Let's Containerize New York with Docker!

Lightweight Virtualization
with

Linux Containers
and

Docker

Outline
●

Why Linux Containers?

●

What are Linux Containers exactly?

●

What do we need on top of LXC?

●

Why Docker?

●

What is Docker exactly?

●

Where is it going?

Why Linux Containers?

What are
we trying
to solve?

The Matrix From Hell
django
web
frontend
node.js
async API
background
workers
SQL
database
distributed
DB, big data
message
queue

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staging

prod on
cloud
VM

my
laptop

your
laptop

QA

prod on bare
metal

Many payloads
●

backend services (API)

●

databases

●

distributed stores

●

webapps

Many payloads
●

Go

●

Java

●

Node.js

●

PHP

●

Python

●

Ruby

●

…

Many payloads
●

CherryPy

●

Django

●

Flask

●

Plone

●

...

Many payloads
●

Apache

●

Gunicorn

●

uWSGI

●

...

Many targets
●

your local development environment

●

your coworkers' developement environment

●

your Q&A team's test environment

●

some random demo/test server

●

the staging server(s)

●

the production server(s)

●

bare metal

●

virtual machines

●

shared hosting

Many targets
●

BSD

●

Linux

●

OS X

●

Windows

Many targets
●

BSD

●

Linux

●

OS X

●

Windows

Not yet

Real-world analogy:
containers

Many products
●

clothes

●

electronics

●

raw materials

●

wine

●

…

Many transportation methods
●

ships

●

trains

●

trucks

●

...

Another matrix from hell
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Solution to the transport problem:
the intermodal shipping container

Solution to the transport problem:
the intermodal shipping container
●

●

●
●

●

90% of all cargo now shipped in a standard
container
faster and cheaper to load and unload on ships
(by an order of magnitude)
less theft, less damage
freight cost used to be >25% of final goods
cost, now <3%
5000 ships deliver 200M containers per year

Solution to the deployment problem:

the Linux container

Linux containers...
Units of software delivery (ship it!)
●

run everywhere
–
–

regardless of host distro

–
●

regardless of kernel version
(but container and host architecture must match*)

run anything
–

if it can run on the host, it can run in the container

–

i.e., if it can run on a Linux kernel, it can run

*Unless you emulate CPU with qemu and binfmt

What are Linux Containers exactly?

High level approach:
it's a lightweight VM
●

own process space

●

own network interface

●

can run stuff as root

●

can have its own /sbin/init
(different from the host)

« Machine Container »

Low level approach:
it's chroot on steroids
●

can also not have its own /sbin/init

●

container = isolated process(es)

●

share kernel with host

●

no device emulation (neither HVM nor PV)

« Application Container »

Separation of concerns:
Dave the Developer
●

inside my container:
–

my code

–

my libraries

–

my package manager

–

my app

–

my data

Separation of concerns:
Oscar the Ops guy
●

outside the container:
–

logging

–

remote access

–

network configuration

–

monitoring

How does it work?
Isolation with namespaces
●

pid

●

mnt

●

net

●

uts

●

ipc

●

user

pid namespace
jpetazzo@tarrasque:~$ ps aux | wc -l
212
jpetazzo@tarrasque:~$ sudo docker run -t
bash
root@ea319b8ac416:/# ps aux
USER
PID %CPU %MEM
VSZ
RSS TTY
STAT
COMMAND
root
1 0.0 0.0 18044 1956 ?
S
bash
root
16 0.0 0.0 15276 1136 ?
R+
ps aux

(That's 2 processes)

-i ubuntu
START

TIME

02:54

0:00

02:55

0:00

mnt namespace
jpetazzo@tarrasque:~$ wc -l
/proc/mounts
32 /proc/mounts

root@ea319b8ac416:/# wc -l
/proc/mounts
10 /proc/mounts

net namespace
root@ea319b8ac416:/# ip addr
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
22: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP>
pfifo_fast state UP qlen 1000

mtu 1500 qdisc

link/ether 2a:d1:4b:7e:bf:b5 brd ff:ff:ff:ff:ff:ff
inet 10.1.1.3/24 brd 10.1.1.255 scope global eth0
inet6 fe80::28d1:4bff:fe7e:bfb5/64 scope link

uts namespace
jpetazzo@tarrasque:~$ hostname
tarrasque
root@ea319b8ac416:/# hostname
ea319b8ac416

ipc namespace
jpetazzo@tarrasque:~$ ipcs
------ Shared Memory Segments -------key
shmid
owner
perms
0x00000000 3178496
jpetazzo
600
0x00000000 557057
jpetazzo
777
0x00000000 3211266
jpetazzo
600

root@ea319b8ac416:/# ipcs
------ Shared Memory Segments -------key
shmid
owner
perms
------ Semaphore Arrays -------key
semid
owner
perms
------ Message Queues -------key
msqid
owner
perms

bytes
393216
2778672
393216

nattch
2
0
2

status
dest

bytes

nattch

status

nsems
used-bytes

messages

dest

user namespace
●
●

no « demo » for this one... Yet!
UID 0→1999 in container C1 is mapped to
UID 10000→11999 in host;
UID 0→1999 in container C2 is mapped to
UID 12000→13999 in host; etc.

●

required lots of VFS and FS patches (esp. XFS)

●

what will happen with copy-on-write?
–

double translation at VFS?

–

single root UID on read-only FS?

How does it work?
Isolation with cgroups
●

memory

●

cpu

●

blkio

●

devices

memory cgroup
●

keeps track pages used by each group:
–

file (read/write/mmap from block devices; swap)

–

anonymous (stack, heap, anonymous mmap)

–

active (recently accessed)

–

inactive (candidate for eviction)

●

each page is « charged » to a group

●

pages can be shared (e.g. if you use any COW FS)

●

Individual (per-cgroup) limits and out-of-memory killer

cpu and cpuset cgroups
●

keep track of user/system CPU time

●

set relative weight per group

●

pin groups to specific CPU(s)
–

Can be used to « reserve » CPUs for some apps

–

This is also relevant for big NUMA systems

blkio cgroups
●

keep track IOs for each block device
–

read vs write; sync vs async

●

set relative weights

●

set throttle (limits) for each block device
–

read vs write; bytes/sec vs operations/sec

Note: earlier versions (pre-3.8) didn't account async
correctly.
3.8 is better, but use 3.10 for best results.

devices cgroups
●

controls read/write/mknod permissions

●

typically:
–

allow: /dev/{tty,zero,random,null}...

–

deny: everything else

–

maybe: /dev/net/tun, /dev/fuse

If you're serious about security,
you also need…
●

capabilities
–

okay: cap_ipc_lock, cap_lease, cap_mknod,
cap_net_admin, cap_net_bind_service, cap_net_raw

–

troublesome: cap_sys_admin (mount!)

●

think twice before granting root

●

grsec is nice

●

seccomp (very specific use cases); seccomp-bpf

●

beware of full-scale kernel exploits!

Efficiency: almost no overhead
●

●

●

●

processes are isolated, but run straight on the
host
CPU performance
= native performance
memory performance
= a few % shaved off for (optional) accounting
network performance
= small overhead; can be optimized to zero
overhead

Efficiency: storage-friendly
●

●

●

unioning filesystems
(AUFS, overlayfs)
snapshotting filesystems
(BTRFS, ZFS)
copy-on-write
(thin snapshots with LVM or device-mapper)

This is now being integrated with low-level LXC tools as well!

Efficiency: storage-friendly
●

provisioning now takes a few milliseconds

●

… and a few kilobytes

●

creating a new base image (from a running
container) takes a few seconds (or even less)

What can Docker do?
●

Open Source engine to commoditize LXC

●

using copy-on-write for quick provisioning

●

allowing to create and share images

●

●

standard format for containers
(stack of layers; 1 layer = tarball+metadata)
standard, reproducible way to easily build
trusted images (Dockerfile, Stackbrew...)

Authoring images
with run/commit
1) docker run ubuntu bash
2) apt-get install this and that
3) docker commit <containerid> <imagename>
4) docker run <imagename> bash
5) git clone git://.../mycode
6) pip install -r requirements.txt
7) docker commit <containerid> <imagename>
8) repeat steps 4-7 as necessary
9) docker tag <imagename> <user/image>
10) docker push <user/image>

Authoring images
with a Dockerfile
FROM ubuntu
RUN
RUN
RUN
RUN
RUN

apt-get
apt-get
apt-get
apt-get
apt-get

-y update
install -y
install -y
install -y
install -y

g++
erlang-dev erlang-manpages erlang-base-hipe ...
libmozjs185-dev libicu-dev libtool ...
make wget

RUN wget http://.../apache-couchdb-1.3.1.tar.gz | tar -C /tmp -zxfRUN cd /tmp/apache-couchdb-* && ./configure && make install
RUN printf "[httpd]nport = 8101nbind_address = 0.0.0.0" >
/usr/local/etc/couchdb/local.d/docker.ini
EXPOSE 8101
CMD ["/usr/local/bin/couchdb"]

docker build -t jpetazzo/couchdb .

Running containers
●

SSH to Docker host and manual pull+run

●

REST API (feel free to add SSL certs, OAUth...)

●

OpenStack Nova

●

OpenStack Heat

●

who's next? OpenShift, CloudFoundry?

●

multiple Open Source PAAS built on Docker
(more on this later)

Yes, but...
●

●

●

« I don't need Docker;
I can do all that stuff with LXC tools, rsync,
some scripts! »
correct on all accounts;
but it's also true for apt, dpkg, rpm, yum, etc.
the whole point is to commoditize,
i.e. make it ridiculously easy to use

What this really means…
●

instead of writing « very small shell scripts » to
manage containers, write them to do the rest:
–

continuous deployment/integration/testing

–

orchestration

●

= use Docker as a building block

●

re-use other people images (yay ecosystem!)

Docker: sharing images
●

●
●

you can push/pull images to/from a registry
(public or private)
you can search images through a public index
dotCloud Docker Inc. the community
maintains a collection of base images
(Ubuntu, Fedora...)

●

coming soon: Stackbrew

●

satisfaction guaranteed or your money back

Docker: not sharing images
●

private registry
–
–

or security credentials

–
●

for proprietary code
or fast local access

the private registry is available
as an image on the public registry
(yes, that makes sense)

Example of powerful workflow
●

●

●

●

code in local environment
(« dockerized » or not)
each push to the git repo triggers a hook
the hook tells a build server to clone the code and run
« docker build » (using the Dockerfile)
the containers are tested (nosetests, Jenkins...),
and if the tests pass, pushed to the registry

●

production servers pull the containers and run them

●

for network services, load balancers are updated

Orchestration (0.6.5)
●
●

●

you can name your containers
they get a generated name by default
(red_ant, gold_monkey...)
you can link your containers

docker run -d -name frontdb
docker run -d -link frontdb:sql frontweb
→ container frontweb gets one bazillion environment vars

Orchestration roadmap
●
●

●

currently single-host
problem:
how do I link with containers on other hosts?
solution:
ambassador pattern!
–

app container runs in its happy place

–

other things (Docker, containers...) plumb it

Orchestration roadmap
●
●

●

currently static
problem:
what if I have to move a container?
what if there is a master/slave failover?
what if I have to WebScale my MangoDB
cluster?
solution:
dynamic discovery using Redis protocol

Dynamic Disco
●

beam
–

introspection API

–

based on Redis protocol
(i.e. all Redis clients work)

–

works well for synchronous req/rep and streams

–

reimplementation of Redis core in Go

–

think of it as « live environment variables »,
that you can watch/subscribe to

What's Docker exactly?
●

rewrite of dotCloud internal container engine
–
–

●

original version: Python, tied to dotCloud's internal stuff
released version: Go, legacy-free

the Docker daemon runs in the background
–

manages containers, images, and builds

–

HTTP API (over UNIX or TCP socket)

–

embedded CLI talking to the API

●

Open Source (GitHub public repository + issue tracking)

●

user and dev mailing lists

Docker: the community
●

Docker: >200 contributors

●

<7% of them work for dotCloud Docker inc.

●

latest milestone (0.6): 40 contributors

●

~50% of all commits by external contributors

●

GitHub repository: >800 forks

Docker Inc.: the company
●

dotCloud Inc.
–
–

2010: YCombinator

–

2011: 10M$ funding by Trinity+Benchmark

–
●

the first polyglot PAAS ever

2013: start Docker project

Docker Inc.
–

March 2013: public repository on GitHub

–

October 2013: name change

Docker: the ecosystem
●

Cocaine (PAAS; has Docker plugin)

●

CoreOS (full distro based on Docker)

●

Deis (PAAS; available)

●

Dokku (mini-Heroku in 100 lines of bash)

●

Flynn (PAAS; in development)

●

Maestro (orchestration from a simple YAML file)

●

OpenStack integration (in Havana, Nova has a Docker driver)

●

Pipework (high-performance, Software Defined Networks)

●

Shipper (fabric-like orchestration)
And many more; including SAAS offerings (Orchard, Quay...)

Docker long-term roadmap
●

Today: Docker 0.6
–
–

●

LXC
AUFS

Tomorrow: Docker 0.7
–
–

●

LXC
device-mapper thin snapshots (target: RHEL)

The day after: Docker 1.0
–

LXC, libvirt, qemu, KVM, OpenVZ, chroot…

–

multiple storage back-ends

–

plugins

Thank you! Questions?
http://docker.io/
http://docker.com/
https://github.com/dotcloud/docker
@docker
@jpetazzo

device-mapper thin snapshots
(aka « thinp »)
●

start with a 10 GB empty ext4 filesystem
–

●

snapshot: that's the root of everything

base image:
–
–

untar image on the clone

–
●

clone the original snapshot
re-snapshot; that's your image

create container from image:
–

clone the image snapshot

–

run; repeat cycle as many times as needed

AUFS vs THINP
AUFS
●

●

●

●

easy to see changes
small change =
copy whole file
~42 layers
patched kernel
(Debian, Ubuntu OK)

THINP
●

●

●

●

must diff manually
small change =
copy 1 block (100k-1M)
unlimited layers
stock kernel (>3.2)
(RHEL 2.6.32 OK)

●

efficient caching

●

duplicated pages

●

no quotas

●

FS size acts as quota

Misconceptions about THINP
●

●

●

●

« performance degradation »
no; that was with « old » LVM snapshots
« can't handle 1000s of volumes »
that's LVM; Docker uses devmapper directly
« if snapshot volume is out of space,
it breaks and you lose everything »
that's « old » LVM snapshots; thinp halts I/O
« if still use disk space after 'rm -rf' »
no, thanks to 'discard passdown'

Let's Containerize New York with Docker!

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