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.

Build & Deploy

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!

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