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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 (
"sync"
"time"
"github.com/prometheus/client_golang/prometheus"
"github.com/prometheus/common/log"
"github.com/prometheus/common/model"
)
// String constants for instrumentation.
const (
namespace = "prometheus"
subsystem = "remote_storage"
queue = "queue"
)
var (
sentSamplesTotal = prometheus.NewCounterVec(
prometheus.CounterOpts{
Namespace: namespace,
Subsystem: subsystem,
Name: "sent_samples_total",
Help: "Total number of processed samples sent to remote storage.",
},
[]string{queue},
)
failedSamplesTotal = prometheus.NewCounterVec(
prometheus.CounterOpts{
Namespace: namespace,
Subsystem: subsystem,
Name: "failed_samples_total",
Help: "Total number of processed samples which failed on send to remote storage.",
},
[]string{queue},
)
droppedSamplesTotal = prometheus.NewCounterVec(
prometheus.CounterOpts{
Namespace: namespace,
Subsystem: subsystem,
Name: "dropped_samples_total",
Help: "Total number of samples which were dropped due to the queue being full.",
},
[]string{queue},
)
sentBatchDuration = prometheus.NewHistogramVec(
prometheus.HistogramOpts{
Namespace: namespace,
Subsystem: subsystem,
Name: "sent_batch_duration_seconds",
Help: "Duration of sample batch send calls to the remote storage.",
Buckets: prometheus.DefBuckets,
},
[]string{queue},
)
queueLength = prometheus.NewGaugeVec(
prometheus.GaugeOpts{
Namespace: namespace,
Subsystem: subsystem,
Name: "queue_length",
Help: "The number of processed samples queued to be sent to the remote storage.",
},
[]string{queue},
)
queueCapacity = prometheus.NewGaugeVec(
prometheus.GaugeOpts{
Namespace: namespace,
Subsystem: subsystem,
Name: "queue_capacity",
Help: "The capacity of the queue of samples to be sent to the remote storage.",
},
[]string{queue},
)
)
func init() {
prometheus.MustRegister(sentSamplesTotal)
prometheus.MustRegister(failedSamplesTotal)
prometheus.MustRegister(droppedSamplesTotal)
prometheus.MustRegister(sentBatchDuration)
prometheus.MustRegister(queueLength)
prometheus.MustRegister(queueCapacity)
}
// 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
}
type StorageQueueManagerConfig struct {
QueueCapacity int // Number of samples to buffer per shard before we start dropping them.
Shards int // Number of shards, i.e. amount of concurrency.
MaxSamplesPerSend int // Maximum number of samples per send.
BatchSendDeadline time.Duration // Maximum time sample will wait in buffer.
}
var defaultConfig = StorageQueueManagerConfig{
QueueCapacity: 100 * 1024 / 10,
Shards: 10,
MaxSamplesPerSend: 100,
BatchSendDeadline: 5 * time.Second,
}
// StorageQueueManager manages a queue of samples to be sent to the Storage
// indicated by the provided StorageClient.
type StorageQueueManager struct {
cfg StorageQueueManagerConfig
tsdb StorageClient
shards []chan *model.Sample
wg sync.WaitGroup
done chan struct{}
queueName string
}
// NewStorageQueueManager builds a new StorageQueueManager.
func NewStorageQueueManager(tsdb StorageClient, cfg *StorageQueueManagerConfig) *StorageQueueManager {
if cfg == nil {
cfg = &defaultConfig
}
shards := make([]chan *model.Sample, cfg.Shards)
for i := 0; i < cfg.Shards; i++ {
shards[i] = make(chan *model.Sample, cfg.QueueCapacity)
}
t := &StorageQueueManager{
cfg: *cfg,
tsdb: tsdb,
shards: shards,
done: make(chan struct{}),
queueName: tsdb.Name(),
}
queueCapacity.WithLabelValues(t.queueName).Set(float64(t.cfg.QueueCapacity))
t.wg.Add(cfg.Shards)
return t
}
// 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 {
fp := s.Metric.FastFingerprint()
shard := uint64(fp) % uint64(t.cfg.Shards)
select {
case t.shards[shard] <- s:
queueLength.WithLabelValues(t.queueName).Inc()
default:
droppedSamplesTotal.WithLabelValues(t.queueName).Inc()
log.Warn("Remote storage queue full, discarding sample.")
}
return nil
}
// NeedsThrottling implements storage.SampleAppender. It will always return
// false as a remote storage drops samples on the floor if backlogging instead
// of asking for throttling.
func (*StorageQueueManager) NeedsThrottling() bool {
return false
}
// Start the queue manager sending samples to the remote storage.
// Does not block.
func (t *StorageQueueManager) Start() {
for i := 0; i < t.cfg.Shards; i++ {
go t.runShard(i)
}
}
// Stop stops sending samples to the remote storage and waits for pending
// sends to complete.
func (t *StorageQueueManager) Stop() {
log.Infof("Stopping remote storage...")
for _, shard := range t.shards {
close(shard)
}
t.wg.Wait()
log.Info("Remote storage stopped.")
}
func (t *StorageQueueManager) runShard(i int) {
defer t.wg.Done()
shard := t.shards[i]
// 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.
pendingSamples := model.Samples{}
for {
select {
case s, ok := <-shard:
if !ok {
if len(pendingSamples) > 0 {
log.Infof("Flushing %d samples to remote storage...", len(pendingSamples))
t.sendSamples(pendingSamples)
log.Infof("Done flushing.")
}
return
}
queueLength.WithLabelValues(t.queueName).Dec()
pendingSamples = append(pendingSamples, s)
for len(pendingSamples) >= t.cfg.MaxSamplesPerSend {
t.sendSamples(pendingSamples[:t.cfg.MaxSamplesPerSend])
pendingSamples = pendingSamples[t.cfg.MaxSamplesPerSend:]
}
case <-time.After(t.cfg.BatchSendDeadline):
if len(pendingSamples) > 0 {
t.sendSamples(pendingSamples)
pendingSamples = pendingSamples[:0]
}
}
}
}
func (t *StorageQueueManager) sendSamples(s model.Samples) {
// 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()
if err != nil {
log.Warnf("error sending %d samples to remote storage: %s", len(s), err)
failedSamplesTotal.WithLabelValues(t.queueName).Add(float64(len(s)))
} else {
sentSamplesTotal.WithLabelValues(t.queueName).Add(float64(len(s)))
}
sentBatchDuration.WithLabelValues(t.queueName).Observe(duration)
}