This is, sadly, the only way to avoid a breaking change. The cost is
that anyone using exemplars has to perform a type assertion. This is,
however, a common pattern where interfaces turn out to need additional
methods in a stable library or only some implementations can provide
the additional methods (AKA "interface upgrade").
Needless to say that in v2 of this library, we'll do things in a more
straight forward way.
Signed-off-by: beorn7 <beorn@grafana.com>
Contrary to the code comment, I see no `basicMetricVec` implementation.
Grep'ing this project shows this is the only reference. So I suspect
it's an outdated comment and can be removed to minimize confusion.
I'm unclear whether other parts of that comment are also incorrect and
need updating.
Signed-off-by: Jeff Widman <jeff@jeffwidman.com>
The `const separatorByte` wasn't used anymore actually. In `vec.go`,
we were using `model.SeparatorByte`, which is better anyway. So remove
the unused constant and initialize `separatorByteSlice` with
`model.SeparatorByte`, too.
Signed-off-by: beorn7 <beorn@grafana.com>
This is a much stronger hash function than fnv64a and comparably fast
(with super-fast assembly implementation for amd64).
Performance is not critical here anyway.
The old fnv64a is kept for vectors, where collision detection is in
place and the weakness of the hashing doesn't matter that much. I
implemented a vector version with xxhash and found that xxhash is
slower in all cases except very very high cardinality (where it is
only slightly faster). Also, ``xxhash.New`` comes with an allocation
of 80 bytes. Thus, to keep vectors alloc-free, we needed to add a
`sync.Pool`, which would have an additional performance overhead.
Signed-off-by: beorn7 <beorn@grafana.com>
This makes the collisions a bit less likely by XOR'ing descIDs rather
than adding them up for the collectorID.
Signed-off-by: beorn7 <beorn@grafana.com>
Flush is another of the methods that will call WriteHeader if it
hasn't happened yet. Since we want to call observeWriteHeader (if
set), we need to do the WriteHeader call already here, similar to what
we have done in Write and ReadFrom.
This commit also adds comments explaining the above to not tempt
developers to remove the WriteHeader call.
Signed-off-by: beorn7 <beorn@grafana.com>
It is perfectly possible that a normal GC happens just before the
forced one. Thus seeing 2 GCs is fine.
Whenever this test failed, it was because two GCs were seen.
Signed-off-by: beorn7 <bjoern@rabenste.in>
This is really lame as it essentially just uses longer times to
wait. The test is still timing-dependent and thus could still
theoretically fail with unlucky scheduling. However, we are testing
something that _is_ about timing. Turning this all into something not
timing-dependent would be first quite involved and second might defeat
the purpose of testing code that is inherently about timing.
Let's see how this works out in practice.
Signed-off-by: beorn7 <bjoern@rabenste.in>
We stopped advertising binary-wide setting of a label quite a while
ago. This doc comment was missed in the cleanup.
Signed-off-by: beorn7 <bjoern@rabenste.in>
beorn7