A series of things you can use to benchmark a Rails or Ruby app.
This gem has been tested and is known to work with Rails 3.2+ using Ruby 2.1+. Some commands may work on older versions of Ruby, but not all commands are supported.
For some benchmarks, not all, you'll need to verify you have a working version of curl on your OS:
$ which curl
/usr/bin/curl
$ curl -V
curl 7.37.1 #...
Put this in your gemfile:
gem 'derailed', group: :development
Then run $ bundle install.
While executing your commands you may need to use bundle exec before typing the command.
To use all profiling methods available also add:
gem "stackprof", group: :development
You must be using Ruby 2.1+ to install these libraries. If you're on an older version of Ruby, what are you waiting for?
There are two ways to use benchmark an app. Derailed can either try to boot your web app and run requests against it while benchmarking, or it can statically give you more information about the dependencies that are in your Gemfile. Booting your app will always be more accurate, but if you cannot get your app to run in production locally, you'll still find the static information useful.
This section covers how to get memory information from your Gemfile without having to boot your app.
All commands in this section will begin with $ derailed bundle:
For more information on the relationship between memory and performance please read/watch How Ruby Uses Memory.
Each gem you add to your project can increase your memory at boot. You can get visibility into the total memory used by each gem in your Gemfile by running:
$ derailed bundle:mem
This will load each of your gems in your Gemfile and see how much memory they consume when they are required. For example if you're using the mail gem. The output might look like this
$ derailed bundle:mem
TOP: 54.1836 MiB
mail: 18.9688 MiB
mime/types: 17.4453 MiB
mail/field: 0.4023 MiB
mail/message: 0.3906 MiB
action_view/view_paths: 0.4453 MiB
action_view/base: 0.4336 MiB
Aside: A "MiB", which is the IEEE and IEC symbol for Mebibyte, is 220 bytes / 1024 Kibibytes (which are in turn 1024 bytes).
Here we can see that mail uses 18MiB, with the majority coming from mime/types. You can use this information to prune out large dependencies you don't need. Also if you see a large memory use by a gem that you do need, please open up an issue with that library to let them know (be sure to include reproduction instructions). Hopefully as a community we can identify memory hotspots and reduce their impact. Before we can fix performance problems, we need to know where those problems exist.
By default this task will only return results from the :default and "production" groups. If you want a different group you can run with.
$ derailed bundle:mem development
You can use CUT_OFF=0.3 to only show files that have above a certain memory useage, this can be used to help eliminate noise.
Note: This method won't include files in your own app, only items in your Gemfile. For that you'll need to use derailed exec mem. See below for more info.
To get more info about the objects, using memory_profiler, created when your dependencies are required you can run:
$ derailed bundle:objects
This will output detailed information about objects created while your dependencies are loaded
Measuring objects created by gems in groups [:default, "production"]
Total allocated 433895
Total retained 100556
allocated memory by gem
-----------------------------------
24369241 activesupport-4.2.1
15560550 mime-types-2.4.3
8103432 json-1.8.2
Once you identify a gem that creates a large amout of memory using $ derailed bundle:mem you can pull that gem into it's own Gemfile and run $ derailed bundle:objects to get detailed information about it. This information can be used by contributors and library authors to identify and eliminate object creation hotspots.
By default this task will only return results from the :default and "production" groups. If you want a different group you can run with.
$ derailed bundle:objects development
Note: This method won't include files in your own app, only items in your Gemfile. For that you'll need to use derailed exec objects. See below for more info.
This benchmarking will attempt to boot your Rails app and run benchmarks against it. Unlike the static benchmarking with $ derailed bundle:* these will include information about your specific app. The pro is you'll get more information and potentially identify problems in your app code, the con is that it requires you to be able to boot and run your application in a production environment locally, which for some apps is non-trivial.
You may want to check out mini-profiler, here's a mini-profiler walkthrough. It's great and does slightly different benchmarking than what you'll find here.
Before you want to attempt any dynamic benchmarks, you'll need to boot your app in production mode. We benchmark using production because it is close to your deployed performance. This section is more a collection of tips rather than a de-facto tutorial.
For starters try booting into a console:
$ RAILS_ENV=production rails console
You may get errors, complaining about not being able to connect to the production database. For this, you can either create a local database with the name of your production database, or you can copy the info from your development group to your production groupu in your database.yml.
You may be missing environment variables expected in production such as SECRET_KEY_BASE. For those you can either commit them to your .env file (if you're using one). Or add them directly to the command:
$ SECRET_KEY_BASE=foo RAILS_ENV=production rails console
Once you can boot a console in production, you'll need to be able to boot a server in production
$ RAILS_ENV=production rails server
You may need to disable enforcing SSL or other domain restrictions temporarially. If you do these, don't forget to add them back in before deploying any code (eek!).
You can get information from STDOUT if you're using rails_12factor gem, or from logs/production.log by running
$ tail -f logs/production.log
Once you've fixed all errors and you can run a server in production, you're almost there.
You can run commands against your app by running $ derailed exec. There are sections on setting up Rack and using authenticated requests below. You can see what commands are available by running:
$ derailed exec --help
$ derailed exec perf:allocated_objects # outputs allocated object diff after app is called TEST_COUNT times
$ derailed exec perf:gc # outputs GC::Profiler.report data while app is called TEST_COUNT times
$ derailed exec perf:ips # iterations per second
$ derailed exec perf:mem # show memory usage caused by invoking require per gem
$ derailed exec perf:objects # profiles ruby allocation
$ derailed exec perf:ram_over_time # outputs ram usage over time
$ derailed exec perf:test # hits the url TEST_COUNT times
Instead of going over each command we'll look at common problems and which commands are best used to diagnose them. Later on we'll cover all of the environment variables you can use to configure derailed benchmarks in it's own section.
If your app appears to be leaking ever increasing amounts of memory, you'll want to first verify if it's an actual unbound "leak" or if it's just using more memory than you want. A true memory leak will increase memory use forever, most apps will increase memory use until they hit a "plateau". To diagnose this you can run:
$ derailed exec perf:ram_over_time
This will boot your app and hit it with requests and output the memory to stdout (and a file under ./tmp). It may look like this:
$ derailed exec perf:ram_over_time
Booting: production
Endpoint: "/"
PID: 78675
103.55078125
178.45703125
179.140625
180.3671875
182.1875
182.55859375
# ...
183.65234375
183.26171875
183.62109375
Here we can see that while the memory use is increasing, it levels off around 183 MiB. You'll want to run this task using ever increasing values of TEST_COUNT= for example
$ TEST_COUNT=5000 derailed exec perf:ram_over_time
$ TEST_COUNT=10_000 derailed exec perf:ram_over_time
$ TEST_COUNT=20_000 derailed exec perf:ram_over_time
Adjust your counts appropriately so you can get results in a reasonable amount of time. If your memory never levels off, congrats! You've got a memory leak! I recommend copying and pasting values from the file generated into google docs and graphing it so you can get a better sense of the slope of your line.
If you don't want it to generate a tmp file with results run with SKIP_FILE_WRITE=1.
If you're pretty sure that there's a memory leak, but you can't confirm it using this method. Look at the environment variable options below, you can try hitting a different endpoint etc.
If you've identified a memory leak, or you simply want to see where your memory use is coming from you'll want to use
$ derailed exec perf:objects
This task hits your app and uses memory_profiler to see where objects are created. You'll likely want to run once, then run it with a higher TEST_COUNT so that you can see hotspots where objects are created on EVERY request versus just maybe on the first.
$ TEST_COUNT=10 derailed exec perf:objects
This is an expensive operation, so you likely want to keep the count lowish. Once you've identified a hotspot read how ruby uses memory for some tips on reducing object allocations.
This is is similar to $ derailed bundle:objects however it includes objects created at runtime. It's much more useful for actual production performance debugging, the other is more useful for library authors to debug.
Ruby memory typically goes in one direction, up. If your memory is large when you boot the application it will likely only increase. In addition to debugging memory retained from dependencies obtained while running $ derailed bundle:mem you'll likely want to see how your own files contribute to memory use.
This task does essentially the same thing, however it hits your app with one request to ensure that any last minute require-s have been called. To execute you can run:
$ derailed exec perf:mem
TOP: 54.1836 MiB
mail: 18.9688 MiB
mime/types: 17.4453 MiB
mail/field: 0.4023 MiB
mail/message: 0.3906 MiB
action_view/view_paths: 0.4453 MiB
action_view/base: 0.4336 MiB
You can use CUT_OFF=0.3 to only show files that have above a certain memory useage, this can be used to help eliminate noise.
If your application code is exremely large at boot consider using $ derailed exec perf:objects to debug low level object creation.
Well...aren't they all. If you've already looked into decreasing object allocations, you'll want to look at where your app is spending the most amount of code. Once you know that, you'll know where to spend your time optimising.
One technique is to use a "sampling" stack profiler. This type of profiling looks at what method is being executed at a given interval and records it. At the end of execution it counts all the times a given method was being called and shows you the percent of time spent in each method. This is a very low overhead method to looking into execution time. Ruby 2.1+ has this available in gem form it's called stackprof. As you guessed you can run this with derailed benchmarks, first add it to your gemfile gem "stackprof", group: :development then execute:
$ derailed exec perf:stackprof
==================================
Mode: cpu(1000)
Samples: 16067 (1.07% miss rate)
GC: 2651 (16.50%)
==================================
TOTAL (pct) SAMPLES (pct) FRAME
1293 (8.0%) 1293 (8.0%) block in ActionDispatch::Journey::Formatter#missing_keys
872 (5.4%) 872 (5.4%) block in ActiveSupport::Inflector#apply_inflections
935 (5.8%) 802 (5.0%) ActiveSupport::SafeBuffer#safe_concat
688 (4.3%) 688 (4.3%) Temple::Utils#escape_html
578 (3.6%) 578 (3.6%) ActiveRecord::Attribute#initialize
3541 (22.0%) 401 (2.5%) ActionDispatch::Routing::RouteSet#url_for
346 (2.2%) 346 (2.2%) ActiveSupport::SafeBuffer#initialize
298 (1.9%) 298 (1.9%) ThreadSafe::NonConcurrentCacheBackend#[]
227 (1.4%) 227 (1.4%) block in ActiveRecord::ConnectionAdapters::PostgreSQLAdapter#exec_no_cache
218 (1.4%) 218 (1.4%) NewRelic::Agent::Instrumentation::Event#initialize
1102 (6.9%) 213 (1.3%) ActiveSupport::Inflector#apply_inflections
193 (1.2%) 193 (1.2%) ActionDispatch::Routing::RouteSet::NamedRouteCollection::UrlHelper#deprecate_string_options
173 (1.1%) 173 (1.1%) ActiveSupport::SafeBuffer#html_safe?
308 (1.9%) 171 (1.1%) NewRelic::Agent::Instrumentation::ActionViewSubscriber::RenderEvent#metric_name
159 (1.0%) 159 (1.0%) block in ActiveRecord::Result#hash_rows
358 (2.2%) 153 (1.0%) ActionDispatch::Routing::RouteSet::Generator#initialize
153 (1.0%) 153 (1.0%) ActiveRecord::Type::String#cast_value
192 (1.2%) 143 (0.9%) ActionController::UrlFor#url_options
808 (5.0%) 127 (0.8%) ActiveRecord::LazyAttributeHash#[]
121 (0.8%) 121 (0.8%) PG::Result#values
120 (0.7%) 120 (0.7%) ActionDispatch::Journey::Router::Utils::UriEncoder#escape
2478 (15.4%) 117 (0.7%) ActionDispatch::Journey::Formatter#generate
115 (0.7%) 115 (0.7%) NewRelic::Agent::Instrumentation::EventedSubscriber#event_stack
114 (0.7%) 114 (0.7%) ActiveRecord::Core#init_internals
263 (1.6%) 110 (0.7%) ActiveRecord::Type::Value#type_cast
8520 (53.0%) 102 (0.6%) ActionView::CompiledTemplates#_app_views_repos__repo_html_slim__2939326833298152184_70365772737940
From here you can dig into individual methods.
Micro benchmarks might tell you at the code level how much faster something is, but what about the overall application speed. If you're trying to figure out how effective a performance change is to your application, it is useful to compare it to your existing app performance. To help you with that you can use:
$ derailed exec perf:ips
Endpoint: "/"
Calculating -------------------------------------
ips 1.000 i/100ms
-------------------------------------------------
ips 3.306 (± 0.0%) i/s - 17.000
This will hit an endpoint in your application using benchmark-ips. In "iterations per second" a higher value is always better. You can run your code change several times using this method, and then run your "baseline" codebase (without your changes) to see how it affects your overall performance. You'll want to run and record the results several times (including the std deviation) so you can help eliminate noise. Benchmarking is hard, this technique isn't perfect but it's definetly better than nothing.
If you care you can also run pure benchmark (without ips):
$ derailed exec perf:test
But I wouldn't, benchmark-ips is a better measure.
All the tasks accept configuration in the form of environment variables.
For tasks that are run a number of times you can set the number using TEST_COUNT for example:
$ derailed exec perf:test TEST_COUNT=100_000
By default tasks will hit your homepage /. If you want to hit a different url use PATH_TO_HIT for example if you wanted to go to users/new you can execute:
$ PATH_TO_HIT=/users/new derailed exec perf:mem
All tests are run without a webserver (directly using Rack::Mock by default), if you want to use a webserver set USE_SERVER to a Rack::Server compliant server, such as webrick.
$ USE_SERVER=webrick derailed exec perf:mem
Or
$ USE_SERVER=puma derailed exec perf:mem
This boots a webserver and hits it using curl instead of in memory. This is useful if you think the performance issue is related to your webserver.
Note: this plugs in the given webserver directly into rack, it doesn't use any puma.config file etc. that you have set-up. If you want to do this, i'm open to suggestions on how (and pull requests)
Tests run against the production environment by default, but it's easy to
change this if your app doesn't run locally with RAILS_ENV set to
production. For example:
$ derailed exec perf:mem RAILS_ENV=development
If you want to customize derailed, you'll need to create a perf.rake file at the root of the directory you're trying to benchmark.
It is possible to run benchmarks directly using rake
$ cat << EOF > perf.rake
require 'bundler'
Bundler.setup
require 'derailed_benchmarks'
require 'derailed_benchmarks/tasks'
EOF
The file should look like this:
$ cat perf.rake
require 'bundler'
Bundler.setup
require 'derailed_benchmarks'
require 'derailed_benchmarks/tasks'
This is done so the benchmarks will be loaded before your application, this is important for some benchmarks and less for others. This also prevents you from accidentally loading these benchmarks when you don't need them.
Then you can execute your commands via rake.
To find out the tasks available you can use $ rake -f perf.rake -T which essentially says use the file perf.rake and list all the tasks.
$ rake -f perf.rake -T
Using Rails? You don't need to do anything special. If you're using Rack, you need to tell us how to boot your app. In your perf.rake file add a task:
namespace :perf do
task :rack_load do
DERAILED_APP = # your code here
end
end
Set the constant DERAILED_APP to your Rack app. See schneems/derailed_benchmarks#1 for more info.
If you're trying to test an endpoint that has authentication you'll need to tell your task how to bypass that authentication. Authentication is controlled by the DerailedBenchmarks.auth object. There is a built in support for Devise. If you're using some other authentication method, you can write your own authentication strategy.
To enable authentication in a test run with:
$ USE_AUTH=true derailed exec perf:mem
See below how to customize authentication.
If you're using devise, there is a built in auth helper that will detect the presence of the devise gem and load automatically.
Create a perf.rake file at your root.
$ cat perf.rake
If you want you can customize the user that is logged in by setting that value in your perf.rake file.
DerailedBenchmarks.auth.user = User.find_or_create!(twitter: "schneems")
You will need to provide a valid user, so depending on the validations you have in your user.rb, you may need to provide different parameters.
If you're trying to authenticate a non-user model, you'll need to write your own custom auth strategy.
To implement your own authentication strategy You will need to create a class that inherits from auth_helper.rb. You will need to implement a setup and a call method. You can see an example of how the devise auth helper was written. You can put this code in your perf.rake file.
class MyCustomAuth < DerailedBenchmarks::AuthHelper
def setup
# initialize code here
end
def call(env)
# log something in on each request
app.call(env)
end
endThe devise strategy works by enabling test mode inside of the Rack request and inserting a stub user. You'll need to duplicate that logic for your own authentication scheme if you're not using devise.
Once you have your class, you'll need to set DerailedBenchmarks.auth to a new instance of your class. In your perf.rake file add:
DerailedBenchmarks.auth = MyCustomAuth.newNow on every request that is made with the USE_AUTH environment variable set, the MyCustomAuth#call method will be invoked.
MIT
Most of the commands are wrappers around other libraries, go check them out. Also thanks to @tenderlove as I cribbed some of the Rails init code in $ rake perf:setup from one of his projects.
kthksbye @schneems