prometheus/retrieval/target.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 retrieval
import (
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"fmt"
"math/rand"
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"net/http"
"os"
"strings"
"sync"
"time"
"github.com/golang/glog"
"github.com/prometheus/client_golang/extraction"
"github.com/prometheus/client_golang/prometheus"
clientmodel "github.com/prometheus/client_golang/model"
"github.com/prometheus/prometheus/utility"
)
const (
// InstanceLabel is the label value used for the instance label.
InstanceLabel clientmodel.LabelName = "instance"
// ScrapeHealthMetricName is the metric name for the synthetic health
// variable.
scrapeHealthMetricName clientmodel.LabelValue = "up"
// ScrapeTimeMetricName is the metric name for the synthetic scrape duration
// variable.
scrapeDurationMetricName clientmodel.LabelValue = "scrape_duration_seconds"
// Constants for instrumentation.
namespace = "prometheus"
interval = "interval"
)
var (
localhostRepresentations = []string{"http://127.0.0.1", "http://localhost"}
targetIntervalLength = prometheus.NewSummaryVec(
prometheus.SummaryOpts{
Namespace: namespace,
Name: "target_interval_length_seconds",
Help: "Actual intervals between scrapes.",
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Objectives: map[float64]float64{0.01: 0.001, 0.05: 0.005, 0.5: 0.05, 0.90: 0.01, 0.99: 0.001},
},
[]string{interval},
)
)
func init() {
prometheus.MustRegister(targetIntervalLength)
}
// TargetState describes the state of a Target.
type TargetState int
func (t TargetState) String() string {
switch t {
case Unknown:
return "UNKNOWN"
case Alive:
return "ALIVE"
case Unreachable:
return "UNREACHABLE"
}
panic("unknown state")
}
const (
// Unknown is the state of a Target that has not been seen; we know
// nothing about it, except that it is on our docket for examination.
Unknown TargetState = iota
// Alive is the state of a Target that has been found and successfully
// queried.
Alive
// Unreachable is the state of a Target that was either historically
// found or not found and then determined to be unhealthy by either not
// responding or disappearing.
Unreachable
)
// A Target represents an endpoint that should be interrogated for metrics.
//
// The protocol described by this type will likely change in future iterations,
// as it offers no good support for aggregated targets and fan out. Thusly,
// it is likely that the current Target and target uses will be
// wrapped with some resolver type.
//
// For the future, the Target protocol will abstract away the exact means that
// metrics are retrieved and deserialized from the given instance to which it
// refers.
type Target interface {
// Return the last encountered scrape error, if any.
LastError() error
// Return the health of the target.
State() TargetState
// Return the last time a scrape was attempted.
LastScrape() time.Time
// The URL to which the Target corresponds. Out of all of the available
// points in this interface, this one is the best candidate to change given
// the ways to express the endpoint.
URL() string
// The URL as seen from other hosts. References to localhost are resolved
// to the address of the prometheus server.
GlobalURL() string
// Return the target's base labels.
BaseLabels() clientmodel.LabelSet
// SetBaseLabelsFrom queues a replacement of the current base labels by
// the labels of the given target. The method returns immediately after
// queuing. The actual replacement of the base labels happens
// asynchronously (but most likely before the next scrape for the target
// begins).
SetBaseLabelsFrom(Target)
// Scrape target at the specified interval.
RunScraper(extraction.Ingester, time.Duration)
// Stop scraping, synchronous.
StopScraper()
}
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// target is a Target that refers to a singular HTTP or HTTPS endpoint.
type target struct {
// The current health state of the target.
state TargetState
// The last encountered scrape error, if any.
lastError error
// The last time a scrape was attempted.
lastScrape time.Time
// Closing scraperStopping signals that scraping should stop.
scraperStopping chan struct{}
// Closing scraperStopped signals that scraping has been stopped.
scraperStopped chan struct{}
// Channel to queue base labels to be replaced.
newBaseLabels chan clientmodel.LabelSet
url string
// What is the deadline for the HTTP or HTTPS against this endpoint.
Deadline time.Duration
// Any base labels that are added to this target and its metrics.
baseLabels clientmodel.LabelSet
// The HTTP client used to scrape the target's endpoint.
httpClient *http.Client
// Mutex protects lastError, lastScrape, state, and baseLabels. Writing
// the above must only happen in the goroutine running the RunScraper
// loop, and it must happen under the lock. In that way, no mutex lock
// is required for reading the above in the goroutine running the
// RunScraper loop, but only for reading in other goroutines.
sync.Mutex
}
// NewTarget creates a reasonably configured target for querying.
func NewTarget(url string, deadline time.Duration, baseLabels clientmodel.LabelSet) Target {
target := &target{
url: url,
Deadline: deadline,
baseLabels: baseLabels,
httpClient: utility.NewDeadlineClient(deadline),
scraperStopping: make(chan struct{}),
scraperStopped: make(chan struct{}),
newBaseLabels: make(chan clientmodel.LabelSet, 1),
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}
return target
}
func (t *target) recordScrapeHealth(ingester extraction.Ingester, timestamp clientmodel.Timestamp, healthy bool, scrapeDuration time.Duration) {
healthMetric := clientmodel.Metric{}
durationMetric := clientmodel.Metric{}
for label, value := range t.baseLabels {
healthMetric[label] = value
durationMetric[label] = value
}
healthMetric[clientmodel.MetricNameLabel] = clientmodel.LabelValue(scrapeHealthMetricName)
durationMetric[clientmodel.MetricNameLabel] = clientmodel.LabelValue(scrapeDurationMetricName)
healthMetric[InstanceLabel] = clientmodel.LabelValue(t.URL())
durationMetric[InstanceLabel] = clientmodel.LabelValue(t.URL())
healthValue := clientmodel.SampleValue(0)
if healthy {
healthValue = clientmodel.SampleValue(1)
}
healthSample := &clientmodel.Sample{
Metric: healthMetric,
Timestamp: timestamp,
Value: healthValue,
}
durationSample := &clientmodel.Sample{
Metric: durationMetric,
Timestamp: timestamp,
Value: clientmodel.SampleValue(float64(scrapeDuration) / float64(time.Second)),
}
ingester.Ingest(clientmodel.Samples{healthSample, durationSample})
}
// RunScraper implements Target.
func (t *target) RunScraper(ingester extraction.Ingester, interval time.Duration) {
defer func() {
// Need to drain t.newBaseLabels to not make senders block during shutdown.
for {
select {
case <-t.newBaseLabels:
// Do nothing.
default:
close(t.scraperStopped)
return
}
}
}()
jitterTimer := time.NewTimer(time.Duration(float64(interval) * rand.Float64()))
select {
case <-jitterTimer.C:
case <-t.scraperStopping:
jitterTimer.Stop()
return
}
jitterTimer.Stop()
ticker := time.NewTicker(interval)
defer ticker.Stop()
t.Lock() // Writing t.lastScrape requires the lock.
t.lastScrape = time.Now()
t.Unlock()
t.scrape(ingester)
// Explanation of the contraption below:
//
// In case t.newBaseLabels or t.scraperStopping have something to receive,
// we want to read from those channels rather than starting a new scrape
// (which might take very long). That's why the outer select has no
// ticker.C. Should neither t.newBaseLabels nor t.scraperStopping have
// anything to receive, we go into the inner select, where ticker.C is
// in the mix.
for {
select {
case newBaseLabels := <-t.newBaseLabels:
t.Lock() // Writing t.baseLabels requires the lock.
t.baseLabels = newBaseLabels
t.Unlock()
case <-t.scraperStopping:
return
default:
select {
case newBaseLabels := <-t.newBaseLabels:
t.Lock() // Writing t.baseLabels requires the lock.
t.baseLabels = newBaseLabels
t.Unlock()
case <-t.scraperStopping:
return
case <-ticker.C:
targetIntervalLength.WithLabelValues(interval.String()).Observe(float64(time.Since(t.lastScrape) / time.Second))
t.Lock() // Write t.lastScrape requires locking.
t.lastScrape = time.Now()
t.Unlock()
t.scrape(ingester)
}
}
}
}
// StopScraper implements Target.
func (t *target) StopScraper() {
close(t.scraperStopping)
<-t.scraperStopped
}
const acceptHeader = `application/vnd.google.protobuf;proto=io.prometheus.client.MetricFamily;encoding=delimited;q=0.7,text/plain;version=0.0.4;q=0.3,application/json;schema="prometheus/telemetry";version=0.0.2;q=0.2,*/*;q=0.1`
func (t *target) scrape(ingester extraction.Ingester) (err error) {
timestamp := clientmodel.Now()
defer func(start time.Time) {
t.Lock() // Writing t.state and t.lastError requires the lock.
if err == nil {
t.state = Alive
} else {
t.state = Unreachable
}
t.lastError = err
t.Unlock()
t.recordScrapeHealth(ingester, timestamp, err == nil, time.Since(start))
}(time.Now())
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req, err := http.NewRequest("GET", t.URL(), nil)
if err != nil {
panic(err)
}
req.Header.Add("Accept", acceptHeader)
resp, err := t.httpClient.Do(req)
if err != nil {
return err
}
defer resp.Body.Close()
if resp.StatusCode != http.StatusOK {
return fmt.Errorf("server returned HTTP status %s", resp.Status)
}
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processor, err := extraction.ProcessorForRequestHeader(resp.Header)
if err != nil {
return err
}
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baseLabels := clientmodel.LabelSet{InstanceLabel: clientmodel.LabelValue(t.URL())}
for baseLabel, baseValue := range t.baseLabels {
baseLabels[baseLabel] = baseValue
}
i := &MergeLabelsIngester{
Labels: baseLabels,
CollisionPrefix: clientmodel.ExporterLabelPrefix,
Ingester: ingester,
}
processOptions := &extraction.ProcessOptions{
Timestamp: timestamp,
}
return processor.ProcessSingle(resp.Body, i, processOptions)
}
// LastError implements Target.
func (t *target) LastError() error {
t.Lock()
defer t.Unlock()
return t.lastError
}
// State implements Target.
func (t *target) State() TargetState {
t.Lock()
defer t.Unlock()
return t.state
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}
// LastScrape implements Target.
func (t *target) LastScrape() time.Time {
t.Lock()
defer t.Unlock()
return t.lastScrape
}
// URL implements Target.
func (t *target) URL() string {
return t.url
}
// GlobalURL implements Target.
func (t *target) GlobalURL() string {
url := t.url
hostname, err := os.Hostname()
if err != nil {
glog.Warningf("Couldn't get hostname: %s, returning target.URL()", err)
return url
}
for _, localhostRepresentation := range localhostRepresentations {
url = strings.Replace(url, localhostRepresentation, fmt.Sprintf("http://%s", hostname), -1)
}
return url
}
// BaseLabels implements Target.
func (t *target) BaseLabels() clientmodel.LabelSet {
t.Lock()
defer t.Unlock()
return t.baseLabels
}
// SetBaseLabelsFrom implements Target.
func (t *target) SetBaseLabelsFrom(newTarget Target) {
if t.URL() != newTarget.URL() {
panic("targets don't refer to the same endpoint")
}
t.newBaseLabels <- newTarget.BaseLabels()
}