transitivity of remote read/write api

[Johny]

experimentally, I'm able to read data from downstream Prometheus instances with 3-4 levels between them. For example, consider this for simplicity

PromA   -----remote-read----> PromB ----remote-read-----> ExternalStorage

I am able to get data points in PromA that are fetched remotely from ExternalStorage. Similarly, I am able to write data points from PromA to ExternalStraoge.

Is there any caveat with this approach besides reliability issues in introducing multiple points of failure on the read/write path?

[Julius Volz]

The reliability issues are the only ones I can think of, but especially in the following sense:

* If only you have A->B and B cannot be reached while running a query from A, the query result will contain a warning about that which will also be shown in the graph UI.

* If you have A->B->C and C cannot be reached while running a query from A, that warning doesn't make it all the way back, so you just get an empty result set without the warning.

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Julius Volz

PromLabs - promlabs.com