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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 -t 5:5 -p ${PORT:-3000} -e ${RACK_ENV:-development}
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$ 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 Rails app consume in one web worker?
- how much memory do you have?
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$ free -m
total used free shared buffers cached
Mem: 8014 7528 486 141 291 4789
-/+ buffers/cache: 2446 5567
Swap: 511 7 504
Watch Your Memory Usage
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$ free -m
total used free shared buffers cached
Mem: 8014 7528 486 141 291 4789
-/+ buffers/cache: 2446 5567
Swap: 511 7 504
Watch Your Memory Usage
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$ free -m
total used free shared buffers cached
Mem: 8014 7528 486 141 291 4789
-/+ buffers/cache: 2446 5567
Swap: 511 7 504
Watch Your Memory Usage
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$ free -m
total used free shared buffers cached
Mem: 8014 7528 486 141 291 4789
-/+ buffers/cache: 2446 5567
Swap: 511 7 504
Watch Your Memory Usage
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=> ☄
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404 - Not Found
The Asset Pipeline
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# this
/app/assets/images/logo.png
# becomes this
/public/assets/logo-a2c31b208b2a62ad9da1374497ad4db1.png
The Asset Pipeline
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# Nope
# Yup
<%= image_tag "logo.png" %>
Your Views
# Yup
<%= image_tag "logo.png" %>
Your Views
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# Nope
.logo
background-image: url("/assets/logo.png")
# Yup
.logo
background-image: image-url("logo.png")
Your CSS
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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
http://sushi.herokuapp.com/ | git@heroku.com:sushi.git
$ git push heroku master
----> Heroku receiving push
----> Rails app detected
----> Compiled slug size is 8.0MB
http://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: d6bb03e1e761dbaebb881e7a8c7a8fcc
secret_access_key: 8921377d4ab6da922f5d8a12fd993ca9
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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
# in your app
ENV["foo"]
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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"
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"
Database Indexes
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Intermission
Just two more chapters in our story…
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Long-running requests consume resources
Off-load to background workers
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# Problem
User.send_sms!(message)
# Solution
SendSmsJob.perform_later(@user, message)
Background Workers
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class SendSmsJob < ActiveJob::Base
queue_as :default
def perform(user, message)
SmsProvider.send(user.phone, message)
end
end
Background Workers
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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
# Logs
2016-02-25 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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Running Your App In Production
Keep learning
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Thank you!
Jon McCartie
@jmccartie
Slides: http:/
/bit.ly/rci2016