prometheus/retrieval/target.go

315 lines
9.3 KiB
Go

// Copyright 2013 Prometheus Team
// 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 (
"bytes"
"fmt"
"log"
"net/http"
"os"
"strings"
"time"
"github.com/prometheus/client_golang/extraction"
clientmodel "github.com/prometheus/client_golang/model"
)
const (
InstanceLabel clientmodel.LabelName = "instance"
// The metric name for the synthetic health variable.
ScrapeHealthMetricName clientmodel.LabelValue = "up"
)
var localhostRepresentations = []string{"http://127.0.0.1", "http://localhost"}
// The state of the given 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 (
// The Target has not been seen; we know nothing about it, except that it is
// on our docket for examination.
UNKNOWN TargetState = iota
// The Target has been found and successfully queried.
ALIVE
// The Target was either historically found or not found and then determined
// to be unhealthy by either not responding or disappearing.
UNREACHABLE
)
// A healthReporter is a type that can provide insight into its health state.
//
// It mainly exists for testability reasons to decouple the scheduler behaviors
// from fully-fledged Target and other types.
type healthReporter interface {
// Report the last-known health state for this target.
State() TargetState
}
// 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 {
// Retrieve values from this target.
//
// earliest refers to the soonest available opportunity to reschedule the
// target for a future retrieval. It is up to the underlying scheduler type,
// alluded to in the scheduledFor function, to use this as it wants to. The
// current use case is to create a common batching time for scraping multiple
// Targets in the future through the TargetPool.
Scrape(earliest time.Time, results chan<- *extraction.Result) error
// Fulfill the healthReporter interface.
State() TargetState
// Report the soonest time at which this Target may be scheduled for
// retrieval. This value needn't convey that the operation occurs at this
// time, but it should occur no sooner than it.
//
// Right now, this is used as the sorting key in TargetPool.
ScheduledFor() time.Time
// EstimatedTimeToExecute emits the amount of time until the next prospective
// scheduling opportunity for this target.
EstimatedTimeToExecute() time.Duration
// Return the last encountered scrape error, if any.
LastError() error
// The address 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.
Address() string
// The address as seen from other hosts. References to localhost are resolved
// to the address of the prometheus server.
GlobalAddress() string
// Return the target's base labels.
BaseLabels() clientmodel.LabelSet
// Merge a new externally supplied target definition (e.g. with changed base
// labels) into an old target definition for the same endpoint. Preserve
// remaining information - like health state - from the old target.
Merge(newTarget Target)
}
// target is a Target that refers to a singular HTTP or HTTPS endpoint.
type target struct {
// scheduler provides the scheduling strategy that is used to formulate what
// is returned in Target.scheduledFor.
scheduler scheduler
// The current health state of the target.
state TargetState
// The last encountered scrape error, if any.
lastError error
address 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.
client http.Client
}
// Furnish a reasonably configured target for querying.
func NewTarget(address string, deadline time.Duration, baseLabels clientmodel.LabelSet) Target {
target := &target{
address: address,
Deadline: deadline,
baseLabels: baseLabels,
client: NewDeadlineClient(deadline),
}
scheduler := &healthScheduler{
target: target,
}
target.scheduler = scheduler
return target
}
func (t *target) recordScrapeHealth(results chan<- *extraction.Result, timestamp time.Time, healthy bool) {
metric := clientmodel.Metric{}
for label, value := range t.baseLabels {
metric[label] = value
}
metric[clientmodel.MetricNameLabel] = clientmodel.LabelValue(ScrapeHealthMetricName)
metric[InstanceLabel] = clientmodel.LabelValue(t.Address())
healthValue := clientmodel.SampleValue(0)
if healthy {
healthValue = clientmodel.SampleValue(1)
}
sample := &clientmodel.Sample{
Metric: metric,
Timestamp: timestamp,
Value: healthValue,
}
results <- &extraction.Result{
Err: nil,
Samples: clientmodel.Samples{sample},
}
}
func (t *target) Scrape(earliest time.Time, results chan<- *extraction.Result) error {
now := time.Now()
futureState := t.state
err := t.scrape(now, results)
if err != nil {
t.recordScrapeHealth(results, now, false)
futureState = UNREACHABLE
} else {
t.recordScrapeHealth(results, now, true)
futureState = ALIVE
}
t.scheduler.Reschedule(earliest, futureState)
t.state = futureState
t.lastError = err
return err
}
const acceptHeader = `application/vnd.google.protobuf;proto=io.prometheus.client.MetricFamily;encoding=delimited;q=0.7,application/json;schema=prometheus/telemetry;version=0.0.2;q=0.2,*/*;q=0.1`
func (t *target) scrape(timestamp time.Time, results chan<- *extraction.Result) (err error) {
defer func(start time.Time) {
ms := float64(time.Since(start)) / float64(time.Millisecond)
labels := map[string]string{address: t.Address(), outcome: success}
if err != nil {
labels[outcome] = failure
}
targetOperationLatencies.Add(labels, ms)
targetOperations.Increment(labels)
}(time.Now())
req, err := http.NewRequest("GET", t.Address(), nil)
if err != nil {
panic(err)
}
req.Header.Add("Accept", acceptHeader)
resp, err := t.client.Do(req)
if err != nil {
return err
}
defer resp.Body.Close()
processor, err := extraction.ProcessorForRequestHeader(resp.Header)
if err != nil {
return err
}
// XXX: This is a wart; we need to handle this more gracefully down the
// road, especially once we have service discovery support.
baseLabels := clientmodel.LabelSet{InstanceLabel: clientmodel.LabelValue(t.Address())}
for baseLabel, baseValue := range t.baseLabels {
baseLabels[baseLabel] = baseValue
}
processOptions := &extraction.ProcessOptions{
Timestamp: timestamp,
BaseLabels: baseLabels,
}
// N.B. - It is explicitly required to extract the entire payload before
// attempting to deserialize, as the underlying reader expects will
// interpret pending data as a truncated message.
buf := new(bytes.Buffer)
if _, err := buf.ReadFrom(resp.Body); err != nil {
return err
}
return processor.ProcessSingle(buf, results, processOptions)
}
func (t *target) State() TargetState {
return t.state
}
func (t *target) ScheduledFor() time.Time {
return t.scheduler.ScheduledFor()
}
func (t *target) EstimatedTimeToExecute() time.Duration {
return t.scheduler.ScheduledFor().Sub(time.Now())
}
func (t *target) LastError() error {
return t.lastError
}
func (t *target) Address() string {
return t.address
}
func (t *target) GlobalAddress() string {
address := t.address
hostname, err := os.Hostname()
if err != nil {
log.Printf("Couldn't get hostname: %s, returning target.Address()", err)
return address
}
for _, localhostRepresentation := range localhostRepresentations {
address = strings.Replace(address, localhostRepresentation, fmt.Sprintf("http://%s", hostname), -1)
}
return address
}
func (t *target) BaseLabels() clientmodel.LabelSet {
return t.baseLabels
}
// Merge a new externally supplied target definition (e.g. with changed base
// labels) into an old target definition for the same endpoint. Preserve
// remaining information - like health state - from the old target.
func (t *target) Merge(newTarget Target) {
if t.Address() != newTarget.Address() {
panic("targets don't refer to the same endpoint")
}
t.baseLabels = newTarget.BaseLabels()
}
type targets []Target
func (t targets) Len() int {
return len(t)
}
func (t targets) Less(i, j int) bool {
return t[i].ScheduledFor().Before(t[j].ScheduledFor())
}
func (t targets) Swap(i, j int) {
t[i], t[j] = t[j], t[i]
}