prometheus/storage
beorn7 4696b46dd5 storage: Fix mixed samples handling in sampleRing
Two issues are fixed here, that lead to the same problem:

1. If `newSampleRing` is called with an unknown ValueType including
   ValueNone, we have initialized the interface buffer (`iBuf`).
   However, we would still use a specialized buffer for the first
   sample, opportunistically assuming that we might still not
   encounter mixed samples and we should go down the more efficient
   road.

2. If the `sampleRing` is `reset`, we leave all buffers alone,
   including `iBuf`, which is generally fine, but not for `iBuf`, see
   below.

In both cases, `iBuf` already contains values, but we will fill one of
the specialized buffers first. Once we then actually encounter mixed
samples, the content of the specialized buffer is copied into `iBuf`
using `append`. That's by itself the right idea because `iBuf` might
be `nil`, and even if not, it might or might not have the right
capacity. However, this approach assumes that `iBuf` is empty, or more
precisely has a length of zero.

This commit makes sure that `iBuf` does not get needlessly initialized
in `newSampleRing` and that it is emptied upon `reset`.

A test case is added to demonstrate both issues above.

Signed-off-by: beorn7 <beorn@grafana.com>
2023-10-31 16:18:09 +01:00
..
remote
buffer.go storage: Fix mixed samples handling in sampleRing 2023-10-31 16:18:09 +01:00
buffer_test.go storage: Fix mixed samples handling in sampleRing 2023-10-31 16:18:09 +01:00
fanout.go
fanout_test.go
generic.go
interface.go
lazy.go
memoized_iterator.go
memoized_iterator_test.go
merge.go
merge_test.go
noop.go
secondary.go
series.go
series_test.go