Docker at DevTable
Docker at DevTable
What is DevTable?
DevTable is a browser-based, hosted, collaborative IDE
Develop in the cloud with the same power as your desktop applications
Code
Collaborate
Debug and Test
Deploy
● Google App Engine● REST● SCP● Git (Heroku and other providers)
Sealed evil in a can
There are a lot of neat things that we run for our users, but they are all potentially very dangerous:
● App Engine Development Server● Debuggers and Emulators● REPLs (Python, etc)● Terminal support (which means all of the
above as well)
Why this is a problem
● Without a containment system of some kind, any of these awesome features would allow users to cause mayhem:
○ A REPL use could open any file○ A DevServer can execute arbitrary code○ A terminal could allow anything to happen
Why not simply use permissions?
● Permissions solve the file access problem● Permissions do not prevent users from
causing other system issues: instability, exhaustion, escalation, etc
Solution: containers!
To contain the insecurity of running live code, we run all non-custom code in a container, with only the user’s project mounted and available
Evil (not to scale)
Project data
Container
Ideal container properties
● Lightweight● Secure● Easy to manage● FAST
Originally we used LXC...
● Lightweight (sort of…)● Secure● Easy to manage (sort of...)● FAST
In the beginning, there was LXC...
… and it was slow.
● Typical startup times for our containers were on the order of minutes
● Starting a debugger or shell is not fun at those speeds
● Getting the security and management just right was quite painful
Then the community said “let there be Docker”...
Yo!
… and it made things amazing.
Our average startup time for a container has dropped from over a minute to just under
four seconds.
LXC
Docker
Go make a cup of coffee and play swords on office chairs
Go!
Before Docker
But, but Docker is just... LXC...
Almost, Docker does some things that make starting up single processes lightning quick:
● Incremental by default● Replace distro init process with lightweight
version● No DHCP, upstart, dnsmasq, etc.● Aufs seems to be faster than OverlayFS● Build process is MUCH better (Dockerfiles)
Docker at DevTable
The fun technical details!
DevTable overview
Clients
Web browsers
Clients - Web
browsers
Frontends
Python
Clients - Web
browsers
Backends
C#
WebSocket Socket
DFS
Clients - Web
browsers
Container Servers
Python
Thrift
SSH
HTTP
?
Images
Things we’ll discuss today
Clients
Web browsers
Clients - Web
browsers
Frontends
Python
Clients - Web
browsers
Backends
C#
WebSocket Socket
DFS
Clients - Web
browsers
Container Servers
Python
ThriftHTTP
SSH
?
Images
How we use docker now
● Python Docker API bindings● Run a single instance per project● Mount only the files relevant to the project in
the container● Run an SSH “command and control” process● Execute user processes through SSH● Dynamic version of Docker port forwarding
Backend <-> Container server
Backends
C#
Container Servers
Python
Thrift
Container server
The container server is the server in charge of managing all aspects related to the Docker containers
● Written in Python● Conforms to a Thrift interface● Called by the Backends to start containers,
stop containers, run commands, mount file systems in containers, etc
Container server
startContainer Starts a new container for a project.
runCommand
Runs a command inside a container
stopCommand
Stops a command inside a container
notifyFilesModifed
Notifies a container that a file has been modified by the backend
stopContainer
Stops a container
Handling file changes
● Changes made by the container or the backend to the DFS are propagated automatically
● However, both sides have code that depends on notification of changes
● Each server notifies the other about changes that occur via a notification service
DFS change notifications
Backend
C#
Container Server
Python
Hey, a user added file “test.txt” in container 1234
Backend
C#
Container Server
Python
Hey, the user changed file “foo.py” in container 1
How we handle file changes in Docker
● The container server watches changes inside the container using inotify, and reports changes to the backend
● The backend reports changes to the container server which will touch files that have been added or changed
Container server <-> Docker
Clients - Web
browsers
Container Servers
Python
SSH
Container server <-> Docker
We use the Python Docker bindings to create a new image and load it with a temporary ssh key
New container requests bring up the container with the known session SSH key and issue commands to the container via SSH
Much better than LXC issuing commands via subprocess
Docker <-> Outside world
For many services we run (such as the App Engine Development Server), we need to expose the server running inside Docker to the outside world
Docker <-> Outside world
HTTPClients
Web browsers
HTTP
Container Server
HAProxy
Docker <-> Outside world
Services inside of Docker as exposed via dynamic port mapping to a HAProxy running on the container server
The HAProxy exposes the port by remapping it to the external port and a custom subdomain
Docker <-> Outside world
Container Server
93nx83ndsc34mn.c4.devtable.io:80Clients
Web browsers
Port 38563
HAProxy
Example: running a dev server
1. Backend requests a container from the server
Backend
C#
Container Server
Python
I need a container for project “testapplication”
Container “container1234” started for project
Example: running a dev server
2. Backend registers for file notification events
Backend
C#
Container Server
Python
Let me know if any files change
Duly noted
Example: running a dev server
3. Backend asks for the dev server to be started and port 80 to be forwarded
Backend
C#
Container Server
Python
Please start the dev server and forward port 80
Dev server started and port is forwarded at subdomain foobarbaz
Example: running a dev server
1. Container server tells Docker to start a container
Container Server
Python
create_container, mount_filesystem, forward_port, start_ssh
Done. Port exposed: 84639
Example: running a dev server
2. Container server tells HAProxy to forward the port returned by docker
Container Server
Python
Forward port 84639 as subdomain foobarbaz
HAProxy
Example: running a dev server
3. Container server tells Docker to run the dev server
Container Server
Python
ssh command_for_devserver
Summary
Docker has allowed DevTable to run amazing tools securely and fast, without a large management overhead
Future opportunities
Docker presents some amazing new opportunities for DevTable and the community:
● Ability to quickly load (and save) complete development environments, securely
● Ability to quickly write custom plugins and run them in our IDE (want to analyze and build Go? just give us a URL or a Dockerfile!)
But wait…
There’s something that has been bugging us…
How should we distribute our private images in production?
Quay Demo
At this point in the live talk we unveiled and gave a demo of our hosted private docker registry called Quay.io.
Questions? Comments? Witty anecdotes?
devtable.com
Jacob Moshenko - [email protected] Schorr - [email protected]