[Bug] Fixes issue where the combiner can return no data when max series is hit - #6099
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… was hit Signed-off-by: Joe Elliott <number101010@gmail.com>
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…es is hit (grafana#6099) * fix bug where combiner could return an empty response when max series was hit Signed-off-by: Joe Elliott <number101010@gmail.com> * changelog Signed-off-by: Joe Elliott <number101010@gmail.com> --------- Signed-off-by: Joe Elliott <number101010@gmail.com>
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What this PR does:
This issue was discovered while working on integration tests and would be difficult but not impossible to trip in a real environment. If the combiner hit max series but had not yet received it's metadata response then it would still return true from shouldQuit(). This caused it to return an empty response when GRPCDiff() was called b/c it didn't think it had any complete data.
Also added a note about using GRPCFinal(). That was changed here, but perhaps we should revisit. Grafana has added the ability to accept larger websocket payloads and sending a complete final message would avoid bugs like this.
Checklist
CHANGELOG.mdupdated - the order of entries should be[CHANGE],[FEATURE],[ENHANCEMENT],[BUGFIX]