Nomad Job Update Strategies

Most applications are long-lived and need to be updated over time. Nomad has built-in support for rolling, blue/green, and canary updates through the job "update" stanza, and they work equally well with non-containerized and containerized workloads.

In this lab you deploy a real chat application on a 4-node Nomad cluster (1 server, 3 clients) backed by Consul service discovery and Consul Connect. NGINX acts as a load balancer that forwards requests to instances of the chat app, which stores its messages in a single MongoDB database reached over the Connect service mesh. The chat app's background color changes between versions so you can watch each rollout happen in real time:

• Start with a light-background build run by Nomad's exec task driver from a compiled node.js binary.
• Use a rolling update to switch to a dark-background binary, one instance at a time.
• Use a blue/green deployment to move to a Docker version with the light background, then promote it.
• Use a canary deployment to try a Docker version with the dark background, then roll it back.

You will also learn how Nomad lets you promote or fail blue/green and canary deployments so you can either ship a change or revert it. Follow the accompanying Nomad Job Update Strategies tutorials for more background.

We recommend completing the Nomad Basics, Nomad Simple Cluster, and Nomad Multi-Server Cluster labs first.