Deploy Nodejs with Docker & CoreOS

Edwin Fuquen

edwin@somespider.com

@efuquen

• A tool to conveniently manage containers.
• Containers share the same kernel of the host, but have different filesystems.
• Like lightweight VMs.
• The power of docker is the creation of lightweight, consistent, and easily shareable environments for running applications.

Dockerfile

• Is a build scripts
• Each line is a layer
• Layers build on top of each other successively
• Similar to git commits

quay.io/org/app-base

quay.io/org/app

CoreOS

• Linux OS based on Chrome OS, which itself is based on Gentoo.
• There is no package manager, and only a few preinstalled tools.
• The most essential being docker, etcd, & fleetd.
• An OS fully built around managing containers in a distributed, fault tolerant cluster of machines.

• A distributed key/value store.
• Meant for config data, not high latency/throughput.
• Strongly consistent, very reliable.
• Think zookeeper replacement.

Fleetd

• Uses etcd to make a distributed init system.
• Essential runs systemd services on nodes.
• Feed in standard systemd unit files.
• But with some optional Fleet metadata.

Service Unit File

[Unit]
Description=registrator
Documentation=https://github.com/progrium/registrator
X-Image=progrium/registrator:master

[Service]
EnvironmentFile=/etc/environment
ExecStartPre=/usr/bin/docker pull progrium/registrator:master
ExecStart=/bin/sh -c "docker run \
  --name %p.%i \
  -v /var/run/docker.sock:/tmp/docker.sock \
  progrium/registrator:master -ip $COREOS_PRIVATE_IPV4 \
  etcd://$COREOS_PRIVATE_IPV4:4001/services"
ExecStop=/usr/bin/docker rm -f %p.%i
TimeoutStartSec=180s
TimeoutStopSec=30s
RestartSec=30s
Restart=on-failure

[X-Fleet]
X-Conflicts=%p@*.service
MachineMetadata=role=web

Service Discovery

• App ip & port are registered in etcd.
• confd gets notified when certain keys in etcd are modified
• Then haproxy.cfg templates get updated with added or removed app ip & port.

https://github.com/efuquen/docoreos-express-demo

Docker Issues

• Daemon can leak memory.
• Docker builds can take a long time, lots of data.
• Docker pulls not verified.
• Containers don't persist.

Mitigation

• Don't log lots of data to stdout & stderr.
• Use smaller base images (i.e. debian & busybox).
• Follow image building best practices.
• Use an internal registry.
• Use data only containers for db's (still annoying).

CoreOS Issues

• Hard to install custom tools on the host.
• BTRFS has many maintenance issues.
• Docker has issues playing nice with systemd (mostly an issue with the docker daemon).

Mitigation

• Use privileged throwaway containers for ops work.
• Automate BTRFS cleanup/maintenance (and ext4 is in Alpha).
• systemd-docker: good writeup on the issue here.
• Rocket ... ?

TheMid

• New media site, establishing publishing platform.
• We're Hiring!
• Software Developer & Data Science roles
• jobs@themid.com
• themid.com/careers

ScriptEd >_

• Nonprofit puts developers in NYC high schools and provides paid summer internships.
• March 4 - NYC Tech Community Engagement Event.
• Contact sue@scripted.org

Script Event RSVP: http://scriptedinternships.splashthat.com

Thanks!