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Facepalm to Foolproof
Avoiding Common Production Pitfalls
Jon McCartie
@jmccartie
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Hi there! ! I’m Jon McCartie.
I work at Heroku. I help people fix things.
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AirlessBNB
Vacation Rentals In Outer Space
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$ ab -c 100 -n 500 http://airlessbnb.com/
Requests per second: 41.53 [#/sec] (mean)
Time per request: 2407.916 [ms] (mean)
Time per request: 24.079 [ms]
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$ rails server -e production
=> Booting WEBrick
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# Gemfile
gem 'puma'
# Procfile
web: bundle exec puma -C config/puma.rb
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$ ab -c 100 -n 500 http://airlessbnb.com/
Requests per second: 41.53 [#/sec] (mean)
Time per request: 2407.916 [ms] (mean)
Time per request: 24.079 [ms]
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$ ab -c 100 -n 500 http://airlessbnb.com/
Requests per second: 82.94 [#/sec] (mean)
Time per request: 1205.721 [ms] (mean)
Time per request: 12.057 [ms]
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?
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Memory Enemies
1. Memory leaks
- https:/
/github.com/schneems/derailed_benchmarks
- https:/
/blog.codeship.com/debugging-a-memory-leak-on-heroku/
2. Too many web processes
- how much memory does your app consume in one web worker?
- how much memory do you have?
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$ free -m
total used free
Mem: 8014 7528 486
-/+ buffers/cache: 2446 5567
Swap: 511 7 504
Watch Your Memory Usage
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$ free -m
total used free
Mem: 8014 7528 486
-/+ buffers/cache: 2446 5567
Swap: 511 7 504
Watch Your Memory Usage
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$ free -m
total used free
Mem: 8014 7528 486
-/+ buffers/cache: 2446 5567
Swap: 511 7 504
Watch Your Memory Usage
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$ free -m
total used free
Mem: 8014 7528 486
-/+ buffers/cache: 2446 5567
Swap: 511 7 504
Watch Your Memory Usage
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➡
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http:/
/airlessbnb.com/checkout
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# config/production.rb
config.force_ssl = true
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server {
listen 80;
return 301 https://$host$request_uri;
}
nginx.conf
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=> ☄
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404 - Not Found
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# this
/app/assets/images/logo.png
# becomes this
/public/assets/logo-a2c31b21374497ad4db1.png
The Asset Pipeline
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# Nope
# Yup
<%= image_tag "logo.png" %>
# Yup
<%= image_tag "logo.png" %>
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# Nope
.logo
background-image: url("/assets/logo.png")
# Yup
.logo
background-image: image-url("logo.png")
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# config/initializers/assets.rb
Rails.application.config.assets.precompile +=
%w( ads.js ads.css)
Precompile List
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"Is this happening a lot?"
Uhhh… maybe?
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"But Rails already logs to production.log"
But we have multiple machines…
How large is that single production.log file?
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Logging
A twelve-factor app never concerns itself with routing or
storage of its output stream. It should not attempt to write
to or manage logfiles. Instead, each running process writes its
event stream, unbuffered, to stdout.
http:/
/12factor.net/
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# config/environment.rb
config.logger = Logger.new(STDOUT)
Logging
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$ ./bin/stop-production && \
sleep 4 && \
bundle exec ./bin/start-production
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$ mina deploy
-----> Creating the build path
-----> Cloning the Git repository
-----> Installing gem dependencies using Bundler
-----> Moving to releases/4
-----> Symlinking to current
-----> Launching
-----> Done. Deployed v4
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$ heroku create sushi
Creating sushi... done
$ git push heroku master
----> Heroku receiving push
----> Rails app detected
----> Compiled slug size is 8.0MB
sushi.herokuapp.com deployed to heroku
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=>
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$ cat config/s3.yml
production:
bucket: airlessbnb_production
access_key_id: d6bb03e1e761d
secret_access_key: 8921377d4ab6da9
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# config/secrets.yml (.gitignore!)
development:
some_api_key: SOMEKEY
# Usage
Rails.application.secrets.some_api_key
Storing Credentials
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# Gemfile
gem "dotenv-rails"
# .env (.gitignore!)
SECRET_KEY=foo
# on heroku
heroku config:add SECRET_KEY=foo
Environment Variables
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# in your app
ENV["foo"]
# example
REDIS = Redis.new(ENV["REDIS_URL"])
Environment Variables
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# Small App (5,761 records)
User Load (2.3ms) SELECT "users".* FROM "users" WHERE
"users"."username" = "jmccartie"
# Large App (231,138 records)
User Load (51.7ms) SELECT "users".* FROM "users" WHERE
"users"."username" = "jmccartie"
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# Small App (5,761 records)
User Load (2.3ms) SELECT "users".* FROM "users" WHERE
"users"."username" = "jmccartie"
# Large App (231,138 records)
User Load (51.7ms) SELECT "users".* FROM "users" WHERE
"users"."username" = "jmccartie"
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# Small App (5,761 records)
User Load (2.3ms) SELECT "users".* FROM "users" WHERE
"users"."username" = "jmccartie"
# Large App (231,138 records)
User Load (51.7ms) SELECT "users".* FROM "users" WHERE
"users"."username" = "jmccartie"
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class AddIndexForUsernameOnUsers < ActiveRecord::Migration
def change
add_index :users, :username
end
end
Database Indexes
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# Before
User Load (51.7ms) SELECT "users".* FROM "users"
WHERE "users"."username" = "jmccartie"
# After
User Load (1.0ms) SELECT "users".* FROM "users"
WHERE "users"."username" = "jmccartie"
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# Before
User Load (51.7ms) SELECT "users".* FROM "users"
WHERE "users"."username" = "jmccartie"
# After
User Load (1.0ms) SELECT "users".* FROM "users"
WHERE "users"."username" = "jmccartie"
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# Problem
SELECT * FROM users
WHERE thing = 'something'
AND other_thing = 'something_else'
# Solution
add_index :users, [:thing, :other_thing]
Composite Indexes
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Intermission
Just two more chapters in our story…
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So close…
I can feel that $1B valuation just around the corner…
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# photos_controller.rb
@photos = Photo.order(:name)
# index.slim
- @photos do |photo|
= image_tag photo.url
p= photo.user.username
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Photo Load (0.2ms) SELECT "photos".* FROM "photos" ORDER BY name
User Load (0.2ms) SELECT "users".* FROM "users" WHERE "users"."id" = 3
User Load (0.2ms) SELECT "users".* FROM "users" WHERE "users"."id" = 1
User Load (0.2ms) SELECT "users".* FROM "users" WHERE "users"."id" = 5
User Load (0.2ms) SELECT "users".* FROM "users" WHERE "users"."id" = 4
User Load (0.3ms) SELECT "users".* FROM "users" WHERE "users"."id" = 6
User Load (0.3ms) SELECT "users".* FROM "users" WHERE "users"."id" = 7
User Load (0.3ms) SELECT "users".* FROM "users" WHERE "users"."id" = 8
User Load (0.3ms) SELECT "users".* FROM "users" WHERE "users"."id" = 9
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N+1
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# nope
@photos = Photo.all
# yup
@photos = Photo.includes(:user)
N+1 Queries
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# Old
Photo Load (0.2ms) SELECT "photos".* FROM "photos" ORDER BY name
User Load (0.2ms) SELECT "users".* FROM "users" WHERE "users"."id" = 3
User Load (0.2ms) SELECT "users".* FROM "users" WHERE "users"."id" = 1
User Load (0.2ms) SELECT "users".* FROM "users" WHERE "users"."id" = 5
User Load (0.2ms) SELECT "users".* FROM "users" WHERE "users"."id" = 4
User Load (0.3ms) SELECT "users".* FROM "users" WHERE "users"."id" = 2
N+1 Queries
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# New
Photo Load (0.2ms) SELECT "photos".* FROM "photos" LIMIT 0, 30
User Load (0.4ms) SELECT "users".* FROM "users" WHERE
"users"."id" IN (3, 1, 5, 4, 2)
N+1 Queries
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# Gemfile
gem 'bullet', group: :development
N+1 Queries
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# Logs
2016-04-25 20:40:17[INFO] N+1 Query: PATH_INFO: /
photos; model: Photo => associations: [users]·
Add to your finder: :include => [:users]
N+1 Queries
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Request
Controller
Response
S3
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SMS
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@user.send_sms!(message)
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Request
Controller
Response
SMS
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Background Workers
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@user.send_sms!(message)
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SendSmsJob.perform_later(@user, message)
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Request
Controller
Response
SMS
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Request
Controller
Response
SMS
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class SendSmsJob < ActiveJob::Base
queue_as :default
def perform(user, message)
SmsProvider.send(user.phone, message)
end
end
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❤
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Running Your App In Production
Keep learning
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Thank you!
Jon McCartie
@jmccartie
bit.ly/railsconf16
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Heroku Office Hours
Tomorrow, 4:10pm
Heroku Booth
Heroku + Rails Core Team
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