async_scheduler.rb

@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 #
-#    Copyright 2019, Optimizely and contributors
+#    Copyright 2019-2020, Optimizely and contributors
 #
 #    Licensed under the Apache License, Version 2.0 (the "License");
 #    you may not use this file except in compliance with the License.
@@ -19,20 +19,22 @@ module Optimizely
   class AsyncScheduler
     attr_reader :running
 
-    def initialize(callback, interval, auto_update, logger = nil)
+    def initialize(callback, interval, auto_update, logger = nil, error_handler = nil)
       # Sets up AsyncScheduler to execute a callback periodically.
       #
       # callback - Main function to be executed periodically.
       # interval - How many seconds to wait between executions.
       # auto_update - boolean indicates to run infinitely or only once.
       # logger - Optional Provides a logger instance.
+      # error_handler - Optional Provides a handle_error method to handle exceptions.
 
       @callback = callback
       @interval = interval
       @auto_update = auto_update
       @running = false
       @thread = nil
       @logger = logger || NoOpLogger.new
+      @error_handler = error_handler || NoOpErrorHandler.new
     end
 
     def start!
@@ -54,6 +56,7 @@ def start!
           Logger::ERROR,
           "Couldn't create a new thread for async scheduler. #{e.message}"
         )
+        @error_handler.handle_error(e)
       end
     end
 
@@ -80,6 +83,7 @@ def execution_wrapper(callback)
             Logger::ERROR,
             "Something went wrong when executing passed callback. #{e.message}"
           )
+          @error_handler.handle_error(e)
           stop!
         end
         break unless @auto_update

spec/config_manager/async_scheduler_spec.rb

@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 #
-#    Copyright 2019, Optimizely and contributors
+#    Copyright 2019-2020, Optimizely and contributors
 #
 #    Licensed under the Apache License, Version 2.0 (the "License");
 #    you may not use this file except in compliance with the License.
@@ -17,21 +17,36 @@
 #
 require 'spec_helper'
 require 'optimizely/config_manager/async_scheduler'
+require 'optimizely/error_handler'
 require 'optimizely/logger'
 
 describe Optimizely::AsyncScheduler do
+  let(:error_handler) { Optimizely::RaiseErrorHandler.new }
+  let(:spy_logger) { spy('logger') }
+
   it 'should log error trace when callback fails to execute' do
+    allow(Thread).to receive(:new).and_yield
     def some_callback(_args); end
 
-    spy_logger = spy('logger')
-
-    scheduler = Optimizely::AsyncScheduler.new(method(:some_callback), 10, false, spy_logger)
-    scheduler.start!
+    scheduler = Optimizely::AsyncScheduler.new(method(:some_callback), 10, false, spy_logger, error_handler)
 
-    while scheduler.running; end
+    expect { scheduler.start! }.to raise_error(StandardError)
     expect(spy_logger).to have_received(:log).with(
       Logger::ERROR,
       'Something went wrong when executing passed callback. wrong number of arguments (given 0, expected 1)'
     )
   end
+
+  it 'should log error trace when new thread creation fails' do
+    allow(Thread).to receive(:new).and_raise
+    def some_callback(_args); end
+
+    scheduler = Optimizely::AsyncScheduler.new(method(:some_callback), 10, false, spy_logger, error_handler)
+
+    expect { scheduler.start! }.to raise_error(StandardError)
+    expect(spy_logger).to have_received(:log).with(
+      Logger::ERROR,
+      "Couldn't create a new thread for async scheduler. "
+    )
+  end
 end