Add bin/profile-url tool and docs

bin/profile-url

+#!/usr/bin/env ruby
+require 'optparse'
+
+options = {}
+
+opt_parser = OptionParser.new do |opt|
+  opt.banner = <<DOCSTRING
+Profile a URL on this GitLab instance.
+
+Usage:
+  #{__FILE__} url --output=<profile-html> --sql=<sql-log> [--user=<user>] [--post=<post-data>]
+
+Example:
+  #{__FILE__} /dashboard/issues --output=dashboard-profile.html --sql=dashboard.log --user=root
+DOCSTRING
+  opt.separator ''
+  opt.separator 'Options:'
+
+  opt.on('-o', '--output=/tmp/profile.html', 'profile output filename') do |output|
+    options[:profile_output] = output
+  end
+
+  opt.on('-s', '--sql=/tmp/profile_sql.txt', 'SQL output filename') do |sql|
+    options[:sql_output] = sql
+  end
+
+  opt.on('-u', '--user=root', 'User to authenticate as') do |username|
+    options[:username] = username
+  end
+
+  opt.on('-p', "--post='user=john&pass=test'", 'Send HTTP POST data') do |post_data|
+    options[:post_data] = post_data
+  end
+end
+
+opt_parser.parse!
+options[:url] = ARGV[0]
+
+if options[:url].nil? ||
+   options[:profile_output].nil? ||
+   options[:sql_output].nil?
+  puts opt_parser
+  exit
+end
+
+require File.expand_path('../config/environment', File.dirname(__FILE__))
+
+result = Gitlab::Profiler.profile(options[:url],
+                                  logger: Logger.new(options[:sql_output]),
+                                  post_data: options[:post_data],
+                                  user: User.find_by_username(options[:username]),
+                                  private_token: ENV['PRIVATE_TOKEN'])
+
+printer = RubyProf::CallStackPrinter.new(result)
+file = File.open(options[:profile_output], 'w')
+printer.print(file)
+file.close

doc/development/performance.md

@@ -36,7 +36,8 @@ graphs/dashboards.
 
 GitLab provides built-in tools to aid the process of improving performance:
 
-* [Sherlock](profiling.md#sherlock)
+* [Profiling](profiling.md)
+  * [Sherlock](profiling.md#sherlock)
 * [GitLab Performance Monitoring](../administration/monitoring/performance/index.md)
 * [Request Profiling](../administration/monitoring/performance/request_profiling.md)
 * [QueryRecoder](query_recorder.md) for preventing `N+1` regressions

doc/development/profiling.md

@@ -4,6 +4,41 @@ To make it easier to track down performance problems GitLab comes with a set of
 profiling tools, some of these are available by default while others need to be
 explicitly enabled.
 
+## Profiling a URL
+
+There is a `Gitlab::Profiler.profile` method, and corresponding
+`bin/profile-url` script, that enable profiling a GET or POST request to a
+specific URL, either as an anonymous user (the default) or as a specific user.
+
+When using the script, command-line documentation is available by passing no
+arguments.
+
+When using the method in an interactive console session, any changes to the
+application code within that console session will be reflected in the profiler
+output.
+
+For example:
+
+```ruby
+Gitlab::Profiler.profile('/my-user')
+# Returns a RubyProf::Profile for the regular operation of this request
+class UsersController; def show; sleep 100; end; end
+Gitlab::Profiler.profile('/my-user')
+# Returns a RubyProf::Profile where 100 seconds is spent in UsersController#show
+```
+
+Passing a `logger:` keyword argument to `Gitlab::Profiler.profile` will send
+ActiveRecord and ActionController log output to that logger. Further options are
+documented with the method source.
+
+[GitLab-Profiler](https://gitlab.com/gitlab-com/gitlab-profiler) is a project
+that builds on this to add some additional niceties, such as allowing
+configuration with a single Yaml file for multiple URLs, and uploading of the
+profile and log output to S3.
+
+For GitLab.com, you can find the latest results here:
+<http://redash.gitlab.com/dashboard/gitlab-profiler-statistics>
+
 ## Sherlock
 
 Sherlock is a custom profiling tool built into GitLab. Sherlock is _only_
@@ -27,13 +62,3 @@ Bullet will log query problems to both the Rails log as well as the Chrome
 console.
 
 As a follow up to finding `N+1` queries with Bullet, consider writing a [QueryRecoder test](query_recorder.md) to prevent a regression.
-
-## GitLab Profiler
-
-
-[Gitlab-Profiler](https://gitlab.com/gitlab-com/gitlab-profiler) was built to
-help developers understand why specific URLs of their application may be slow
-and to provide hard data that can help reduce load times.
-
-For GitLab.com, you can find the latest results here:
-<http://redash.gitlab.com/dashboard/gitlab-profiler-statistics>