fly-replay machine wake-up in case there are multiple machines in a region


The documentation mentions -

For an application with multiple machines with the same configuration, requests will be distributed across them. Warm-start behavior in this situation is not well-defined now, so should not be relied upon for apps with multiple machines.
(via Working with the Machines API · Fly Docs)

The wake-on-request behavior described above will be unpredictable when running more than one machine per region.
(via Run User Code on Fly Machines · Fly Docs)

I want to know the behavior in case a fly-replay header is being used to send the request to a specific machine - fly-replay: app=game-server;instance=<id>

if there are two game servers running in the same region, is that still expected to cause warm start problems?

Hi @hi.kanily !

The fly-replay header already knows the instance to route the request to specified in your given instance id.

Therefore only that machine instance should get woken up. Other similar machine instances in the region hopefully should not. But do try it out and see if behavior works as expected!