what mean about PG WANTEDGENERATION and PG CURRENTGENERATION

[jackin853]

I just learned the stolon framework, and I encountered some concepts that I don't understand very well, and I didn't find any relevant explanations in the relevant documents.
When I use the stolonctl status command to get the cluster status, I see the following two columns in the status of the keepers. I don't know what it means. The two values are sometimes the same, sometimes different. What does the same value mean? What's the difference?
PG WANTEDGENERATION PG CURRENTGENERATION

[viggy28]

I agree, that it would be nice to improve the documentation around these internal concepts.

Let me explain what I understand.

When the db spec changes, sentinel increases the db.Generation by 1.

stolon/cmd/sentinel/cmd/sentinel.go

Line 1560 in e48f9a4

db.Generation++

If the keeper is healthy, then it would likely update the spec change and finally keeper sets local status with db.generation.

stolon/cmd/keeper/cmd/keeper.go

Line 1741 in 5dc6358

if err := p.saveDBLocalState(ndbls); err != nil {

Keeper reports the updated local state generation and sentinel updates db.status.currentGeneration with db.generation

stolon/cmd/sentinel/cmd/sentinel.go

Line 301 in e48f9a4

db.Status.CurrentGeneration = dbs.Generation

Overall, why we doing all these is a way to identify that whether the databases (keepers) are converged or not. @sgotti feel free to correct me wherever I am wrong :)

[jackin853]

@viggy28 Thanks，I got it