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service_discovery.go
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service_discovery.go
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// SPDX-License-Identifier: AGPL-3.0-only
package ruler
import (
"context"
"fmt"
"net/url"
"time"
"github.com/grafana/dskit/cache"
"github.com/grafana/dskit/dns"
"github.com/pkg/errors"
"github.com/prometheus/client_golang/prometheus"
"github.com/prometheus/common/model"
"github.com/prometheus/prometheus/discovery"
"github.com/prometheus/prometheus/discovery/refresh"
"github.com/prometheus/prometheus/discovery/targetgroup"
)
const (
mechanismName = "dns_sd"
)
type dnsServiceDiscovery struct {
refreshMetrics discovery.RefreshMetricsInstantiator
Resolver cache.AddressProvider
RefreshInterval time.Duration
QType dns.QType
Host string
}
func (dnsServiceDiscovery) Name() string {
return mechanismName
}
func (c dnsServiceDiscovery) NewDiscoverer(opts discovery.DiscovererOptions) (discovery.Discoverer, error) {
return refresh.NewDiscovery(refresh.Options{
Logger: opts.Logger,
Mech: mechanismName,
Interval: c.RefreshInterval,
RefreshF: c.resolve,
MetricsInstantiator: c.refreshMetrics,
}), nil
}
func (c dnsServiceDiscovery) NewDiscovererMetrics(prometheus.Registerer, discovery.RefreshMetricsInstantiator) discovery.DiscovererMetrics {
return &discovery.NoopDiscovererMetrics{}
}
func (c dnsServiceDiscovery) resolve(ctx context.Context) ([]*targetgroup.Group, error) {
if err := c.Resolver.Resolve(ctx, []string{string(c.QType) + "+" + c.Host}); err != nil {
return nil, err
}
resolved := c.Resolver.Addresses()
targets := make([]model.LabelSet, len(resolved))
for i, r := range resolved {
targets[i] = model.LabelSet{
model.AddressLabel: model.LabelValue(r),
}
}
tg := &targetgroup.Group{
Targets: targets,
Source: c.Host,
}
return []*targetgroup.Group{tg}, nil
}
func dnsSD(rulerConfig *Config, resolver cache.AddressProvider, qType dns.QType, url *url.URL, rmi discovery.RefreshMetricsInstantiator) discovery.Config {
return dnsServiceDiscovery{
Resolver: resolver,
RefreshInterval: rulerConfig.AlertmanagerRefreshInterval,
Host: url.Host,
QType: qType,
refreshMetrics: rmi,
}
}
func staticTarget(url *url.URL) discovery.Config {
return discovery.StaticConfig{
{
Targets: []model.LabelSet{{model.AddressLabel: model.LabelValue(url.Host)}},
},
}
}
func sanitizedAlertmanagerURL(amURL string) (isServiceDiscovery bool, qType dns.QType, parsedURL *url.URL, err error) {
rawQType, rawURL := dns.GetQTypeName(amURL)
qType = dns.QType(rawQType)
switch qType {
case "", dns.A, dns.SRV, dns.SRVNoA:
default:
err = errors.Errorf("invalid DNS service discovery prefix %q", qType)
return
}
parsedURL, err = url.Parse(rawURL)
if err != nil {
return
}
if parsedURL.String() == "" || parsedURL.Host == "" {
err = fmt.Errorf("improperly formatted alertmanager URL %q (maybe the scheme is missing?); see DNS Service Discovery docs", rawURL)
return
}
isServiceDiscovery = qType != ""
return
}