prometheus

Commit Graph

Author	SHA1	Message	Date
Owen Williams	8d4bcd2c77	promql: Fix various UTF-8 bugs related to quoting Fixes UTF-8 aggregator label list items getting mutated with quote marks when String-ified. Fixes quoted metric names not supported in metric declarations. Fixes UTF-8 label names not being quoted when String-ified. Fixes https://github.com/prometheus/prometheus/issues/15470 Fixes https://github.com/prometheus/prometheus/issues/15528 Signed-off-by: Owen Williams <owen.williams@grafana.com> Co-authored-by: Bryan Boreham <bjboreham@gmail.com>	1 year ago
Neeraj Gartia	7fd3b13bd2	[TEST] PromQL: Adds tests with histograms for simple functions (#15488 ) adds tests with histograms for simple functions Signed-off-by: Neeraj Gartia <neerajgartia211002@gmail.com> --------- Signed-off-by: Neeraj Gartia <neerajgartia211002@gmail.com>	1 year ago
Neeraj Gartia	4aeed2c4b1	fix resets function for histograms Signed-off-by: Neeraj Gartia <neerajgartia211002@gmail.com>	1 year ago
Neeraj Gartia	0de340c1b4	ignore histogram in dateWrapper Signed-off-by: Neeraj Gartia <neerajgartia211002@gmail.com>	1 year ago
Neeraj Gartia	36e0897f0f	[BUGFIX] PromQL: Fix behaviour of `changes()` for mix of histograms and floats (#15469 ) PromQL: Fix behaviour of changes() for mix of histograms and floats --------- Signed-off-by: Neeraj Gartia <neerajgartia211002@gmail.com>	1 year ago
Joshua Hesketh	8e3301eb44	Export quantile functions (#15190 ) Export quantile functions For use in Mimir's query engine, it would be helpful if these functions were exported. Co-authored-by: Björn Rabenstein <github@rabenste.in> Signed-off-by: Joshua Hesketh <josh@hesketh.net.au> --------- Signed-off-by: Joshua Hesketh <josh@nitrotech.org> Signed-off-by: Joshua Hesketh <josh@hesketh.net.au> Co-authored-by: Björn Rabenstein <github@rabenste.in>	1 year ago
beorn7	a44c449155	promql: Add NaN tests for avg and avg_over_time Signed-off-by: beorn7 <beorn@grafana.com>	1 year ago
Neeraj Gartia	38bb6ece25	[BUGFIX] PromQL: Fix behaviour of some aggregations with histograms (#15432 ) promql: fix some aggregations for histograms This PR fixes the behaviour of `topk`,`bottomk`, `limitk` and `limit_ratio` with histograms. The fixed behaviour are as follows: - For `topk` and `bottomk` histograms are ignored and add info annotations added. - For `limitk` and `limit_ratio` histograms are included in the results(if applicable). Signed-off-by: Neeraj Gartia <neerajgartia211002@gmail.com>	1 year ago
newtonne	88675710f9	Add support for utf8 names on `/v1/label/:name/values` endpoint Previously, the api was evaluating this regex to determine if the label name was valid or not: `14bac55a99/model/labels.go (L94)` However, I believe that the `IsValid()` function is what ought to be used in the brave new utf8 era. Before ``` $ curl localhost:9090/api/v1/label/host.name/values {"status":"error","errorType":"bad_data","error":"invalid label name: \"host.name\""} ``` After ``` $ curl localhost:9090/api/v1/label/host.name/values {"status":"success","data":["localhost"]} ``` It's very likely that I'm missing something here or you were already planning to do this at some point but I just encountered this issue and figured I'd give it a go. Signed-off-by: Owen Williams <owen.williams@grafana.com>	1 year ago
György Krajcsovits	a48d05912d	nhcb: optimize, do not recalculate suffixes multiple times Reduce string manipulation by just cutting off the histogram suffixes from the series name label once. Signed-off-by: György Krajcsovits <gyorgy.krajcsovits@grafana.com>	1 year ago
Neeraj Gartia	abfc3145a2	apply DRY on clamp (#15441 ) Signed-off-by: Neeraj Gartia <neerajgartia211002@gmail.com>	1 year ago
TJ Hoplock	3e24e84172	fix!: stop unbounded memory usage from query log Resolves: #15433 When I converted prometheus to use slog in #14906, I update both the `QueryLogger` interface, as well as how the log calls to the `QueryLogger` were built up in `promql.Engine.exec()`. The backing logger for the `QueryLogger` in the engine is a `util/logging.JSONFileLogger`, and it's implementation of the `With()` method updates the logger the logger in place with the new keyvals added onto the underlying slog.Logger, which means they get inherited onto everything after. All subsequent calls to `With()`, even in later queries, would continue to then append on more and more keyvals for the various params and fields built up in the logger. In turn, this causes unbounded growth of the logger, leading to increased memory usage, and in at least one report was the likely cause of an OOM kill. More information can be found in the issue and the linked slack thread. This commit does a few things: - It was referenced in feedback in #14906 that it would've been better to not change the `QueryLogger` interface if possible, this PR proposes changes that bring it closer to alignment with the pre-3.0 `QueryLogger` interface contract - reverts `promql.Engine.exec()`'s usage of the query logger to the pattern of building up an array of args to pass at once to the end log call. Avoiding the repetitious calls to `.With()` are what resolve the issue with the logger growth/memory usage. - updates the scrape failure logger to use the update `QueryLogger` methods in the contract. - updates tests accordingly - cleans up unused methods Builds and passes tests successfully. Tested locally and confirmed I could no longer reproduce the issue/it resolved the issue. Signed-off-by: TJ Hoplock <t.hoplock@gmail.com>	1 year ago
beorn7	4b573e0521	promql: Fix subqueries to be really left-open Previously, we managed to get rid of the sample on the left bound later, so the problem didn't show up in the framework tests. But the subqueries were still evaluation with the sample on the left bound, taking space and showing up if returning the subquery result directly (without further processing through PromQL like in all the framework tests). Signed-off-by: beorn7 <beorn@grafana.com>	1 year ago
Björn Rabenstein	125a90899c	promqltest: Complete the tests for info annotations (#15429 ) promqltest: Complete the tests for info annotations So far, we did not test for the _absence_ of an info annotation (because many tests triggered info annotations, which we haven't taken into account so far). The test for info annotations was also missed for range queries. This completes the tests for info annotations (and refactors the many `if` statements into a somewhat more compact `switch` statement). It fixes most tests to not emit an info annotation anymore. Or it changes the `eval` to `eval_info` where we actually want to test for the info annotation. It also fixes a few spelling errors in comments. --------- Signed-off-by: beorn7 <beorn@grafana.com> Signed-off-by: Björn Rabenstein <github@rabenste.in> Co-authored-by: Arve Knudsen <arve.knudsen@gmail.com>	1 year ago
Arve Knudsen	89bbb885e5	Upgrade to golangci-lint v1.62.0 (#15424 ) Signed-off-by: Arve Knudsen <arve.knudsen@gmail.com>	1 year ago
Neeraj Gartia	a6fb16fcb4	PromQL: Convert more native histogram tests to promql-test framework (#15419 ) This converts `TestNativeHistogram_SubOperator` to the promql testing framework. It also removes `TestNativeHistogram_Sum_Count_Add_AvgOperator`, which got converted earlier. Signed-off-by: Neeraj Gartia <neerajgartia211002@gmail.com>	1 year ago
George Krajcsovits	5cd9855999	tests(promql/testdata): add regression test for and-on (#15425 ) * tests(promql/testdata): add regression test for and-on I'd like to use queries of the form "x and on() (vector(y)==1)" to be able to include and exclude series for dashboards. This helps migration to native histograms in dashboards by using a dashboard variable to set "y" to either -1 or 1 to exclude or include the result. Signed-off-by: György Krajcsovits <gyorgy.krajcsovits@grafana.com> --------- Signed-off-by: György Krajcsovits <gyorgy.krajcsovits@grafana.com>	1 year ago
Neeraj Gartia	048222867a	fix count_values for histograms Signed-off-by: Neeraj Gartia <neerajgartia211002@gmail.com>	1 year ago
Charles Korn	62e6e55c07	promql: fix issues with comparison binary operations with `bool` modifier and native histograms (#15413 ) * Fix issue where comparison operations with `bool` modifier and native histograms return histograms rather than 0 or 1 * Don't emit anything for comparisons between floats and histograms when `bool` modifier is used * Don't emit anything for comparisons between floats and histograms when `bool` modifier is used between a vector and a scalar --------- Signed-off-by: Charles Korn <charles.korn@grafana.com>	1 year ago
Charles Korn	45db23617a	promql: fix incorrect "native histogram ignored in aggregation" annotations (#15414 ) Signed-off-by: Charles Korn <charles.korn@grafana.com>	1 year ago
huochexizhan	4f48e76086	chore: fix some function names in comment Signed-off-by: huochexizhan <huochexizhan@outlook.com>	1 year ago
zenador	e13c28bd4a	Use a function to determine if an aggregation function is experimental (#15331 ) Signed-off-by: Jeanette Tan <jeanette.tan@grafana.com>	1 year ago
Neeraj Gartia	789c9b1a5e	[BUGFIX] PromQL: Corrects the behaviour of some operator and aggregators with Native Histograms (#15245 ) PromQL: Correct the behaviour of some operator and aggregators with Native Histograms --------- Signed-off-by: Neeraj Gartia <neerajgartia211002@gmail.com>	1 year ago
Matthieu MOREL	af1a19fc78	enable errorf rule from perfsprint linter Signed-off-by: Matthieu MOREL <matthieu.morel35@gmail.com>	1 year ago
Ben Ye	b7aca45de7	fix round function ignoring enableDelayedNameRemoval feature flag Signed-off-by: Ben Ye <benye@amazon.com>	1 year ago
György Krajcsovits	eafe72a0d0	perf(nhcb): optimize away most allocations in convertnhcb In general aim for the happy case when the exposer lists the buckets in ascending order. Use Compact(2) to compact the result of nhcb convert. This is more in line with how client_golang optimizes spans vs buckets. `aef8aedb4b/prometheus/histogram.go (L1485)` Signed-off-by: György Krajcsovits <gyorgy.krajcsovits@grafana.com>	1 year ago
Alex Greenbank	421a3c22ea	scrape: provide a fallback format (#15136 ) scrape: Remove implicit fallback to the Prometheus text format Remove implicit fallback to the Prometheus text format in case of invalid/missing Content-Type and fail the scrape instead. Add ability to specify a `fallback_scrape_protocol` in the scrape config. --------- Signed-off-by: alexgreenbank <alex.greenbank@grafana.com> Signed-off-by: Alex Greenbank <alex.greenbank@grafana.com> Co-authored-by: Björn Rabenstein <beorn@grafana.com>	1 year ago
Joshua Hesketh	14ef1ce8ab	Round function should ignore native histograms As per the documentation, native histograms are skipped. This is in line with other simpleFunc's. Signed-off-by: Joshua Hesketh <josh@nitrotech.org>	1 year ago
Joshua Hesketh	5a4e4f6936	Fix stddev/stdvar when aggregating histograms, NaNs, and infinities (#14941 ) promql: Fix stddev/stdvar when aggregating histograms, NaNs, and Infs Native histograms are ignored when calculating stddev or stdvar. However, for the first series of each group, a `groupedAggregation` is always created. If the first series that was encountered is a histogram then it acts as the equivalent of a 0 point. This change creates the first `groupedAggregation` with the `seen` field set to `false` if the point is a histogram, thus ignoring it like the rest of the aggregation function does. A new `groupedAggregation` will then be created once an actual float value is encountered. This commit also sets the `floatValue` field of the `groupedAggregation` to `NaN`, if the first float value of a group is `NaN` or `±Inf`, so that the outcome is consistently `NaN` once those values are in the mix. (The added tests fail without this change). Signed-off-by: Joshua Hesketh <josh@nitrotech.org> Signed-off-by: beorn7 <beorn@grafana.com> --------- Signed-off-by: Joshua Hesketh <josh@nitrotech.org> Signed-off-by: beorn7 <beorn@grafana.com> Co-authored-by: beorn7 <beorn@grafana.com>	1 year ago
Arve Knudsen	de16f5e387	[FEATURE] PromQL: Add experimental info function MVP (#14495 ) The `info` function is an experiment to improve UX around including labels from info metrics. `info` has to be enabled via the feature flag `--enable-feature=promql-experimental-functions`. This MVP of info simplifies the implementation by assuming: * Only support for the target_info metric * That target_info's identifying labels are job and instance Also: * Encode info samples' original timestamp as sample value * Deduce info series select hints from top-most VectorSelector --------- Signed-off-by: Arve Knudsen <arve.knudsen@gmail.com> Co-authored-by: Ying WANG <ying.wang@grafana.com> Co-authored-by: Augustin Husson <augustin.husson@amadeus.com> Co-authored-by: Bartlomiej Plotka <bwplotka@gmail.com> Co-authored-by: Björn Rabenstein <github@rabenste.in> Co-authored-by: Bryan Boreham <bjboreham@gmail.com>	1 year ago
Arve Knudsen	e05e97cdd7	evaluator.rangeEval: Split out gatherVector method Signed-off-by: Arve Knudsen <arve.knudsen@gmail.com>	1 year ago
Joshua Hesketh	31d19381f6	Clamp functions should ignore native histograms As per the documentation, native histograms are skipped. This is in line with other `simpleFunc`'s. Signed-off-by: Joshua Hesketh <josh@nitrotech.org>	1 year ago
Arve Knudsen	f7b396a1dc	promql.Engine: Refactor vector selector evaluation into a method (#14900 ) New method is named `evalVectorSelector`. --------- Signed-off-by: Arve Knudsen <arve.knudsen@gmail.com>	1 year ago
Neeraj Gartia	d4b1f9eb33	Corrects the behaviour of binary opperators between histogram and float (#14726 ) promql: corrects binary operators functioning for mixed sample with histogram and float For invalid pairings of sample types, an annotation is added now. Signed-off-by: Neeraj Gartia <neerajgartia211002@gmail.com> --------- Signed-off-by: Neeraj Gartia <neerajgartia211002@gmail.com>	1 year ago
George Krajcsovits	522149a2ae	model: move classic NHCB conversion into its own file (#15156 ) * model: move classic to NHCB conversion into its own file In preparation for #14978. Author: Jeanette Tan <jeanette.tan@grafana.com> 2024-07-03 11:56:48 Signed-off-by: Jeanette Tan <jeanette.tan@grafana.com> Signed-off-by: György Krajcsovits <gyorgy.krajcsovits@grafana.com> Co-authored-by: Jeanette Tan <jeanette.tan@grafana.com> Co-authored-by: György Krajcsovits <gyorgy.krajcsovits@grafana.com> * Better naming from review comment Signed-off-by: György Krajcsovits <gyorgy.krajcsovits@grafana.com> * Add doc strings. Signed-off-by: György Krajcsovits <gyorgy.krajcsovits@grafana.com> --------- Signed-off-by: Jeanette Tan <jeanette.tan@grafana.com> Signed-off-by: György Krajcsovits <gyorgy.krajcsovits@grafana.com> Co-authored-by: Jeanette Tan <jeanette.tan@grafana.com>	1 year ago
Fiona Liao	8650d25804	Add additional basic nhcb unit tests (#15086 ) * Add additional basic nhcb unit tests * Update promql/promqltest/testdata/histograms.test Signed-off-by: Fiona Liao <fiona.liao@grafana.com> Signed-off-by: Fiona Liao <fiona.y.liao@gmail.com> Co-authored-by: George Krajcsovits <krajorama@users.noreply.github.com>	1 year ago
TJ Hoplock	6ebfbd2d54	chore!: adopt log/slog, remove go-kit/log For: #14355 This commit updates Prometheus to adopt stdlib's log/slog package in favor of go-kit/log. As part of converting to use slog, several other related changes are required to get prometheus working, including: - removed unused logging util func `RateLimit()` - forward ported the util/logging/Deduper logging by implementing a small custom slog.Handler that does the deduping before chaining log calls to the underlying real slog.Logger - move some of the json file logging functionality to use prom/common package functionality - refactored some of the new json file logging for scraping - changes to promql.QueryLogger interface to swap out logging methods for relevant slog sugar wrappers - updated lots of tests that used/replicated custom logging functionality, attempting to keep the logical goal of the tests consistent after the transition - added a healthy amount of `if logger == nil { $makeLogger }` type conditional checks amongst various functions where none were provided -- old code that used the go-kit/log.Logger interface had several places where there were nil references when trying to use functions like `With()` to add keyvals on the new *slog.Logger type Signed-off-by: TJ Hoplock <t.hoplock@gmail.com>	1 year ago
Matthieu MOREL	ab64966e9d	fix: use "ErrorContains" or "EqualError" instead of "Contains(t, err.Error()" and "Equal(t, err.Error()" (#15094 ) * fix: use "ErrorContains" or "EqualError" instead of "Contains(t, err.Error()" and "Equal(t, err.Error()" --------- Signed-off-by: Matthieu MOREL <matthieu.morel35@gmail.com> Signed-off-by: Arve Knudsen <arve.knudsen@gmail.com> Co-authored-by: Arve Knudsen <arve.knudsen@gmail.com>	1 year ago
György Krajcsovits	b5479831b8	Unit test for regression in rate vs float and histogram mixup Signed-off-by: György Krajcsovits <gyorgy.krajcsovits@grafana.com>	1 year ago
Manik Rana	f1c57a95ed	change: No longer ingest OM _created as timeseries if feature-flag 'enable-ct-zero-ingestion' is enabled; fixed OM text CT conversion bug (#14738 ) * chore: revert TypeRequiresCT to private Signed-off-by: Manik Rana <manikrana54@gmail.com> * feat: init NewOpenMetricsParser with skipCT true Signed-off-by: Manik Rana <manikrana54@gmail.com> * refac: allow opt-in to OM CT ingestion Signed-off-by: Manik Rana <manikrana54@gmail.com> * chore: lint Signed-off-by: Manik Rana <manikrana54@gmail.com> * chore: use textparse interface to set om options Signed-off-by: Manik Rana <manikrana54@gmail.com> * fix: set skipOMSeries in test Signed-off-by: Manik Rana <manikrana54@gmail.com> * chore: gofumpt Signed-off-by: Manik Rana <manikrana54@gmail.com> * wip: add tests for OM CR parse Signed-off-by: Manik Rana <manikrana54@gmail.com> * chore: merge ct tests Signed-off-by: Manik Rana <manikrana54@gmail.com> * tests: add cases for OM text Signed-off-by: Manik Rana <manikrana54@gmail.com> * fix: check correct test cases Signed-off-by: Manik Rana <manikrana54@gmail.com> * chore: use both scrape protocols in config Signed-off-by: Manik Rana <manikrana54@gmail.com> * fix: fix inputs and output tests for OM Signed-off-by: Manik Rana <manikrana54@gmail.com> * chore: cleanup Signed-off-by: Manik Rana <manikrana54@gmail.com> * refac: rename skipOMSeries to skipOMCTSeries Co-authored-by: Arthur Silva Sens <arthursens2005@gmail.com> Signed-off-by: Manik Rana <Manikrana54@gmail.com> * fix: finish refac Signed-off-by: Manik Rana <manikrana54@gmail.com> * refac: move setup code outside test Signed-off-by: Manik Rana <manikrana54@gmail.com> * tests: verify _created lines create new metric in certain cases Signed-off-by: Manik Rana <manikrana54@gmail.com> * fix: post merge fixes Signed-off-by: Manik Rana <manikrana54@gmail.com> * chore: lint Signed-off-by: Manik Rana <manikrana54@gmail.com> * manager: Fixed CT OMText conversion bug; Refactored tests. Signed-off-by: bwplotka <bwplotka@gmail.com> * chore: lint Signed-off-by: Manik Rana <manikrana54@gmail.com> * chore: gofumpt Signed-off-by: Manik Rana <manikrana54@gmail.com> * chore: imports Signed-off-by: Manik Rana <manikrana54@gmail.com> --------- Signed-off-by: Manik Rana <manikrana54@gmail.com> Signed-off-by: Manik Rana <Manikrana54@gmail.com> Signed-off-by: bwplotka <bwplotka@gmail.com> Co-authored-by: Arthur Silva Sens <arthursens2005@gmail.com> Co-authored-by: bwplotka <bwplotka@gmail.com>	1 year ago
Bryan Boreham	b8e5b7cda9	[REFACTOR] PromQL: remove label_join and label_replace stubs These functions operate on whole series, not on samples, so they do not fit into the table of functions that return a Vector. Remove the stub entries that were left to help downstream users of the code identify what changed. We cannot remove the entries from the `FunctionCalls` map without breaking `TestFunctionList`, so put some nils in to keep it happy. Signed-off-by: Bryan Boreham <bjboreham@gmail.com>	1 year ago
Neeraj Gartia	8aef821e10	eval_info command Signed-off-by: Neeraj Gartia <neerajgartia211002@gmail.com>	1 year ago
Bryan Boreham	7f99d2930d	[BUGFIX] PromQL: make sort_by_label stable Go's sorting functions can re-order equal elements, so the strategy of sorting by the fallback ordering first does not always work. Pulling the fallback into the main comparison function is more reliable and more efficient. Signed-off-by: Bryan Boreham <bjboreham@gmail.com>	1 year ago
Jeanette Tan	4503145c8b	convert classic histograms to int nhcb where possible instead Signed-off-by: Jeanette Tan <jeanette.tan@grafana.com>	1 year ago
Jeanette Tan	62e7f0438d	implement basic conversion of classic to nhcb in scrape Signed-off-by: Jeanette Tan <jeanette.tan@grafana.com>	1 year ago
Arve Knudsen	c2bbabb4a7	promql.Engine: Refactor vector selector evaluation into a method (#14900 ) * PromQL.Engine: Refactor Matrix expansion into a method Add utility method promql.evaluator.expandSeriesToMatrix, for expanding a slice of storage.Series into a promql.Matrix. Signed-off-by: Arve Knudsen <arve.knudsen@gmail.com> * Rename to generateMatrix Rename evaluator.expandSeriesToMatrix into generateMatrix, while also dropping the start, end, interval arguments since they are evaluator fields. Write more extensive method documentation. Signed-off-by: Arve Knudsen <arve.knudsen@gmail.com> * Rename to evalVectorSelector Rename to evalVectorSelector after discussing with @michahoffmann. Signed-off-by: Arve Knudsen <arve.knudsen@gmail.com> --------- Signed-off-by: Arve Knudsen <arve.knudsen@gmail.com>	1 year ago
Manik Rana	3fba6bcdfa	chore: remove unused code Signed-off-by: Manik Rana <manikrana54@gmail.com>	1 year ago
Jan Fajerski	96e5a94d29	promql: rename holt_winters to double_exponential_smoothing Signed-off-by: Jan Fajerski <jfajersk@redhat.com>	1 year ago
Björn Rabenstein	1639450172	Merge pull request #14821 from charleskorn/nh-negative-multiplication-division promql: correctly handle unary negation of native histograms and add tests for multiplication and division of native histograms by negative scalars Signed-off-by: Bryan Boreham <bjboreham@gmail.com>	1 year ago
beorn7	6fcd225aee	promql(native histograms): Introduce exponential interpolation 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>	1 year ago

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1180 Commits (bwplotka-patch-2)