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77 lines
3 KiB
Go
77 lines
3 KiB
Go
// Copyright 2015 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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"github.com/prometheus/common/model"
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)
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// SampleAppender is the interface to append samples to both, local and remote
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// storage. All methods are goroutine-safe.
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type SampleAppender interface {
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// Append appends a sample to the underlying storage. Depending on the
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// storage implementation, there are different guarantees for the fate
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// of the sample after Append has returned. Remote storage
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// implementation will simply drop samples if they cannot keep up with
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// sending samples. Local storage implementations will only drop metrics
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// upon unrecoverable errors.
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Append(*model.Sample) error
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// NeedsThrottling returns true if the underlying storage wishes to not
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// receive any more samples. Append will still work but might lead to
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// undue resource usage. It is recommended to call NeedsThrottling once
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// before an upcoming batch of Append calls (e.g. a full scrape of a
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// target or the evaluation of a rule group) and only proceed with the
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// batch if NeedsThrottling returns false. In that way, the result of a
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// scrape or of an evaluation of a rule group will always be appended
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// completely or not at all, and the work of scraping or evaluation will
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// not be performed in vain. Also, a call of NeedsThrottling is
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// potentially expensive, so limiting the number of calls is reasonable.
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//
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// Only SampleAppenders for which it is considered critical to receive
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// each and every sample should ever return true. SampleAppenders that
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// tolerate not receiving all samples should always return false and
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// instead drop samples as they see fit to avoid overload.
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NeedsThrottling() bool
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}
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// Fanout is a SampleAppender that appends every sample to each SampleAppender
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// in its list.
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type Fanout []SampleAppender
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// Append implements SampleAppender. It appends the provided sample to all
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// SampleAppenders in the Fanout slice and waits for each append to complete
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// before proceeding with the next.
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// If any of the SampleAppenders returns an error, the first one is returned
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// at the end.
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func (f Fanout) Append(s *model.Sample) error {
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var err error
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for _, a := range f {
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if e := a.Append(s); e != nil && err == nil {
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err = e
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}
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}
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return err
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}
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// NeedsThrottling returns true if at least one of the SampleAppenders in the
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// Fanout slice is throttled.
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func (f Fanout) NeedsThrottling() bool {
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for _, a := range f {
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if a.NeedsThrottling() {
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return true
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}
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}
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return false
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}
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