The OTLP receiver can now considered stable. We've had it for longer
than a year in main and has received constant improvements.
Signed-off-by: Jesus Vazquez <jesusvzpg@gmail.com>
The instant vector documentation does not explain which metric samples are selected - in particular, it makes no reference to staleness.
It's confusing when reading the docs to understand how exactly Prometheus selects the metrics to report: the most recent sample older than the search timestamp specified in the API request, so long as that metric is not "stale".
Signed-off-by: Craig Ringer <craig.ringer@enterprisedb.com>
In detail:
- Clarify that label name and value length limits are in byte,
not in UTF-8 data points.
- More consistent formatting to keep 80 characters line limet.
- Clarify various misleading specifications around "per sample",
"per scrape", "per scrape config", "per job"...
- Fix grammar.
Signed-off-by: beorn7 <beorn@grafana.com>
The linear interpolation (assuming that observations are uniformly
distributed within a bucket) is a solid and simple assumption in lack
of any other information. However, the exponential bucketing used by
standard schemas of native histograms has been chosen to cover the
whole range of observations in a way that bucket populations are
spread out over buckets in a reasonably way for typical distributions
encountered in real-world scenarios.
This is the origin of the idea implemented here: If we divide a given
bucket into two (or more) smaller exponential buckets, we "most
naturally" expect that the samples in the original buckets will split
among those smaller buckets in a more or less uniform fashion. With
this assumption, we end up with an "exponential interpolation", which
therefore appears to be a better match for histograms with exponential
bucketing.
This commit leaves the linear interpolation in place for NHCB, but
changes the interpolation for exponential native histograms to
exponential. This affects `histogram_quantile` and
`histogram_fraction` (because the latter is more or less the inverse
of the former).
The zero bucket has to be treated specially because the assumption
above would lead to an "interpolation to zero" (the bucket density
approaches infinity around zero, and with the postulated uniform usage
of buckets, we would end up with an estimate of zero for all quantiles
ending up in the zero bucket). We simply fall back to linear
interpolation within the zero bucket.
At the same time, this commit makes the call to stick with the
assumption that the zero bucket only contains positive observations
for native histograms without negative buckets (and vice versa). (This
is an assumption relevant for interpolation. It is a mostly academic
point, as the zero bucket is supposed to be very small anyway.
However, in cases where it _is_ relevantly broad, the assumption helps
a lot in practice.)
This commit also updates and completes the documentation to match both
details about interpolation.
As a more high level note: The approach here attempts to strike a
balance between a more simplistic approach without any assumption, and
a more involved approach with more sophisticated assumptions. I will
shortly describe both for reference:
The "zero assumption" approach would be to not interpolate at all, but
_always_ return the harmonic mean of the bucket boundaries of the
bucket the quantile ends up in. This has the advantage of minimizing
the maximum possible relative error of the quantile estimation.
(Depending on the exact definition of the relative error of an
estimation, there is also an argument to return the arithmetic mean of
the bucket boundaries.) While limiting the maximum possible relative
error is a good property, this approach would throw away the
information if a quantile is closer to the upper or lower end of the
population within a bucket. This can be valuable trending information
in a dashboard. With any kind of interpolation, the maximum possible
error of a quantile estimation increases to the full width of a bucket
(i.e. it more than doubles for the harmonic mean approach, and
precisely doubles for the arithmetic mean approach). However, in
return the _expectation value_ of the error decreases. The increase of
the theoretical maximum only has practical relevance for pathologic
distributions. For example, if there are thousand observations within
a bucket, they could _all_ be at the upper bound of the bucket. If the
quantile calculation picks the 1st observation in the bucket as the
relevant one, an interpolation will yield a value close to the lower
bucket boundary, while the true quantile value is close to the upper
boundary.
The "fancy interpolation" approach would be one that analyses the
_actual_ distribution of samples in the histogram. A lot of statistics
could be applied based on the information we have available in the
histogram. This would include the population of neighboring (or even
all) buckets in the histogram. In general, the resolution of a native
histogram should be quite high, and therefore, those "fancy"
approaches would increase the computational cost quite a bit with very
little practical benefits (i.e. just tiny corrections of the estimated
quantile value). The results are also much harder to reason with.
Signed-off-by: beorn7 <beorn@grafana.com>
This change causes Prometheus to allow all UTF-8 characters in metric and label names.
This means that names that were previously invalid and would have been previously rejected will be allowed through.
Signed-off-by: Owen Williams <owen.williams@grafana.com>
Fix call to newTestEngine(t) in promql/engine_test.go:3214.
`agent` feature-flag it's own cmdline flag now.
Remove `scrape.name-escaping-scheme` argument.
Signed-off-by: Jan Fajerski <jfajersk@redhat.com>
PromQL engine: Delay deletion of __name__ label to the end of the query evaluation
- This change allows optionally preserving the `__name__` label via the `label_replace` and `label_join` functions, and helps prevent the dreaded "vector cannot contain metrics with the same labelset" error.
- The implementation extends the `Series` and `Sample` structs with a boolean flag indicating whether the `__name__` label should be deleted at the end of the query evaluation.
- The `label_replace` and `label_join` functions can still access the value of the `__name__` label, even if it has been previously marked for deletion. If `__name__` is used as target label, it won't be dropped at the end of the query evaluation.
- Fixes https://github.com/prometheus/prometheus/issues/11397
- See https://github.com/jcreixell/prometheus/pull/2 for previous discussion, including the decision to create this PR and benchmark it before considering other alternatives (like refactoring `labels.Labels`).
- See https://github.com/jcreixell/prometheus/pull/1 for an alternative implementation using a special label instead of boolean flags.
- Note: a feature flag `promql-delayed-name-removal` has been added as it changes the behavior of some "weird" queries (see https://github.com/prometheus/prometheus/issues/11397#issuecomment-1451998792)
Example (this always fails, as `__name__` is being dropped by `count_over_time`):
```
count_over_time({__name__!=""}[1m])
=> Error executing query: vector cannot contain metrics with the same labelset
```
Before:
```
label_replace(count_over_time({__name__!=""}[1m]), "__name__", "count_$1", "__name__", "(.+)")
=> Error executing query: vector cannot contain metrics with the same labelset
```
After:
```
label_replace(count_over_time({__name__!=""}[1m]), "__name__", "count_$1", "__name__", "(.+)")
=>
count_go_gc_cycles_automatic_gc_cycles_total{instance="localhost:9090", job="prometheus"} 1
count_go_gc_cycles_forced_gc_cycles_total{instance="localhost:9090", job="prometheus"} 1
...
```
Signed-off-by: Jorge Creixell <jcreixell@gmail.com>
---------
Signed-off-by: Jorge Creixell <jcreixell@gmail.com>
Signed-off-by: Björn Rabenstein <github@rabenste.in>
We have not mentioned that experimental PromQL functions might get
removed entirely, although that's one of the most important properties
of functions declared experimental.
Signed-off-by: beorn7 <beorn@grafana.com>
avoid simultaneous compactions and reduce stress on shared resources.
This is enabled via `--enable-feature=delayed-compaction`.
Signed-off-by: machine424 <ayoubmrini424@gmail.com>
I often see people ask questions that indicate they don't understand
this point, and launching into "instant vector" and "range vector" is
likely to point them in the wrong direction.
Remove the admonishment that the reader mustn't confuse these things.
Remove mention of "inferred sample timestamps" that is never explained.
Signed-off-by: Bryan Boreham <bjboreham@gmail.com>
Previously, the config doc suggested that scrapes are simply failed if
the bucket limit is exceeded. However, instead Prometheus first
attempts to reduce the resolution. This will succeed in almost all
non-pathological cases. However, in the rare case that it doesn't, the
scrape will be failed after all.
For the resolution limit AKA `native_histogram_min_bucket_factor`, the
logic is a bit different. Once the highest factor, i.e. schema -4, is
reached, the scrape will still succeed.
Signed-off-by: beorn7 <beorn@grafana.com>
Julien