Rolling Updates

• Service Update default: replace each replica, one at a time

• We can customize a lot of that update process

• Before going live in production, test this a lot

• Different apps handle session and reconnection differently

• Few apps do this well, even with orchestrator help

There will be quite a lot of hands on and demo examples for which we need:

New Testing Tool: httping

• Test a HTTP(s) connection similar to how ping works

• Shows HTTP response code, colors, CLI GUI and more

• https://hub.docker.com/r/bretfisher/httping/

• We'll use container image from Bret Fisher, but also avail on

  • brew install httping

  • apt-get install httping

  • no easy build for Windows

• docker run bretfisher/httping localhost works everywhere

New Testing App: browncoat

• Simple web app with settings for acting badly

• https://hub.docker.com/r/bretfisher/browncoat/

• By default, no healthcheck, but functions correctly

• Different image tags and envvars for changing behavior

• Purpose: test rolling updates, rollbacks, and healthchecks

Requirements for the sub-section examples

• Created a 3-node (or more) Swarm cluster

• Created the swarm Visualizer service

  • docker run -it -d -p 5000:8080 -v /var/run/docker.sock:/var/run/docker.sock dockersamples/visualizer

• Visualizer looks like this:

External links

• https://docs.docker.com/engine/swarm/swarm-tutorial/rolling-update/