prometheus

Commit Graph

Author	SHA1	Message	Date
Jack Neely	896f951e68	Force buckets in a histogram to be monotonic for quantile estimation (#2610 ) * Force buckets in a histogram to be monotonic for quantile estimation The assumption that bucket counts increase monotonically with increasing upperBound may be violated during: * Recording rule evaluation of histogram_quantile, especially when rate() has been applied to the underlying bucket timeseries. * Evaluation of histogram_quantile computed over federated bucket timeseries, especially when rate() has been applied This is because scraped data is not made available to RR evalution or federation atomically, so some buckets are computed with data from the N most recent scrapes, but the other buckets are missing the most recent observations. Monotonicity is usually guaranteed because if a bucket with upper bound u1 has count c1, then any bucket with a higher upper bound u > u1 must have counted all c1 observations and perhaps more, so that c >= c1. Randomly interspersed partial sampling breaks that guarantee, and rate() exacerbates it. Specifically, suppose bucket le=1000 has a count of 10 from 4 samples but the bucket with le=2000 has a count of 7, from 3 samples. The monotonicity is broken. It is exacerbated by rate() because under normal operation, cumulative counting of buckets will cause the bucket counts to diverge such that small differences from missing samples are not a problem. rate() removes this divergence.) bucketQuantile depends on that monotonicity to do a binary search for the bucket with the qth percentile count, so breaking the monotonicity guarantee causes bucketQuantile() to return undefined (nonsense) results. As a somewhat hacky solution until the Prometheus project is ready to accept the changes required to make scrapes atomic, we calculate the "envelope" of the histogram buckets, essentially removing any decreases in the count between successive buckets. * Fix up comment docs for ensureMonotonic * ensureMonotonic: Use switch statement Use switch statement rather than if/else for better readability. Process the most frequent cases first.	8 years ago
Brian Brazil	0303ccc6a7	Add quantile aggregator.	8 years ago
Brian Brazil	15f9fe0a45	Factor out quantile fucntion.	8 years ago
Fabian Reinartz	d6b8da8d43	Switch promql types to common/model	9 years ago
Fabian Reinartz	306e8468a0	Switch from client_golang/model to common/model	9 years ago
Brian Brazil	f34de493d5	Add increase() function, to replace delta(..., 1). This calculates how much a counter increases over a given period of time, which is the area under the curve of it's rate. increase(x[5m]) is equivilent to rate(x[5m]) * 300.	10 years ago
Fabian Reinartz	5602328c7c	Refactor query evaluation. This copies the evaluation logic from the current rules/ package. The new engine handles the execution process from query string to final result. It provides query timeout and cancellation and general flexibility for future changes. functions.go: Add evaluation implementation. Slight changes to in/out data but not to the processing logic. quantile.go: No changes. analyzer.go: No changes. engine.go: Actually new part. Mainly consists of evaluation methods which were not changed. setup_test.go: Copy of rules/helpers_test.go to setup test storage. promql_test.go: Copy of rules/rules_test.go.	10 years ago
Brian Brazil	941f585164	Avoid +InfYs and similar, just display +Inf.	10 years ago
beorn7	9e85ab0eef	Apply the new signature/fingerprinting functions from client_golang. This requires the new version of client_golang (vendoring will follow in the next commit), which changes the fingerprinting for clientmodel.Metric.	10 years ago
beorn7	17443d288b	Avoid copying of the COWMetric if we already have the metric available.	10 years ago
beorn7	9e7c3e3bcd	Add the histogram_quantile function. Since we are now getting really deep into floating point calculation, the tests had to take into account the precision loss. Since the rule tests are based on direct line matching in the output, implementing the "almost equal" semantics was pretty cumbersome, but here we are.	10 years ago

7 Commits (29fff1eca43fa759c26fd3f86e17aaebb4818d77)