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ec08c9a391
This gives up on the idea to communicate throuh the Append() call (by either not returning as it is now or returning an error as suggested/explored elsewhere). Here I have added a Throttled() call, which has the advantage that it can be called before a whole _batch_ of Append()'s. Scrapes will happen completely or not at all. Same for rule group evaluations. That's a highly desired behavior (as discussed elsewhere). The code is even simpler now as the whole ingestion buffer could be removed. Logging of throttled mode has been streamlined and will create at most one message per minute.
72 lines
2.9 KiB
Go
72 lines
2.9 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. Reporting any errors is done via metrics
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// and logs and not the concern of the caller.
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Append(*model.Sample)
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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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func (f Fanout) Append(s *model.Sample) {
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for _, a := range f {
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a.Append(s)
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}
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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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