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queue_manager.go
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/
queue_manager.go
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// Copyright 2013 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 remote
import (
"time"
"github.com/prometheus/client_golang/prometheus"
"github.com/prometheus/common/log"
"github.com/prometheus/common/model"
)
const (
// The maximum number of concurrent send requests to the remote storage.
maxConcurrentSends = 10
// The maximum number of samples to fit into a single request to the remote storage.
maxSamplesPerSend = 100
// The deadline after which to send queued samples even if the maximum batch
// size has not been reached.
batchSendDeadline = 5 * time.Second
)
// String constants for instrumentation.
const (
namespace = "prometheus"
subsystem = "remote_storage"
result = "result"
success = "success"
failure = "failure"
dropped = "dropped"
)
// StorageClient defines an interface for sending a batch of samples to an
// external timeseries database.
type StorageClient interface {
// Store stores the given samples in the remote storage.
Store(model.Samples) error
// Name identifies the remote storage implementation.
Name() string
}
// StorageQueueManager manages a queue of samples to be sent to the Storage
// indicated by the provided StorageClient.
type StorageQueueManager struct {
tsdb StorageClient
queue chan *model.Sample
pendingSamples model.Samples
sendSemaphore chan bool
drained chan bool
samplesCount *prometheus.CounterVec
sendLatency prometheus.Summary
failedBatches prometheus.Counter
failedSamples prometheus.Counter
queueLength prometheus.Gauge
queueCapacity prometheus.Metric
}
// NewStorageQueueManager builds a new StorageQueueManager.
func NewStorageQueueManager(tsdb StorageClient, queueCapacity int) *StorageQueueManager {
constLabels := prometheus.Labels{
"type": tsdb.Name(),
}
return &StorageQueueManager{
tsdb: tsdb,
queue: make(chan *model.Sample, queueCapacity),
sendSemaphore: make(chan bool, maxConcurrentSends),
drained: make(chan bool),
samplesCount: prometheus.NewCounterVec(
prometheus.CounterOpts{
Namespace: namespace,
Subsystem: subsystem,
Name: "sent_samples_total",
Help: "Total number of processed samples to be sent to remote storage.",
ConstLabels: constLabels,
},
[]string{result},
),
sendLatency: prometheus.NewSummary(prometheus.SummaryOpts{
Namespace: namespace,
Subsystem: subsystem,
Name: "send_latency_seconds",
Help: "Latency quantiles for sending sample batches to the remote storage.",
ConstLabels: constLabels,
}),
failedBatches: prometheus.NewCounter(prometheus.CounterOpts{
Namespace: namespace,
Subsystem: subsystem,
Name: "failed_batches_total",
Help: "Total number of sample batches that encountered an error while being sent to the remote storage.",
ConstLabels: constLabels,
}),
failedSamples: prometheus.NewCounter(prometheus.CounterOpts{
Namespace: namespace,
Subsystem: subsystem,
Name: "failed_samples_total",
Help: "Total number of samples that encountered an error while being sent to the remote storage.",
ConstLabels: constLabels,
}),
queueLength: prometheus.NewGauge(prometheus.GaugeOpts{
Namespace: namespace,
Subsystem: subsystem,
Name: "queue_length",
Help: "The number of processed samples queued to be sent to the remote storage.",
ConstLabels: constLabels,
}),
queueCapacity: prometheus.MustNewConstMetric(
prometheus.NewDesc(
prometheus.BuildFQName(namespace, subsystem, "queue_capacity"),
"The capacity of the queue of samples to be sent to the remote storage.",
nil,
constLabels,
),
prometheus.GaugeValue,
float64(queueCapacity),
),
}
}
// Append queues a sample to be sent to the remote storage. It drops the
// sample on the floor if the queue is full.
// Always returns nil.
func (t *StorageQueueManager) Append(s *model.Sample) error {
select {
case t.queue <- s:
default:
t.samplesCount.WithLabelValues(dropped).Inc()
log.Warn("Remote storage queue full, discarding sample.")
}
return nil
}
// Stop stops sending samples to the remote storage and waits for pending
// sends to complete.
func (t *StorageQueueManager) Stop() {
log.Infof("Stopping remote storage...")
close(t.queue)
<-t.drained
for i := 0; i < maxConcurrentSends; i++ {
t.sendSemaphore <- true
}
log.Info("Remote storage stopped.")
}
// Describe implements prometheus.Collector.
func (t *StorageQueueManager) Describe(ch chan<- *prometheus.Desc) {
t.samplesCount.Describe(ch)
t.sendLatency.Describe(ch)
ch <- t.failedBatches.Desc()
ch <- t.failedSamples.Desc()
ch <- t.queueLength.Desc()
ch <- t.queueCapacity.Desc()
}
// Collect implements prometheus.Collector.
func (t *StorageQueueManager) Collect(ch chan<- prometheus.Metric) {
t.samplesCount.Collect(ch)
t.sendLatency.Collect(ch)
t.queueLength.Set(float64(len(t.queue)))
ch <- t.failedBatches
ch <- t.failedSamples
ch <- t.queueLength
ch <- t.queueCapacity
}
func (t *StorageQueueManager) sendSamples(s model.Samples) {
t.sendSemaphore <- true
go func() {
defer func() {
<-t.sendSemaphore
}()
// Samples are sent to the remote storage on a best-effort basis. If a
// sample isn't sent correctly the first time, it's simply dropped on the
// floor.
begin := time.Now()
err := t.tsdb.Store(s)
duration := time.Since(begin).Seconds()
labelValue := success
if err != nil {
log.Warnf("error sending %d samples to remote storage: %s", len(s), err)
labelValue = failure
t.failedBatches.Inc()
t.failedSamples.Add(float64(len(s)))
}
t.samplesCount.WithLabelValues(labelValue).Add(float64(len(s)))
t.sendLatency.Observe(duration)
}()
}
// Run continuously sends samples to the remote storage.
func (t *StorageQueueManager) Run() {
defer func() {
close(t.drained)
}()
// Send batches of at most maxSamplesPerSend samples to the remote storage.
// If we have fewer samples than that, flush them out after a deadline
// anyways.
for {
select {
case s, ok := <-t.queue:
if !ok {
log.Infof("Flushing %d samples to remote storage...", len(t.pendingSamples))
t.flush()
log.Infof("Done flushing.")
return
}
t.pendingSamples = append(t.pendingSamples, s)
for len(t.pendingSamples) >= maxSamplesPerSend {
t.sendSamples(t.pendingSamples[:maxSamplesPerSend])
t.pendingSamples = t.pendingSamples[maxSamplesPerSend:]
}
case <-time.After(batchSendDeadline):
t.flush()
}
}
}
// Flush flushes remaining queued samples.
func (t *StorageQueueManager) flush() {
if len(t.pendingSamples) > 0 {
t.sendSamples(t.pendingSamples)
}
t.pendingSamples = t.pendingSamples[:0]
}