Containerising Applications For Docker

A presentation by @stuherbert  for @GanbaroDigital Designing Docker Containers For
PHP App Development

Industry veteran: architect, engineer, leader, manager, mentor F/OSS contributor since
1994 Talking and writing about PHP since 2004 Chief Software Archaeologist @GanbaroDigital About Stuart

Follow me I do tweet a lot about non-tech stuff
though :) @stuherbert

@GanbaroDigital This isn’t a “What Is Docker?” talk, nor a
“Why Docker?” talk.

@GanbaroDigital This is more a “How to Dockerize?” talk.

@GanbaroDigital The underlying principles apply to any containerised application.

@GanbaroDigital Why am I giving this talk?

@GanbaroDigital This is a follow-up to my talk Docker for
PHP Dev Environments presented @PHPMinds in 2017

@GanbaroDigital https://speakerdeck.com/stuartherbert/ docker-for-php-dev-environments

@GanbaroDigital I’ve been working with clients who want to Dockerize
everything. The same points come up every time.

@GanbaroDigital Containers are different to virtual machines

@GanbaroDigital Your data if you lift and shift a VM
into a container

@GanbaroDigital “ Some things change, and some things stay the
same.

@GanbaroDigital This is my experience. This is how I do
it, and why.

@GanbaroDigital Other approaches exist. I’m here to learn from you
too!

@GanbaroDigital Please ask questions as we go.

@GanbaroDigital In This Talk ... 1. Common Understanding 2. Image
and Container Properties 3. Putting It All Together 4. Common Questions

@GanbaroDigital Common Understanding

@GanbaroDigital “ Docker’s terminology can be very confusing when you’re
starting out.

@GanbaroDigital ?? ?? What do we mean when we talk
about containers and images?

@GanbaroDigital A Docker image is a blueprint that has been
built.

@GanbaroDigital The blueprint is the Dockerﬁle.

@GanbaroDigital A Docker container is a running instance of a
Docker image.

@GanbaroDigital You can spin up many containers from the same
image.

@GanbaroDigital Image & Container Properties

@GanbaroDigital “ Things are easier when something is used in
the way it was intended.

@GanbaroDigital Image Properties

@GanbaroDigital Image Properties Include ... • Distribution • Layering

@GanbaroDigital https://ﬂic.kr/p/SgsXBV Distribution

@GanbaroDigital An image is a thing that you can distribute.
Just like a VBOX ﬁle.

@GanbaroDigital Docker Hub

@GanbaroDigital You can use the same image in dev, test,
& production to guarantee the same behaviour everywhere.

@GanbaroDigital “ You don’t want the same behaviour in dev,
test & production.

& production to guarantee the same behaviour everywhere.

& production to guarantee the same software everywhere.

@GanbaroDigital ?? ?? What differences do we want?

@GanbaroDigital “Dev images are optimised for developer productivity. Test /
prod images are optimised for production use.

@GanbaroDigital Differences Wanted ... • Logging levels • PHP proﬁler
modules • PHP opcache conﬁg • Baking your app into the image

@GanbaroDigital https://ﬂic.kr/p/FQ4jk9 Layering

@GanbaroDigital Docker images are layered.

@GanbaroDigital

@GanbaroDigital “Docker images are layered. Generalise base layers, specialise later
layers.

@GanbaroDigital Container Properties

@GanbaroDigital Container Properties Include ... • Co-location • Non-persistence •
Customisation • Copy-on-write ﬁlesystem

@GanbaroDigital https://ﬂic.kr/p/94KBK1 Co-location

@GanbaroDigital ?? ?? What can you run inside a Docker
container?

@GanbaroDigital Anything you choose. (Almost)

@GanbaroDigital And as many things as you want.

@GanbaroDigital “ You can co-locate multiple processes inside a single
container.

@GanbaroDigital https://ﬂic.kr/p/ab5xJY Non-persistence

@GanbaroDigital Persistence is the ability to survive the destruction and
re-creation of a Docker container.

@GanbaroDigital It’s normal to destroy Docker containers and then re-create
them from the underlying Docker image.

@GanbaroDigital When you destroy a Docker container, you lose everything
you’ve saved inside that container.

@GanbaroDigital “ The contents of a Docker container are not
persistent.

@GanbaroDigital The contents of a Docker container are not persistent.

into a container

@GanbaroDigital ?? ?? What kinds of persistent data does your
app create?

@GanbaroDigital Persistent Data Includes ... • Databases • File uploads
• Session data • Auto-upgrades / plugin installs (Wordpress) • Logs

@GanbaroDigital We can mount persistent data volumes into containers.

@GanbaroDigital

@GanbaroDigital https://ﬂic.kr/p/j6mk6C Customised

@GanbaroDigital Docker containers can write to their ﬁlesystems.

@GanbaroDigital We can use that to customise conﬁg ﬁles when
a Docker container starts up.

@GanbaroDigital ?? ?? Why might we want to modify conﬁg
ﬁles at startup?

@GanbaroDigital Nginx

@GanbaroDigital “ A one-time startup script can tailor your container.

@GanbaroDigital https://ﬂic.kr/p/64YX6u COW Filesystem

@GanbaroDigital Docker containers use a copy-on-write ﬁlesystem.

@GanbaroDigital Writes are slow, and if you hit them hard
enough, they break.

@GanbaroDigital “ After startup, write as little as possible to
a Docker container’s ﬁlesystem.

@GanbaroDigital 5 Key Design Questions • How can I break
my image up into layers? • What does my app need? • How do I conﬁgure everything? • Where will persistent data go? • How do I avoid all other writes to the FS?

@GanbaroDigital Putting It All Together

@GanbaroDigital https://github.com/ganbarodigital/docker-images/

@GanbaroDigital The Base Image

@GanbaroDigital Base Ubuntu Server

@GanbaroDigital • Your (minimal) operating system of choice • +
anything all your child images regularly need • + convenience tools for when (not if) you shell into the containers • + standardise volume mount points

@GanbaroDigital “Get it right in the base layer. Don’t have
to put it right further up in your image stack.

@GanbaroDigital Supervisord

@GanbaroDigital /etc/supervisor/supervisord.conf

@GanbaroDigital /etc/supervisor/conf.d/nginx.conf

@GanbaroDigital /usr/local/sbin/image-startup.sh

@GanbaroDigital Dockerﬁle: standardise side-load mount points

@GanbaroDigital Web Server

@GanbaroDigital Base Web Server Ubuntu Server Nginx or Apache

@GanbaroDigital • Your web server of choice • + default
conﬁg ﬁles

@GanbaroDigital Nginx default site

@GanbaroDigital Why A Web Server Image? • Standalone use: static
sites • Shared basis: PHP, Python, Ruby, etc etc

@GanbaroDigital Runtime

@GanbaroDigital Base Web Server PHP Ubuntu Server Nginx or Apache
PHP-FPM or mod_php

@GanbaroDigital • This is where your language runtime goes •
+ supporting conﬁg ﬁles

@GanbaroDigital https://ﬂic.kr/p/94KBK1 Co-location Example

@GanbaroDigital “ PHP goes in the same Docker container as
your web server.

@GanbaroDigital ?? ?? What happens if you run Apache/Nginx and
PHP in separate containers?

@GanbaroDigital Physical Server Apache mod_php

@GanbaroDigital Apache + mod_php • mod_php runs inside the Apache
process • You can’t split a single process across two containers

@GanbaroDigital Container Apache mod_php

@GanbaroDigital ?? ?? What about Apache/Nginx + PHP-FPM?

@GanbaroDigital Apache/Nginx and PHP-FPM are separate processes.

@GanbaroDigital We can split separate processes into separate containers. All
the early advice was: 1 process per container

@GanbaroDigital

@GanbaroDigital Physical Server

@GanbaroDigital Apache Physical Server

@GanbaroDigital Apache PHP-FPM Physical Server

@GanbaroDigital ?? ?? How do they talk to each other?

@GanbaroDigital Apache PHP-FPM unix domain socket (very fast) Physical Server

@GanbaroDigital Apache PHP-FPM unix domain socket (very fast) Container #1

@GanbaroDigital Not really any different to Apache/Nginx + PHP-FPM performance
on a physical server.

@GanbaroDigital Apache PHP-FPM unix domain socket (very fast) Container #1

@GanbaroDigital Apache PHP-FPM Container #1 Container #2

@GanbaroDigital ?? ?? How do they talk to each other?

@GanbaroDigital Apache PHP-FPM Virtualised network  (not as fast) Container #1
Container #2

@GanbaroDigital Virtualised network  (not as fast) Container #1 Container #2
Apache PHP-FPM

@GanbaroDigital “ Co-locate all the things that you’d never put
on separate physical servers.

@GanbaroDigital “ Separate all the things that would stop you
scaling horizontally.

@GanbaroDigital This generic PHP image is my dev image.

@GanbaroDigital Base Application  (if applicable)

@GanbaroDigital Base Web Server PHP Wordpress Ubuntu Server Nginx or
Apache PHP-FPM or mod_php Base application

@GanbaroDigital • This layer is optional • Build a vanilla
image for your base app (e.g. Wordpress, Magento) • Add in any common plugins/modules • Use as the base for multiple customisations down the road

@GanbaroDigital Your App

@GanbaroDigital Base Web Server PHP Wordpress Your App Ubuntu Server
Nginx or Apache PHP-FPM or mod_php Base application Proﬁt :)

@GanbaroDigital Final layer is your code.

@GanbaroDigital ?? ?? Can we add more layers?

@GanbaroDigital You could add one more layer, for customer-speciﬁc customisation.

@GanbaroDigital

@GanbaroDigital Common Questions

@GanbaroDigital 3 Common Questions • Databases inside containers • SSH
servers • Port forwarding

@GanbaroDigital ?? ?? Can you run a database server (e.g.
MySQL, MongoDB) inside a container?

@GanbaroDigital Yes. As long as they store all data on
a persistent volume.

@GanbaroDigital Databases do not need to be co-located with your
app. So run them in their own container.

@GanbaroDigital ?? ?? Should you run an SSH server in
each Docker container?

@GanbaroDigital I don’t any more.

@GanbaroDigital • Most of my containers are behind a proxy
or load balancer of some kind. • Can’t reach them from an off-host network. • One less thing to worry about.

@GanbaroDigital A lot of the advice out there is built
around port forwarding. I prefer to run my containers with their own IP addresses.

@GanbaroDigital Summing Up

@GanbaroDigital 5 Key Design Questions • How can I break
my image up into layers? • What does my app need? • How do I conﬁgure everything? • Where will persistent data go? • How do I avoid all other writes to the FS?

@GanbaroDigital “ You don’t want the same behaviour in dev,
test & production.

@GanbaroDigital “Dev images are optimised for developer productivity. Test /
prod images are optimised for production use.

@GanbaroDigital “Docker images are layered. Generalise base layers, specialise later
layers.

@GanbaroDigital “Get it right in the base layer. Don’t have
to put it right further up in your image stack.

@GanbaroDigital “Standardise where things go. /conﬁg /data /logs & /workspace

@GanbaroDigital “ A one-time startup script can tailor your container.

@GanbaroDigital “ After startup, write as little as possible to
a Docker container’s ﬁlesystem.

@GanbaroDigital “ Co-locate all the things that you’d never put
on separate physical servers.

@GanbaroDigital “ Separate all the things that would stop you
scaling horizontally.

@GanbaroDigital “ The contents of a Docker container are not
persistent.

@GanbaroDigital The contents of a Docker container are not persistent.

into a container

@GanbaroDigital https://github.com/ganbarodigital/docker-images/

Thank You Any Questions? A presentation by @stuherbert  for @GanbaroDigital

Containerising Applications For Docker

Containerising Applications For Docker

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