prometheus/retrieval/scrape.go

650 lines
16 KiB
Go

// Copyright 2016 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 (
"bufio"
"bytes"
"compress/gzip"
"fmt"
"io"
"net/http"
"sync"
"time"
"unsafe"
"github.com/prometheus/client_golang/prometheus"
"github.com/prometheus/common/log"
"github.com/prometheus/common/version"
"golang.org/x/net/context"
"golang.org/x/net/context/ctxhttp"
"github.com/prometheus/prometheus/config"
"github.com/prometheus/prometheus/pkg/labels"
"github.com/prometheus/prometheus/pkg/textparse"
"github.com/prometheus/prometheus/pkg/timestamp"
"github.com/prometheus/prometheus/storage"
"github.com/prometheus/prometheus/util/httputil"
)
const (
scrapeHealthMetricName = "up"
scrapeDurationMetricName = "scrape_duration_seconds"
scrapeSamplesMetricName = "scrape_samples_scraped"
samplesPostRelabelMetricName = "scrape_samples_post_metric_relabeling"
)
var (
targetIntervalLength = prometheus.NewSummaryVec(
prometheus.SummaryOpts{
Name: "prometheus_target_interval_length_seconds",
Help: "Actual intervals between scrapes.",
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"},
)
targetSkippedScrapes = prometheus.NewCounter(
prometheus.CounterOpts{
Name: "prometheus_target_skipped_scrapes_total",
Help: "Total number of scrapes that were skipped because the metric storage was throttled.",
},
)
targetReloadIntervalLength = prometheus.NewSummaryVec(
prometheus.SummaryOpts{
Name: "prometheus_target_reload_length_seconds",
Help: "Actual interval to reload the scrape pool with a given configuration.",
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"},
)
targetSyncIntervalLength = prometheus.NewSummaryVec(
prometheus.SummaryOpts{
Name: "prometheus_target_sync_length_seconds",
Help: "Actual interval to sync the scrape pool.",
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{"scrape_job"},
)
targetScrapePoolSyncsCounter = prometheus.NewCounterVec(
prometheus.CounterOpts{
Name: "prometheus_target_scrape_pool_sync_total",
Help: "Total number of syncs that were executed on a scrape pool.",
},
[]string{"scrape_job"},
)
targetScrapeSampleLimit = prometheus.NewCounter(
prometheus.CounterOpts{
Name: "prometheus_target_scrapes_exceeded_sample_limit_total",
Help: "Total number of scrapes that hit the sample limit and were rejected.",
},
)
)
func init() {
prometheus.MustRegister(targetIntervalLength)
prometheus.MustRegister(targetSkippedScrapes)
prometheus.MustRegister(targetReloadIntervalLength)
prometheus.MustRegister(targetSyncIntervalLength)
prometheus.MustRegister(targetScrapePoolSyncsCounter)
prometheus.MustRegister(targetScrapeSampleLimit)
}
// scrapePool manages scrapes for sets of targets.
type scrapePool struct {
appendable Appendable
ctx context.Context
mtx sync.RWMutex
config *config.ScrapeConfig
client *http.Client
// Targets and loops must always be synchronized to have the same
// set of hashes.
targets map[uint64]*Target
loops map[uint64]loop
// Constructor for new scrape loops. This is settable for testing convenience.
newLoop func(context.Context, scraper, func() storage.Appender, func() storage.Appender) loop
}
func newScrapePool(ctx context.Context, cfg *config.ScrapeConfig, app Appendable) *scrapePool {
client, err := NewHTTPClient(cfg.HTTPClientConfig)
if err != nil {
// Any errors that could occur here should be caught during config validation.
log.Errorf("Error creating HTTP client for job %q: %s", cfg.JobName, err)
}
return &scrapePool{
appendable: app,
config: cfg,
ctx: ctx,
client: client,
targets: map[uint64]*Target{},
loops: map[uint64]loop{},
newLoop: newScrapeLoop,
}
}
// stop terminates all scrape loops and returns after they all terminated.
func (sp *scrapePool) stop() {
var wg sync.WaitGroup
sp.mtx.Lock()
defer sp.mtx.Unlock()
for fp, l := range sp.loops {
wg.Add(1)
go func(l loop) {
l.stop()
wg.Done()
}(l)
delete(sp.loops, fp)
delete(sp.targets, fp)
}
wg.Wait()
}
// reload the scrape pool with the given scrape configuration. The target state is preserved
// but all scrape loops are restarted with the new scrape configuration.
// This method returns after all scrape loops that were stopped have fully terminated.
func (sp *scrapePool) reload(cfg *config.ScrapeConfig) {
start := time.Now()
sp.mtx.Lock()
defer sp.mtx.Unlock()
client, err := httputil.NewClientFromConfig(cfg.HTTPClientConfig)
if err != nil {
// Any errors that could occur here should be caught during config validation.
log.Errorf("Error creating HTTP client for job %q: %s", cfg.JobName, err)
}
sp.config = cfg
sp.client = client
var (
wg sync.WaitGroup
interval = time.Duration(sp.config.ScrapeInterval)
timeout = time.Duration(sp.config.ScrapeTimeout)
)
for fp, oldLoop := range sp.loops {
var (
t = sp.targets[fp]
s = &targetScraper{Target: t, client: sp.client, timeout: timeout}
newLoop = sp.newLoop(sp.ctx, s,
func() storage.Appender {
return sp.sampleAppender(t)
},
func() storage.Appender {
return sp.reportAppender(t)
},
)
)
wg.Add(1)
go func(oldLoop, newLoop loop) {
oldLoop.stop()
wg.Done()
go newLoop.run(interval, timeout, nil)
}(oldLoop, newLoop)
sp.loops[fp] = newLoop
}
wg.Wait()
targetReloadIntervalLength.WithLabelValues(interval.String()).Observe(
time.Since(start).Seconds(),
)
}
// Sync converts target groups into actual scrape targets and synchronizes
// the currently running scraper with the resulting set.
func (sp *scrapePool) Sync(tgs []*config.TargetGroup) {
start := time.Now()
var all []*Target
for _, tg := range tgs {
targets, err := targetsFromGroup(tg, sp.config)
if err != nil {
log.With("err", err).Error("creating targets failed")
continue
}
all = append(all, targets...)
}
sp.sync(all)
targetSyncIntervalLength.WithLabelValues(sp.config.JobName).Observe(
time.Since(start).Seconds(),
)
targetScrapePoolSyncsCounter.WithLabelValues(sp.config.JobName).Inc()
}
// sync takes a list of potentially duplicated targets, deduplicates them, starts
// scrape loops for new targets, and stops scrape loops for disappeared targets.
// It returns after all stopped scrape loops terminated.
func (sp *scrapePool) sync(targets []*Target) {
sp.mtx.Lock()
defer sp.mtx.Unlock()
var (
uniqueTargets = map[uint64]struct{}{}
interval = time.Duration(sp.config.ScrapeInterval)
timeout = time.Duration(sp.config.ScrapeTimeout)
)
for _, t := range targets {
t := t
hash := t.hash()
uniqueTargets[hash] = struct{}{}
if _, ok := sp.targets[hash]; !ok {
s := &targetScraper{Target: t, client: sp.client, timeout: timeout}
l := sp.newLoop(sp.ctx, s,
func() storage.Appender {
return sp.sampleAppender(t)
},
func() storage.Appender {
return sp.reportAppender(t)
},
)
sp.targets[hash] = t
sp.loops[hash] = l
go l.run(interval, timeout, nil)
}
}
var wg sync.WaitGroup
// Stop and remove old targets and scraper loops.
for hash := range sp.targets {
if _, ok := uniqueTargets[hash]; !ok {
wg.Add(1)
go func(l loop) {
l.stop()
wg.Done()
}(sp.loops[hash])
delete(sp.loops, hash)
delete(sp.targets, hash)
}
}
// Wait for all potentially stopped scrapers to terminate.
// This covers the case of flapping targets. If the server is under high load, a new scraper
// may be active and tries to insert. The old scraper that didn't terminate yet could still
// be inserting a previous sample set.
wg.Wait()
}
// sampleAppender returns an appender for ingested samples from the target.
func (sp *scrapePool) sampleAppender(target *Target) storage.Appender {
app, err := sp.appendable.Appender()
if err != nil {
panic(err)
}
// The limit is applied after metrics are potentially dropped via relabeling.
if sp.config.SampleLimit > 0 {
app = &limitAppender{
Appender: app,
limit: int(sp.config.SampleLimit),
}
}
// The relabelAppender has to be inside the label-modifying appenders
// so the relabeling rules are applied to the correct label set.
if mrc := sp.config.MetricRelabelConfigs; len(mrc) > 0 {
app = relabelAppender{
Appender: app,
relabelings: mrc,
}
}
if sp.config.HonorLabels {
app = honorLabelsAppender{
Appender: app,
labels: target.Labels(),
}
} else {
app = ruleLabelsAppender{
Appender: app,
labels: target.Labels(),
}
}
return app
}
// reportAppender returns an appender for reporting samples for the target.
func (sp *scrapePool) reportAppender(target *Target) storage.Appender {
app, err := sp.appendable.Appender()
if err != nil {
panic(err)
}
return ruleLabelsAppender{
Appender: app,
labels: target.Labels(),
}
}
// A scraper retrieves samples and accepts a status report at the end.
type scraper interface {
scrape(ctx context.Context, w io.Writer) error
report(start time.Time, dur time.Duration, err error)
offset(interval time.Duration) time.Duration
}
// targetScraper implements the scraper interface for a target.
type targetScraper struct {
*Target
client *http.Client
req *http.Request
timeout time.Duration
gzipr *gzip.Reader
buf *bufio.Reader
}
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,*/*;q=0.1`
var userAgentHeader = fmt.Sprintf("Prometheus/%s", version.Version)
func (s *targetScraper) scrape(ctx context.Context, w io.Writer) error {
if s.req == nil {
req, err := http.NewRequest("GET", s.URL().String(), nil)
if err != nil {
return err
}
// Disable accept header to always negotiate for text format.
// req.Header.Add("Accept", acceptHeader)
req.Header.Add("Accept-Encoding", "gzip")
req.Header.Set("User-Agent", userAgentHeader)
req.Header.Set("X-Prometheus-Scrape-Timeout-Seconds", fmt.Sprintf("%f", s.timeout.Seconds()))
s.req = req
}
resp, err := ctxhttp.Do(ctx, s.client, s.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)
}
if resp.Header.Get("Content-Encoding") != "gzip" {
_, err = io.Copy(w, resp.Body)
return err
}
if s.gzipr == nil {
s.buf = bufio.NewReader(resp.Body)
s.gzipr, err = gzip.NewReader(s.buf)
if err != nil {
return err
}
} else {
s.buf.Reset(resp.Body)
s.gzipr.Reset(s.buf)
}
_, err = io.Copy(w, s.gzipr)
s.gzipr.Close()
return err
}
// A loop can run and be stopped again. It must not be reused after it was stopped.
type loop interface {
run(interval, timeout time.Duration, errc chan<- error)
stop()
}
type scrapeLoop struct {
scraper scraper
appender func() storage.Appender
reportAppender func() storage.Appender
cache map[string]uint64
done chan struct{}
ctx context.Context
cancel func()
}
func newScrapeLoop(ctx context.Context, sc scraper, app, reportApp func() storage.Appender) loop {
sl := &scrapeLoop{
scraper: sc,
appender: app,
reportAppender: reportApp,
cache: map[string]uint64{},
done: make(chan struct{}),
}
sl.ctx, sl.cancel = context.WithCancel(ctx)
return sl
}
func (sl *scrapeLoop) run(interval, timeout time.Duration, errc chan<- error) {
defer close(sl.done)
select {
case <-time.After(sl.scraper.offset(interval)):
// Continue after a scraping offset.
case <-sl.ctx.Done():
return
}
var last time.Time
ticker := time.NewTicker(interval)
defer ticker.Stop()
buf := bytes.NewBuffer(make([]byte, 0, 16000))
for {
buf.Reset()
select {
case <-sl.ctx.Done():
return
default:
}
var (
total, added int
start = time.Now()
scrapeCtx, _ = context.WithTimeout(sl.ctx, timeout)
)
// Only record after the first scrape.
if !last.IsZero() {
targetIntervalLength.WithLabelValues(interval.String()).Observe(
time.Since(last).Seconds(),
)
}
err := sl.scraper.scrape(scrapeCtx, buf)
if err == nil {
b := buf.Bytes()
if total, added, err = sl.append(b, start); err != nil {
log.With("err", err).Error("append failed")
}
} else if errc != nil {
errc <- err
}
sl.report(start, time.Since(start), total, added, err)
last = start
select {
case <-sl.ctx.Done():
return
case <-ticker.C:
}
}
}
func (sl *scrapeLoop) stop() {
sl.cancel()
<-sl.done
}
type sample struct {
metric labels.Labels
t int64
v float64
}
type samples []sample
func (s samples) Len() int { return len(s) }
func (s samples) Swap(i, j int) { s[i], s[j] = s[j], s[i] }
func (s samples) Less(i, j int) bool {
d := labels.Compare(s[i].metric, s[j].metric)
if d < 0 {
return true
} else if d > 0 {
return false
}
return s[i].t < s[j].t
}
func (sl *scrapeLoop) append(b []byte, ts time.Time) (total, added int, err error) {
var (
app = sl.appender()
p = textparse.New(b)
defTime = timestamp.FromTime(ts)
)
loop:
for p.Next() {
total++
t := defTime
met, tp, v := p.At()
if tp != nil {
t = *tp
}
mets := yoloString(met)
ref, ok := sl.cache[mets]
if ok {
switch err = app.AddFast(ref, t, v); err {
case nil:
case storage.ErrNotFound:
ok = false
case errSeriesDropped:
continue
default:
break loop
}
}
if !ok {
var lset labels.Labels
p.Metric(&lset)
ref, err = app.Add(lset, t, v)
// TODO(fabxc): also add a dropped-cache?
switch err {
case nil:
case errSeriesDropped:
continue
default:
break loop
}
// Allocate a real string.
mets = string(met)
sl.cache[mets] = ref
}
added++
}
if err == nil {
err = p.Err()
}
if err != nil {
app.Rollback()
return total, 0, err
}
if err := app.Commit(); err != nil {
return total, 0, err
}
return total, added, nil
}
func yoloString(b []byte) string {
return *((*string)(unsafe.Pointer(&b)))
}
func (sl *scrapeLoop) report(start time.Time, duration time.Duration, scraped, appended int, err error) error {
sl.scraper.report(start, duration, err)
ts := timestamp.FromTime(start)
var health float64
if err == nil {
health = 1
}
app := sl.reportAppender()
if err := sl.addReportSample(app, scrapeHealthMetricName, ts, health); err != nil {
app.Rollback()
return err
}
if err := sl.addReportSample(app, scrapeDurationMetricName, ts, duration.Seconds()); err != nil {
app.Rollback()
return err
}
if err := sl.addReportSample(app, scrapeSamplesMetricName, ts, float64(scraped)); err != nil {
app.Rollback()
return err
}
if err := sl.addReportSample(app, samplesPostRelabelMetricName, ts, float64(appended)); err != nil {
app.Rollback()
return err
}
return app.Commit()
}
func (sl *scrapeLoop) addReportSample(app storage.Appender, s string, t int64, v float64) error {
ref, ok := sl.cache[s]
if ok {
if err := app.AddFast(ref, t, v); err == nil {
return nil
} else if err != storage.ErrNotFound {
return err
}
}
met := labels.Labels{
labels.Label{Name: labels.MetricName, Value: s},
}
ref, err := app.Add(met, t, v)
if err != nil {
return err
}
sl.cache[s] = ref
return nil
}