Ruby

This improve the performance in 18 times when the delegated method raises some exception and in 15% for the success case.

Here a benchmark result with a simpler script: (The backtrace have less than 10 items)

require 'delegate' require 'benchmark/ips' class Foo def name 'foo' end def bla raise end end class Bar < DelegateClass(Foo) end bar = Bar.new(Foo.new) Benchmark.ips do |b| b.report('default') { bar.name } b.report('default raising') { bar.bla rescue nil } end 

Before this patch:

$ ruby delegator_test.rb Calculating ------------------------------------- default 42.999k i/100ms default raising 1.456k i/100ms ------------------------------------------------- default 1.232M (± 9.9%) i/s - 6.106M default raising 14.399k (±13.6%) i/s - 71.344k 

With this patch:

$ ruby delegator_test.rb Calculating ------------------------------------- default 49.024k i/100ms default raising 19.308k i/100ms ------------------------------------------------- default 1.484M (± 8.0%) i/s - 7.403M default raising 263.340k (± 8.0%) i/s - 1.313M 

We could expect more performance difference in a huge application since their backtracers are bigger.

This changes the output of the exception from:

delegator_test.rb:18:in `bla': unhandled exception from delegator_test.rb:43:in `<main>' 

To:

delegator_test.rb:18:in `bla': unhandled exception from /opt/ruby/lib/delegate.rb:340:in `block in delegating_block' from delegator_test.rb:43:in `<main>' 

This patch is important because Rails 4.2 use Delegator in some critical paths.

From our production application this backtrace cleaner was one of the top 3 most CPU consuming calls. Here is the output of stackprof.

block (2 levels) in Delegator.delegating_block (/usr/lib/shopify-ruby/2.1.6-shopify2/lib/ruby/2.1.0/delegate.rb:345) samples: 1228 self (5.2%) / 1228 total (5.2%) callers: 1228 ( 100.0%) block in Delegator.delegating_block code: 1228 (5.2%) / 1228 (5.2%) | 345 | $@.delete_if {|t| /\A#{Regexp.quote(__FILE__)}:#{__LINE__-2}:/o =~ t} if $@ | 346 | end 

Given the positive performance impact and that the difference of the backtrace output is not so big, I believe it is worth to consider removing the backtrace cleaner.