Cloud Foundry
From Zero To Hero

05 How do I make my app resilient?

Feature

As a CF hero
I want my app to be resilient
So that random failures won't take it offline

Let’s ship it

# From the training home directory:
$ cd 05-resilience/imperfect-app
$ cf push

...

urls: imperfect-app-votive-seeress.cfapps.io

...

You’ve shipped your new app!

The static website is handling the traffic wonderfully

Everyone wants to use your new app, but…

It crashes

Version 1 Sucks, But Ship It Anyway

How to make an app resilient?

Embrace failure & run many instances of the same app

$ cf scale imperfect-app -i 3
$ cf apps

name            state     instances   memory   disk   urls
imperfect-app   started   2/3         64M      256M   imperfect..

Many crashed instances,
app still available

$ cf app imperfect-app

     state     since       cpu    memory         disk
#0   running   2015-11-02  0.0%   25.3M of 32M   66.9M of 128M
#1   down      2015-11-02  0.0%   0 of 0         0 of 0
#2   down      2015-11-02  0.0%   0 of 0         0 of 0

$ watch cf apps # Watch app instances restart in real-time

What restarts crashed apps?

Health Manager in DEA v2 (a.k.a. HM9K)

Health Check in Diego v3

My app needs more memory

$ cf events imperfect-app

description
index: 1, reason: CRASHED... Exited with status 255 (out of memory)

$ cf scale imperfect-app -m 256M

My app needs more disk space

Do not use the app’s disk for persistence

$ cf app imperfect-app

     state     since        cpu    memory           disk
#0   running   2015-11-02   0.0%   24.4M  of 256M   95.2M  of 256M
#1   running   2015-11-02   0.0%   112.4M of 256M   224.2M of 256M
#0   running   2015-11-02   0.0%   24.3M  of 256M   95.2M  of 256M

$ cf logs imperfect-app --recent

Errno::EDQUOT - Disk quota exceeded @ io_write - infinite-file:

$ cf scale imperfect-app -k 1G

Scale instances, disk & memory

Combine multiple options in a single command

$ cf help scale

NAME:
   scale - Change or view the instance count, disk space limit...

USAGE:
   cf scale APP_NAME [-i INSTANCES] [-k DISK] [-m MEMORY] [-f]

OPTIONS:
   -i       Number of instances
   -k       Disk limit (e.g. 256M, 1024M, 1G)
   -m       Memory limit (e.g. 256M, 1024M, 1G)
   -f       Force restart of app without prompt

The Twelve-Factor App

DELIVERED

As a CF hero
I want my app to be resilient
So that random failures won't take it offline

Any questions?

Questions cannot be stupid. Answers can.

CF SUPERHERO

Read the Twelve-Factor App
Benchmark app with Load Impact (crash 1-2 instances)
Read about Blue-Green deployment in CF
Use cf-blue-green-deploy cli plugin