prometheus/storage/secondary.go
🌲 Harry 🌊 John 🏔 d5f6887294 Pass limit param as hint to storage.Querier
Signed-off-by: 🌲 Harry 🌊 John 🏔 <johrry@amazon.com>
2024-06-20 09:47:38 -07:00

110 lines
4 KiB
Go

// Copyright 2017 The Prometheus Authors
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package storage
import (
"context"
"sync"
"github.com/prometheus/prometheus/model/labels"
"github.com/prometheus/prometheus/util/annotations"
)
// secondaryQuerier is a wrapper that allows a querier to be treated in a best effort manner.
// This means that an error on any method returned by Querier except Close will be returned as a warning,
// and the result will be empty.
//
// Additionally, Querier ensures that if ANY SeriesSet returned by this querier's Select failed on an initial Next,
// All other SeriesSet will be return no response as well. This ensures consistent partial response strategy, where you
// have either full results or none from each secondary Querier.
// NOTE: This works well only for implementations that only fail during first Next() (e.g fetch from network). If implementation fails
// during further iterations, set will panic. If Select is invoked after first Next of any returned SeriesSet, querier will panic.
//
// Not go-routine safe.
// NOTE: Prometheus treats all remote storages as secondary / best effort.
type secondaryQuerier struct {
genericQuerier
once sync.Once
done bool
asyncSets []genericSeriesSet
}
func newSecondaryQuerierFrom(q Querier) genericQuerier {
return &secondaryQuerier{genericQuerier: newGenericQuerierFrom(q)}
}
func newSecondaryQuerierFromChunk(cq ChunkQuerier) genericQuerier {
return &secondaryQuerier{genericQuerier: newGenericQuerierFromChunk(cq)}
}
func (s *secondaryQuerier) LabelValues(ctx context.Context, name string, hints *LabelHints, matchers ...*labels.Matcher) ([]string, annotations.Annotations, error) {
vals, w, err := s.genericQuerier.LabelValues(ctx, name, hints, matchers...)
if err != nil {
return nil, w.Add(err), nil
}
return vals, w, nil
}
func (s *secondaryQuerier) LabelNames(ctx context.Context, hints *LabelHints, matchers ...*labels.Matcher) ([]string, annotations.Annotations, error) {
names, w, err := s.genericQuerier.LabelNames(ctx, hints, matchers...)
if err != nil {
return nil, w.Add(err), nil
}
return names, w, nil
}
func (s *secondaryQuerier) Select(ctx context.Context, sortSeries bool, hints *SelectHints, matchers ...*labels.Matcher) genericSeriesSet {
if s.done {
panic("secondaryQuerier: Select invoked after first Next of any returned SeriesSet was done")
}
s.asyncSets = append(s.asyncSets, s.genericQuerier.Select(ctx, sortSeries, hints, matchers...))
curr := len(s.asyncSets) - 1
return &lazyGenericSeriesSet{init: func() (genericSeriesSet, bool) {
s.once.Do(func() {
// At first init invocation we iterate over all async sets and ensure its Next() returns some value without
// errors. This is to ensure we support consistent partial failures.
for i, set := range s.asyncSets {
if set.Next() {
continue
}
ws := set.Warnings()
if err := set.Err(); err != nil {
// One of the sets failed, ensure current one returning errors as warnings, and rest of the sets return nothing.
// (All or nothing logic).
s.asyncSets[curr] = warningsOnlySeriesSet(ws.Add(err))
for i := range s.asyncSets {
if curr == i {
continue
}
s.asyncSets[i] = noopGenericSeriesSet{}
}
break
}
// Exhausted set.
s.asyncSets[i] = warningsOnlySeriesSet(ws)
}
s.done = true
})
switch s.asyncSets[curr].(type) {
case warningsOnlySeriesSet, noopGenericSeriesSet:
return s.asyncSets[curr], false
default:
return s.asyncSets[curr], true
}
}}
}