Implement optional backtrace storage [#155]

Changes.md

@@ -1,6 +1,16 @@
 1.2.0
 -----------
 
+- Error backtraces can optionally be stored as part of the retry,
+  for display in the web UI if you aren't using an error service. [#155]
+
+```ruby
+class Worker
+  include Sidekiq::Worker
+  sidekiq_options :backtrace => true || 10
+end
+```
+
 - Add Timeout middleware to optionally kill a worker after N seconds,
   just configure like so.  (blackgold9)
 

lib/sidekiq/client.rb

@@ -26,6 +26,7 @@ module Sidekiq
     #   class - the worker class to call, required
     #   args - an array of simple arguments to the perform method, must be JSON-serializable
     #   retry - whether to retry this job if it fails, true or false, default true
+    #   backtrace - whether to save any error backtrace, default false
     #
     # All options must be strings, not symbols.  NB: because we are serializing to JSON, all
     # symbols in 'args' will be converted to strings.
@@ -43,6 +44,10 @@ module Sidekiq
       item['retry'] = !!worker_class.get_sidekiq_options['retry']
       queue = item['queue'] || worker_class.get_sidekiq_options['queue'] || 'default'
 
+      if !item['backtrace'] && worker_class.get_sidekiq_options['backtrace']
+        item['backtrace'] = worker_class.get_sidekiq_options['backtrace']
+      end
+
       if !item['timeout'] && worker_class.get_sidekiq_options['timeout']
         item['timeout'] = worker_class.get_sidekiq_options['timeout']
       end

lib/sidekiq/middleware/server/retry_jobs.rb

@@ -42,6 +42,12 @@ module Sidekiq
             msg['retry_count'] = 0
           end
 
+          if msg['backtrace'] == true
+            msg['error_backtrace'] = e.backtrace
+          elsif msg['backtrace'].to_i != 0
+            msg['error_backtrace'] = e.backtrace[0..msg['backtrace'].to_i]
+          end
+
           if count <= MAX_COUNT
             delay = DELAY.call(count)
             logger.debug { "Failure! Retry #{count} in #{delay} seconds" }

lib/sidekiq/worker.rb

@@ -37,6 +37,8 @@ module Sidekiq
       #   :queue - use a named queue for this Worker, default 'default'
       #   :retry - enable the RetryJobs middleware for this Worker, default *true*
       #   :timeout - timeout the perform method after N seconds, default *nil*
+      #   :backtrace - whether to save any error backtrace in the retry payload to display in web UI,
+      #      can be true, false or an integer number of lines to save, default *false*
       def sidekiq_options(opts={})
         @sidekiq_options = get_sidekiq_options.merge(stringify_keys(opts || {}))
       end

test/test_retry.rb

@@ -25,6 +25,34 @@ class TestRetry < MiniTest::Unit::TestCase
       assert_equal msg, msg2
     end
 
+    it 'saves backtraces' do
+      @redis.expect :zadd, 1, ['retry', String, String]
+      msg = { 'class' => 'Bob', 'args' => [1,2,'foo'], 'retry' => true, 'backtrace' => true }
+      handler = Sidekiq::Middleware::Server::RetryJobs.new
+      c = nil
+      assert_raises RuntimeError do
+        handler.call('', msg, 'default') do
+          c = caller(0); raise "kerblammo!"
+        end
+      end
+      assert msg["error_backtrace"]
+      assert_equal c, msg["error_backtrace"]
+    end
+
+    it 'saves partial backtraces' do
+      @redis.expect :zadd, 1, ['retry', String, String]
+      msg = { 'class' => 'Bob', 'args' => [1,2,'foo'], 'retry' => true, 'backtrace' => 3 }
+      handler = Sidekiq::Middleware::Server::RetryJobs.new
+      c = nil
+      assert_raises RuntimeError do
+        handler.call('', msg, 'default') do
+          c = caller(0)[0..3]; raise "kerblammo!"
+        end
+      end
+      assert msg["error_backtrace"]
+      assert_equal c, msg["error_backtrace"]
+    end
+
     it 'handles a new failed message' do
       @redis.expect :zadd, 1, ['retry', String, String]
       msg = { 'class' => 'Bob', 'args' => [1,2,'foo'], 'retry' => true }
@@ -38,6 +66,7 @@ class TestRetry < MiniTest::Unit::TestCase
       assert_equal 'kerblammo!', msg["error_message"]
       assert_equal 'RuntimeError', msg["error_class"]
       assert_equal 0, msg["retry_count"]
+      refute msg["error_backtrace"]
       assert msg["failed_at"]
       @redis.verify
     end

web/views/retry.slim

@@ -23,6 +23,10 @@ header
       tr
         th Error Message
         td= msg['error_message']
+      - if !msg['error_backtrace'].nil?
+        tr
+          th Error Backtrace
+          td== msg['error_backtrace'].join("<br/>")
       - if msg['retry_count'] > 0
         tr
           th Retry Count