This is a bit tough to explain, but I'll try:
`rate` & friends have a sophisticated extrapolation algorithm.
Usually, we extrapolate the result to the total interval specified in
the range selector. However, if the first sample within the range is
too far away from the beginning of the interval, or if the last sample
within the range is too far away from the end of the interval, we
assume the series has just started half a sampling interval before the
first sample or after the last sample, respectively, and shorten the
extrapolation interval correspondingly. We calculate the sampling
interval by looking at the average time between samples within the
range, and we define "too far away" as "more than 110% of that
sampling interval".
However, if this algorithm leads to an extrapolated starting value
that is negative, we limit the start of the extrapolation interval to
the point where the extrapolated starting value is zero.
At least that was the intention.
What we actually implemented is the following: If extrapolating all
the way to the beginning of the total interval would lead to an
extrapolated negative value, we would only extrapolate to the zero
point as above, even if the algorithm above would have selected a
starting point that is just half a sampling interval before the first
sample and that starting point would not have an extrapolated negative
value. In other word: What was meant as a _limitation_ of the
extrapolation interval yielded a _longer_ extrapolation interval in
this case.
There is an exception to the case just described: If the increase of
the extrapolation interval is more than 110% of the sampling interval,
we suddenly drop back to only extrapolate to half a sampling interval.
This behavior can be nicely seen in the testcounter_zero_cutoff test,
where the rate goes up all the way to 0.7 and then jumps back to 0.6.
This commit changes the behavior to what was (presumably) intended
from the beginning: The extension of the extrapolation interval is
only limited if actually needed to prevent extrapolation to negative
values, but the "limitation" never leads to _more_ extrapolation
anymore.
The difference is subtle, and probably it never bothered anyone.
However, if you calculate a rate of a classic histograms, the old
behavior might create non-monotonic histograms as a result (because of
the jumps you can see nicely in the old version of the
testcounter_zero_cutoff test). With this fix, that doesn't happen
anymore.
Signed-off-by: beorn7 <beorn@grafana.com>
The last_over_time retains a histogram sample without making a copy.
This sample is now coming from the buffered iterator used for windowing functions,
and can be reused for reading subsequent samples as the iterator progresses.
I would propose copying the sample in the last_over_time function, similar to
how it is done for rate, sum_over_time and others.
Signed-off-by: Filip Petkovski <filip.petkovsky@gmail.com>
promql: Extend testing framework to support native histograms
This includes both the internal testing framework as well as the rules unit test feature of promtool.
This also adds a bunch of basic tests. Many of the code level tests can now be converted to tests within the framework, and more tests can be added easily.
---------
Signed-off-by: Harold Dost <h.dost@criteo.com>
Signed-off-by: Gregor Zeitlinger <gregor.zeitlinger@grafana.com>
Signed-off-by: Stephen Lang <stephen.lang@grafana.com>
Co-authored-by: Harold Dost <h.dost@criteo.com>
Co-authored-by: Stephen Lang <stephen.lang@grafana.com>
Co-authored-by: Gregor Zeitlinger <gregor.zeitlinger@grafana.com>
The operator changes the meaning of the metric, so the metric name should
be dropped. Technically this would be a breaking change, but it's also very
obviously a bug and not likely that anyone depends on it.
Signed-off-by: Julius Volz <julius.volz@gmail.com>
This commit adds `@ <timestamp>` modifier as per this design doc: https://docs.google.com/document/d/1uSbD3T2beM-iX4-Hp7V074bzBRiRNlqUdcWP6JTDQSs/edit.
An example query:
```
rate(process_cpu_seconds_total[1m])
and
topk(7, rate(process_cpu_seconds_total[1h] @ 1234))
```
which ranks based on last 1h rate and w.r.t. unix timestamp 1234 but actually plots the 1m rate.
Signed-off-by: Ganesh Vernekar <cs15btech11018@iith.ac.in>
* Separate tests into:
** Aggregators
** Functions
** Operators
** Selectors
* Remove simple files and place tests into other files.
* Eliminate some of the _over_time tests since there are already plenty of
edge cases present in the functions.test file.
Relates to #740
Signed-off-by: Harold Dost <harolddost@gmail.com>
* Use go1.14 new hash/maphash to hash both RHS and LHS instead of XOR'ing
which has been resulting in hash collisions.
Signed-off-by: Callum Styan <callumstyan@gmail.com>
* Refactor engine labelset signature generation, just use labels.Labels
instead of hashes.
Signed-off-by: Callum Styan <callumstyan@gmail.com>
* Address review comments; function comments + store result of
lhs.String+rhs.String as key.
Signed-off-by: Callum Styan <callumstyan@gmail.com>
* Replace all signatureFunc usage with signatureFuncString.
Signed-off-by: Callum Styan <callumstyan@gmail.com>
* Make optimizations to labels String function and generation of rhs+lhs
as string in resultMetric.
Signed-off-by: Callum Styan <callumstyan@gmail.com>
* Use separate string functions that don't use strconv just for engine
maps.
Signed-off-by: Callum Styan <callumstyan@gmail.com>
* Use a byte invalid separator instead of quoting and have a buffer
attached to EvalNodeHelper instead of using a global pool in the labels
package.
Signed-off-by: Callum Styan <callumstyan@gmail.com>
* Address review comments.
Signed-off-by: Callum Styan <callumstyan@gmail.com>
* Address more review comments, labels has a function that now builds a
byte slice without turning it into a string.
Signed-off-by: Callum Styan <callumstyan@gmail.com>
* Use two different non-ascii hex codes as byte separators between labels
and between sets of labels when building bytes of a Labels struct.
Signed-off-by: Callum Styan <callumstyan@gmail.com>
* We only need the 2nd byte invalid sep. at the beginning of a
labels.Bytes
Signed-off-by: Callum Styan <callumstyan@gmail.com>
This makes things generally more resilient, and will
help with OpenMetrics transitions (and inconsistencies).
Signed-off-by: Brian Brazil <brian.brazil@robustperception.io>
