prometheus/storage/storage.go
2016-02-03 10:39:34 +01:00

77 lines
3 KiB
Go

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