nomad-nodesim

Nomad Client Node Simulator

To install and use you must have Go 1.19+ and run:

go install -v  github.com/schmichael/nomad-nodesim@latest

nomad-nodesim -help

See nodesim.nomad for an example jobspec for running nodesim in a Nomad cluster using Docker.

See terraform for some of the worst Packer and Terraform code you have ever seen. Should provision a working Nomad cluster (in AWS us-west-2) to run nodesim.nomad.

Gotchas

Disable limits! Otherwise you won't scale far: https://developer.hashicorp.com/nomad/docs/configuration#limits
If Consul is running it may try to perform 1 health check per virtual node against the real nodes which... can get a little intense.

Why?

To simulate clusters orders of magnitude larger than the number of physical machines.

Also a useful exploration of how pluggable the client is.

What Works

Hundreds of clients per process.
Client restarting.

What Could Work

Features that aren't support today but could be:

Replace Config.RPCHandler with a simulated network stack
Server mode
Task Driver Plugins (or a builtin fake one)
Configuration file instead of args
Add universal "?node_id=..." HTTP API support upstream to route the RPCs to individual Client instances.

What Won't Work

Features that probably can't be supported: