I have some questions regarding scaling up Azure Functions and the Event Hub trigger. I understand that an AF app stores a checkpoint number somewhere (Azure Storage I think), but I am wondering to what this applies (the affinity) when AF scales up or changes.
- If I have an existing event hub with messages and redeploy the AF app, will it restart from the beginning with a new checkpoint, or will it start where it left off? Seems like it should start from the last checkpoint for that AF app somehow.
- If I change the name of a function in the AF app which uses an event hub trigger, does it keep the same checkpoint or start over?
- If I stop/start the AF app, does it lose its position? Seems like it shouldn't since it's stored externally, but I don't know how they map to each other.
- When AF scales up, do the multiple instances all share the same checkpoint, or do subsequent instances start at the beginning and have their own? The latter seems unlikely. From what I've read, a new EventProcessorHost is created for each AF app instance, but do they all share the same checkpoint?
- When scaling up, do the new AF app instances start at the existing/initial instance's checkpoint, or does the new EPH start from the beginning?
In case it matters, I am using C# DLLs and VS2015 for dev, and VSTS for building/deploying.