Merge branch 'benchmark-suite' into 'master'

Basic RSpec/benchmark-ips powered benchmark suite

Corresponding issue: #2909, see the commit messages for more details.

A few things to note:

1. The current use of `subject` isn't exactly easy on the eyes due to them having to return a Proc, I'm not sure yet how (and if) we can work around this.
2. The maximum amount of iterations in the current `User.by_login` benchmark is arbitrary, we might have to adjust it once said method's performance has been improved.
3. Benchmarks currently take 2 seconds to warm up and 5 seconds to run (benchmark-ips defaults). 
4. The custom RSpec matcher file (`benchmark_matchers.rb`) is a bit messy, any feedback on this would be appreciated

Any comments/feedback on this would be greatly appreciated.

See merge request !1503

4 files changed, 105 insertions, 3 deletions

diff --git a/spec/benchmarks/models/user_spec.rb b/spec/benchmarks/models/user_spec.rb
new file mode 100644
index 00000000000..168be20b7a5
--- /dev/null
+++ b/spec/benchmarks/models/user_spec.rb
@@ -0,0 +1,40 @@
+require 'spec_helper'
+
+describe User, benchmark: true do
+  describe '.by_login' do
+    before do
+      %w{Alice Bob Eve}.each do |name|
+        create(:user,
+               email: "#{name}@gitlab.com",
+               username: name,
+               name: name)
+      end
+    end
+
+    let(:iterations) { 1000 }
+
+    describe 'using a capitalized username' do
+      benchmark_subject { User.by_login('Alice') }
+
+      it { is_expected.to iterate_per_second(iterations) }
+    end
+
+    describe 'using a lowercase username' do
+      benchmark_subject { User.by_login('alice') }
+
+      it { is_expected.to iterate_per_second(iterations) }
+    end
+
+    describe 'using a capitalized Email address' do
+      benchmark_subject { User.by_login('Alice@gitlab.com') }
+
+      it { is_expected.to iterate_per_second(iterations) }
+    end
+
+    describe 'using a lowercase Email address' do
+      benchmark_subject { User.by_login('alice@gitlab.com') }
+
+      it { is_expected.to iterate_per_second(iterations) }
+    end
+  end
+end
diff --git a/spec/spec_helper.rb b/spec/spec_helper.rb
index dfe855926c6..05bb32baa90 100644
--- a/spec/spec_helper.rb
+++ b/spec/spec_helper.rb
@@ -14,6 +14,7 @@ require File.expand_path("../../config/environment", __FILE__)
 require 'rspec/rails'
 require 'shoulda/matchers'
 require 'sidekiq/testing/inline'
+require 'benchmark/ips'
 
 # Requires supporting ruby files with custom matchers and macros, etc,
 # in spec/support/ and its subdirectories.
@@ -32,7 +33,7 @@ RSpec.configure do |config|
   config.include TestEnv
   config.include StubGitlabCalls
   config.include StubGitlabData
-
+  config.include BenchmarkMatchers, benchmark: true
 
   config.infer_spec_type_from_file_location!
   config.raise_errors_for_deprecations!
diff --git a/spec/support/matchers/benchmark_matchers.rb b/spec/support/matchers/benchmark_matchers.rb
new file mode 100644
index 00000000000..b73a53917f0
--- /dev/null
+++ b/spec/support/matchers/benchmark_matchers.rb
@@ -0,0 +1,59 @@
+module BenchmarkMatchers
+  extend RSpec::Matchers::DSL
+
+  def self.included(into)
+    into.extend(ClassMethods)
+  end
+
+  matcher :iterate_per_second do |min_iterations|
+    supports_block_expectations
+
+    match do |block|
+      @max_stddev ||= 30
+
+      @entry = benchmark(&block)
+
+      expect(@entry.ips).to be >= min_iterations
+      expect(@entry.stddev_percentage).to be <= @max_stddev
+    end
+
+    chain :with_maximum_stddev do |value|
+      @max_stddev = value
+    end
+
+    description do
+      "run at least #{min_iterations} iterations per second"
+    end
+
+    failure_message do
+      ips    = @entry.ips.round(2)
+      stddev = @entry.stddev_percentage.round(2)
+
+      "expected at least #{min_iterations} iterations per second " \
+        "with a maximum stddev of #{@max_stddev}%, instead of " \
+        "#{ips} iterations per second with a stddev of #{stddev}%"
+    end
+  end
+
+  # Benchmarks the given block and returns a Benchmark::IPS::Report::Entry.
+  def benchmark(&block)
+    report = Benchmark.ips(quiet: true) do |bench|
+      bench.report(&block)
+    end
+
+    report.entries[0]
+  end
+
+  module ClassMethods
+    # Wraps around rspec's subject method so you can write:
+    #
+    #     benchmark_subject { SomeClass.some_method }
+    #
+    # instead of:
+    #
+    #     subject { -> { SomeClass.some_method } }
+    def benchmark_subject(&block)
+      subject { block }
+    end
+  end
+end
diff --git a/spec/support/setup_builds_storage.rb b/spec/support/setup_builds_storage.rb
index a3e59646187..a4f21e95338 100644
--- a/spec/support/setup_builds_storage.rb
+++ b/spec/support/setup_builds_storage.rb
@@ -10,8 +10,10 @@ RSpec.configure do |config|
   end
 
   config.after(:suite) do
-    Dir.chdir(builds_path) do
-      `ls | grep -v .gitkeep | xargs rm -r`
+    Dir[File.join(builds_path, '*')].each do |path|
+      next if File.basename(path) == '.gitkeep'
+
+      FileUtils.rm_rf(path)
     end
   end
 end