Querier: propagate errors with status code 422 coming from the store-gateway

[duricanikolic]

What this PR does

This PR introduces the following changes:

• Makes the querier propagate errors with status code 422 coming from the store-gateway
• New integration tests have been added in store_gateway_limits_hit_test.go: they ensure that when the max-fetched-chunks-per-query or max-fetched-series-per-query limits are hit, both store-gateway and querier will return a 422 status code

Which issue(s) this PR fixes or relates to

Extension of the fix for issue #3382

Checklist

• Tests updated
• Documentation added
• CHANGELOG.md updated - the order of entries should be [CHANGE], [FEATURE], [ENHANCEMENT], [BUGFIX]

[pracucci]

store_gateway_client.go and store_gateway_test.go have been moved from the querier to the storegatewaypb package

The *pb packages should contain only protobufs.

That being said I don't think an integration should use a gRPC client. The idea of integration tests is that they should emulate how users use the system. Let's talk on Slack about it, so we can see if we can find a better approach for the testing here.

[duricanikolic]

The *pb packages should contain only protobufs.
@pracucci I have fixed that and moved the 2 sources to the storegateway package instead.

For the rest, let's discuss it next week after you have reviewed the code.

[56quarters]

WDYT about putting this in storegateway/client, same as we do for the ingester client?

[duricanikolic]

@56quarters I had a call with @colega in which we discussed that probably the whole implementation of store_gateway_client.go (currently belonging to the querier, and not storegateway package), as well as of pool.go were done before we started using generics, and therefore the implementation looked a bit more complicated than it should be. The changes I made in store_gateway_client.go were needed for a new test that I introduced, and that will now be removed. So, I will also remove the changes I did there. Nevertheless, we find that it might be appropriate to introduce generics in pool.go and related sources, and to update mimir accordingly. What do you think about that?

[pracucci]

Good job! The fix LGTM. I left few comments about the integration test cause I think we can further simplify it.

[pracucci]

Thanks for your patience. Left few more comments.