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Return annotations (warnings and infos) from PromQL queries This generalizes the warnings we have already used before (but only for problems with remote read) as "annotations". Annotations can be warnings or infos (the latter could be false positives). We do not treat them different in the API for now and return them all as "warnings". It would be easy to distinguish them and return infos separately, should that appear useful in the future. The new annotations are then used to create a lot of warnings or infos during PromQL evaluations. Partially these are things we have wanted for a long time (e.g. inform the user that they have applied `rate` to a metric that doesn't look like a counter), but the new native histograms have created even more needs for those annotations (e.g. if a query tries to aggregate float numbers with histograms). The annotations added here are not yet complete. A prominent example would be a warning about a range too short for a rate calculation. But such a warnings is more tricky to create with good fidelity and we will tackle it later. Another TODO is to take annotations into account when evaluating recording rules. --------- Signed-off-by: Jeanette Tan <jeanette.tan@grafana.com>
110 lines
3.9 KiB
Go
110 lines
3.9 KiB
Go
// Copyright 2017 The Prometheus Authors
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package storage
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import (
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"context"
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"sync"
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"github.com/prometheus/prometheus/model/labels"
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"github.com/prometheus/prometheus/util/annotations"
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)
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// secondaryQuerier is a wrapper that allows a querier to be treated in a best effort manner.
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// This means that an error on any method returned by Querier except Close will be returned as a warning,
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// and the result will be empty.
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//
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// Additionally, Querier ensures that if ANY SeriesSet returned by this querier's Select failed on an initial Next,
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// All other SeriesSet will be return no response as well. This ensures consistent partial response strategy, where you
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// have either full results or none from each secondary Querier.
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// NOTE: This works well only for implementations that only fail during first Next() (e.g fetch from network). If implementation fails
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// during further iterations, set will panic. If Select is invoked after first Next of any returned SeriesSet, querier will panic.
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//
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// Not go-routine safe.
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// NOTE: Prometheus treats all remote storages as secondary / best effort.
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type secondaryQuerier struct {
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genericQuerier
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once sync.Once
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done bool
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asyncSets []genericSeriesSet
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}
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func newSecondaryQuerierFrom(q Querier) genericQuerier {
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return &secondaryQuerier{genericQuerier: newGenericQuerierFrom(q)}
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}
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func newSecondaryQuerierFromChunk(cq ChunkQuerier) genericQuerier {
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return &secondaryQuerier{genericQuerier: newGenericQuerierFromChunk(cq)}
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}
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func (s *secondaryQuerier) LabelValues(ctx context.Context, name string, matchers ...*labels.Matcher) ([]string, annotations.Annotations, error) {
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vals, w, err := s.genericQuerier.LabelValues(ctx, name, matchers...)
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if err != nil {
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return nil, w.Add(err), nil
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}
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return vals, w, nil
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}
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func (s *secondaryQuerier) LabelNames(ctx context.Context, matchers ...*labels.Matcher) ([]string, annotations.Annotations, error) {
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names, w, err := s.genericQuerier.LabelNames(ctx, matchers...)
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if err != nil {
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return nil, w.Add(err), nil
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}
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return names, w, nil
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}
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func (s *secondaryQuerier) Select(ctx context.Context, sortSeries bool, hints *SelectHints, matchers ...*labels.Matcher) genericSeriesSet {
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if s.done {
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panic("secondaryQuerier: Select invoked after first Next of any returned SeriesSet was done")
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}
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s.asyncSets = append(s.asyncSets, s.genericQuerier.Select(ctx, sortSeries, hints, matchers...))
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curr := len(s.asyncSets) - 1
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return &lazyGenericSeriesSet{init: func() (genericSeriesSet, bool) {
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s.once.Do(func() {
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// At first init invocation we iterate over all async sets and ensure its Next() returns some value without
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// errors. This is to ensure we support consistent partial failures.
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for i, set := range s.asyncSets {
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if set.Next() {
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continue
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}
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ws := set.Warnings()
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if err := set.Err(); err != nil {
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// One of the sets failed, ensure current one returning errors as warnings, and rest of the sets return nothing.
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// (All or nothing logic).
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s.asyncSets[curr] = warningsOnlySeriesSet(ws.Add(err))
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for i := range s.asyncSets {
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if curr == i {
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continue
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}
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s.asyncSets[i] = noopGenericSeriesSet{}
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}
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break
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}
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// Exhausted set.
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s.asyncSets[i] = warningsOnlySeriesSet(ws)
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}
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s.done = true
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})
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switch s.asyncSets[curr].(type) {
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case warningsOnlySeriesSet, noopGenericSeriesSet:
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return s.asyncSets[curr], false
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default:
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return s.asyncSets[curr], true
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}
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}}
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}
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