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notifier.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 notifier
import (
"bytes"
"encoding/json"
"fmt"
"net"
"net/http"
"net/url"
"path"
"strings"
"sync"
"sync/atomic"
"time"
"github.com/prometheus/client_golang/prometheus"
"github.com/prometheus/common/log"
"github.com/prometheus/common/model"
"golang.org/x/net/context"
"golang.org/x/net/context/ctxhttp"
"github.com/prometheus/prometheus/config"
"github.com/prometheus/prometheus/discovery"
"github.com/prometheus/prometheus/relabel"
"github.com/prometheus/prometheus/util/httputil"
)
const (
alertPushEndpoint = "/api/v1/alerts"
contentTypeJSON = "application/json"
)
// String constants for instrumentation.
const (
namespace = "prometheus"
subsystem = "notifications"
alertmanagerLabel = "alertmanager"
)
// Notifier is responsible for dispatching alert notifications to an
// alert manager service.
type Notifier struct {
queue model.Alerts
opts *Options
metrics *alertMetrics
more chan struct{}
mtx sync.RWMutex
ctx context.Context
cancel func()
alertmanagers []*alertmanagerSet
cancelDiscovery func()
logger log.Logger
}
// Options are the configurable parameters of a Handler.
type Options struct {
QueueCapacity int
ExternalLabels model.LabelSet
RelabelConfigs []*config.RelabelConfig
// Used for sending HTTP requests to the Alertmanager.
Do func(ctx context.Context, client *http.Client, req *http.Request) (*http.Response, error)
Registerer prometheus.Registerer
}
type alertMetrics struct {
latency *prometheus.SummaryVec
errors *prometheus.CounterVec
sent *prometheus.CounterVec
dropped prometheus.Counter
queueLength prometheus.GaugeFunc
queueCapacity prometheus.Gauge
alertmanagersDiscovered prometheus.GaugeFunc
}
func newAlertMetrics(r prometheus.Registerer, queueCap int, queueLen, alertmanagersDiscovered func() float64) *alertMetrics {
m := &alertMetrics{
latency: prometheus.NewSummaryVec(prometheus.SummaryOpts{
Namespace: namespace,
Subsystem: subsystem,
Name: "latency_seconds",
Help: "Latency quantiles for sending alert notifications (not including dropped notifications).",
},
[]string{alertmanagerLabel},
),
errors: prometheus.NewCounterVec(prometheus.CounterOpts{
Namespace: namespace,
Subsystem: subsystem,
Name: "errors_total",
Help: "Total number of errors sending alert notifications.",
},
[]string{alertmanagerLabel},
),
sent: prometheus.NewCounterVec(prometheus.CounterOpts{
Namespace: namespace,
Subsystem: subsystem,
Name: "sent_total",
Help: "Total number of alerts successfully sent.",
},
[]string{alertmanagerLabel},
),
dropped: prometheus.NewCounter(prometheus.CounterOpts{
Namespace: namespace,
Subsystem: subsystem,
Name: "dropped_total",
Help: "Total number of alerts dropped due to errors when sending to Alertmanager.",
}),
queueLength: prometheus.NewGaugeFunc(prometheus.GaugeOpts{
Namespace: namespace,
Subsystem: subsystem,
Name: "queue_length",
Help: "The number of alert notifications in the queue.",
}, queueLen),
queueCapacity: prometheus.NewGauge(prometheus.GaugeOpts{
Namespace: namespace,
Subsystem: subsystem,
Name: "queue_capacity",
Help: "The capacity of the alert notifications queue.",
}),
alertmanagersDiscovered: prometheus.NewGaugeFunc(prometheus.GaugeOpts{
Name: "prometheus_notifications_alertmanagers_discovered",
Help: "The number of alertmanagers discovered and active.",
}, alertmanagersDiscovered),
}
m.queueCapacity.Set(float64(queueCap))
if r != nil {
r.MustRegister(
m.latency,
m.errors,
m.sent,
m.dropped,
m.queueLength,
m.queueCapacity,
m.alertmanagersDiscovered,
)
}
return m
}
// New constructs a new Notifier.
func New(o *Options, logger log.Logger) *Notifier {
ctx, cancel := context.WithCancel(context.Background())
if o.Do == nil {
o.Do = ctxhttp.Do
}
n := &Notifier{
queue: make(model.Alerts, 0, o.QueueCapacity),
ctx: ctx,
cancel: cancel,
more: make(chan struct{}, 1),
opts: o,
logger: logger,
}
queueLenFunc := func() float64 { return float64(n.queueLen()) }
alertmanagersDiscoveredFunc := func() float64 { return float64(len(n.Alertmanagers())) }
n.metrics = newAlertMetrics(o.Registerer, o.QueueCapacity, queueLenFunc, alertmanagersDiscoveredFunc)
return n
}
// ApplyConfig updates the status state as the new config requires.
func (n *Notifier) ApplyConfig(conf *config.Config) error {
n.mtx.Lock()
defer n.mtx.Unlock()
n.opts.ExternalLabels = conf.GlobalConfig.ExternalLabels
n.opts.RelabelConfigs = conf.AlertingConfig.AlertRelabelConfigs
amSets := []*alertmanagerSet{}
ctx, cancel := context.WithCancel(n.ctx)
for _, cfg := range conf.AlertingConfig.AlertmanagerConfigs {
ams, err := newAlertmanagerSet(cfg, n.logger)
if err != nil {
return err
}
ams.metrics = n.metrics
amSets = append(amSets, ams)
}
// After all sets were created successfully, start them and cancel the
// old ones.
for _, ams := range amSets {
go ams.ts.Run(ctx)
ams.ts.UpdateProviders(discovery.ProvidersFromConfig(ams.cfg.ServiceDiscoveryConfig, n.logger))
}
if n.cancelDiscovery != nil {
n.cancelDiscovery()
}
n.cancelDiscovery = cancel
n.alertmanagers = amSets
return nil
}
const maxBatchSize = 64
func (n *Notifier) queueLen() int {
n.mtx.RLock()
defer n.mtx.RUnlock()
return len(n.queue)
}
func (n *Notifier) nextBatch() []*model.Alert {
n.mtx.Lock()
defer n.mtx.Unlock()
var alerts model.Alerts
if len(n.queue) > maxBatchSize {
alerts = append(make(model.Alerts, 0, maxBatchSize), n.queue[:maxBatchSize]...)
n.queue = n.queue[maxBatchSize:]
} else {
alerts = append(make(model.Alerts, 0, len(n.queue)), n.queue...)
n.queue = n.queue[:0]
}
return alerts
}
// Run dispatches notifications continuously.
func (n *Notifier) Run() {
for {
select {
case <-n.ctx.Done():
return
case <-n.more:
}
alerts := n.nextBatch()
if !n.sendAll(alerts...) {
n.metrics.dropped.Add(float64(len(alerts)))
}
// If the queue still has items left, kick off the next iteration.
if n.queueLen() > 0 {
n.setMore()
}
}
}
// Send queues the given notification requests for processing.
// Panics if called on a handler that is not running.
func (n *Notifier) Send(alerts ...*model.Alert) {
n.mtx.Lock()
defer n.mtx.Unlock()
// Attach external labels before relabelling and sending.
for _, a := range alerts {
for ln, lv := range n.opts.ExternalLabels {
if _, ok := a.Labels[ln]; !ok {
a.Labels[ln] = lv
}
}
}
alerts = n.relabelAlerts(alerts)
// Queue capacity should be significantly larger than a single alert
// batch could be.
if d := len(alerts) - n.opts.QueueCapacity; d > 0 {
alerts = alerts[d:]
n.logger.Warnf("Alert batch larger than queue capacity, dropping %d alerts", d)
n.metrics.dropped.Add(float64(d))
}
// If the queue is full, remove the oldest alerts in favor
// of newer ones.
if d := (len(n.queue) + len(alerts)) - n.opts.QueueCapacity; d > 0 {
n.queue = n.queue[d:]
n.logger.Warnf("Alert notification queue full, dropping %d alerts", d)
n.metrics.dropped.Add(float64(d))
}
n.queue = append(n.queue, alerts...)
// Notify sending goroutine that there are alerts to be processed.
n.setMore()
}
func (n *Notifier) relabelAlerts(alerts []*model.Alert) []*model.Alert {
var relabeledAlerts []*model.Alert
for _, alert := range alerts {
labels := relabel.Process(alert.Labels, n.opts.RelabelConfigs...)
if labels != nil {
alert.Labels = labels
relabeledAlerts = append(relabeledAlerts, alert)
}
}
return relabeledAlerts
}
// setMore signals that the alert queue has items.
func (n *Notifier) setMore() {
// If we cannot send on the channel, it means the signal already exists
// and has not been consumed yet.
select {
case n.more <- struct{}{}:
default:
}
}
// Alertmanagers returns a slice of Alertmanager URLs.
func (n *Notifier) Alertmanagers() []*url.URL {
n.mtx.RLock()
amSets := n.alertmanagers
n.mtx.RUnlock()
var res []*url.URL
for _, ams := range amSets {
ams.mtx.RLock()
for _, am := range ams.ams {
res = append(res, am.url())
}
ams.mtx.RUnlock()
}
return res
}
// sendAll sends the alerts to all configured Alertmanagers concurrently.
// It returns true if the alerts could be sent successfully to at least one Alertmanager.
func (n *Notifier) sendAll(alerts ...*model.Alert) bool {
begin := time.Now()
b, err := json.Marshal(alerts)
if err != nil {
n.logger.Errorf("Encoding alerts failed: %s", err)
return false
}
n.mtx.RLock()
amSets := n.alertmanagers
n.mtx.RUnlock()
var (
wg sync.WaitGroup
numSuccess uint64
)
for _, ams := range amSets {
ams.mtx.RLock()
for _, am := range ams.ams {
wg.Add(1)
ctx, cancel := context.WithTimeout(n.ctx, ams.cfg.Timeout)
defer cancel()
go func(am alertmanager) {
u := am.url().String()
if err := n.sendOne(ctx, ams.client, u, b); err != nil {
n.logger.With("alertmanager", u).With("count", len(alerts)).Errorf("Error sending alerts: %s", err)
n.metrics.errors.WithLabelValues(u).Inc()
} else {
atomic.AddUint64(&numSuccess, 1)
}
n.metrics.latency.WithLabelValues(u).Observe(time.Since(begin).Seconds())
n.metrics.sent.WithLabelValues(u).Add(float64(len(alerts)))
wg.Done()
}(am)
}
ams.mtx.RUnlock()
}
wg.Wait()
return numSuccess > 0
}
func (n *Notifier) sendOne(ctx context.Context, c *http.Client, url string, b []byte) error {
req, err := http.NewRequest("POST", url, bytes.NewReader(b))
if err != nil {
return err
}
req.Header.Set("Content-Type", contentTypeJSON)
resp, err := n.opts.Do(ctx, c, req)
if err != nil {
return err
}
defer resp.Body.Close()
// Any HTTP status 2xx is OK.
if resp.StatusCode/100 != 2 {
return fmt.Errorf("bad response status %v", resp.Status)
}
return err
}
// Stop shuts down the notification handler.
func (n *Notifier) Stop() {
n.logger.Info("Stopping notification handler...")
n.cancel()
}
// alertmanager holds Alertmanager endpoint information.
type alertmanager interface {
url() *url.URL
}
type alertmanagerLabels model.LabelSet
const pathLabel = "__alerts_path__"
func (a alertmanagerLabels) url() *url.URL {
return &url.URL{
Scheme: string(a[model.SchemeLabel]),
Host: string(a[model.AddressLabel]),
Path: string(a[pathLabel]),
}
}
// alertmanagerSet contains a set of Alertmanagers discovered via a group of service
// discovery definitions that have a common configuration on how alerts should be sent.
type alertmanagerSet struct {
ts *discovery.TargetSet
cfg *config.AlertmanagerConfig
client *http.Client
metrics *alertMetrics
mtx sync.RWMutex
ams []alertmanager
logger log.Logger
}
func newAlertmanagerSet(cfg *config.AlertmanagerConfig, logger log.Logger) (*alertmanagerSet, error) {
client, err := httputil.NewClientFromConfig(cfg.HTTPClientConfig)
if err != nil {
return nil, err
}
s := &alertmanagerSet{
client: client,
cfg: cfg,
logger: logger,
}
s.ts = discovery.NewTargetSet(s)
return s, nil
}
// Sync extracts a deduplicated set of Alertmanager endpoints from a list
// of target groups definitions.
func (s *alertmanagerSet) Sync(tgs []*config.TargetGroup) {
all := []alertmanager{}
for _, tg := range tgs {
ams, err := alertmanagerFromGroup(tg, s.cfg)
if err != nil {
s.logger.With("err", err).Error("generating discovered Alertmanagers failed")
continue
}
all = append(all, ams...)
}
s.mtx.Lock()
defer s.mtx.Unlock()
// Set new Alertmanagers and deduplicate them along their unique URL.
s.ams = []alertmanager{}
seen := map[string]struct{}{}
for _, am := range all {
us := am.url().String()
if _, ok := seen[us]; ok {
continue
}
// This will initialise the Counters for the AM to 0.
s.metrics.sent.WithLabelValues(us)
s.metrics.errors.WithLabelValues(us)
seen[us] = struct{}{}
s.ams = append(s.ams, am)
}
}
func postPath(pre string) string {
return path.Join("/", pre, alertPushEndpoint)
}
// alertmanagersFromGroup extracts a list of alertmanagers from a target group and an associcated
// AlertmanagerConfig.
func alertmanagerFromGroup(tg *config.TargetGroup, cfg *config.AlertmanagerConfig) ([]alertmanager, error) {
var res []alertmanager
for _, lset := range tg.Targets {
lset = lset.Clone()
// Set configured scheme as the initial scheme label for overwrite.
lset[model.SchemeLabel] = model.LabelValue(cfg.Scheme)
lset[pathLabel] = model.LabelValue(postPath(cfg.PathPrefix))
// Combine target labels with target group labels.
for ln, lv := range tg.Labels {
if _, ok := lset[ln]; !ok {
lset[ln] = lv
}
}
lset = relabel.Process(lset, cfg.RelabelConfigs...)
if lset == nil {
continue
}
// addPort checks whether we should add a default port to the address.
// If the address is not valid, we don't append a port either.
addPort := func(s string) bool {
// If we can split, a port exists and we don't have to add one.
if _, _, err := net.SplitHostPort(s); err == nil {
return false
}
// If adding a port makes it valid, the previous error
// was not due to an invalid address and we can append a port.
_, _, err := net.SplitHostPort(s + ":1234")
return err == nil
}
// If it's an address with no trailing port, infer it based on the used scheme.
if addr := string(lset[model.AddressLabel]); addPort(addr) {
// Addresses reaching this point are already wrapped in [] if necessary.
switch lset[model.SchemeLabel] {
case "http", "":
addr = addr + ":80"
case "https":
addr = addr + ":443"
default:
return nil, fmt.Errorf("invalid scheme: %q", cfg.Scheme)
}
lset[model.AddressLabel] = model.LabelValue(addr)
}
if err := config.CheckTargetAddress(lset[model.AddressLabel]); err != nil {
return nil, err
}
// Meta labels are deleted after relabelling. Other internal labels propagate to
// the target which decides whether they will be part of their label set.
for ln := range lset {
if strings.HasPrefix(string(ln), model.MetaLabelPrefix) {
delete(lset, ln)
}
}
res = append(res, alertmanagerLabels(lset))
}
return res, nil
}