prometheus/discovery/discovery.go

118 lines
3.7 KiB
Go

// Copyright 2020 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 discovery
import (
"context"
"reflect"
"github.com/go-kit/log"
"github.com/prometheus/common/config"
"github.com/prometheus/prometheus/discovery/targetgroup"
)
// Discoverer provides information about target groups. It maintains a set
// of sources from which TargetGroups can originate. Whenever a discovery provider
// detects a potential change, it sends the TargetGroup through its channel.
//
// Discoverer does not know if an actual change happened.
// It does guarantee that it sends the new TargetGroup whenever a change happens.
//
// Discoverers should initially send a full set of all discoverable TargetGroups.
type Discoverer interface {
// Run hands a channel to the discovery provider (Consul, DNS, etc.) through which
// it can send updated target groups. It must return when the context is canceled.
// It should not close the update channel on returning.
Run(ctx context.Context, up chan<- []*targetgroup.Group)
}
// DiscovererOptions provides options for a Discoverer.
type DiscovererOptions struct {
Logger log.Logger
}
// A Config provides the configuration and constructor for a Discoverer.
type Config interface {
// Name returns the name of the discovery mechanism.
Name() string
// NewDiscoverer returns a Discoverer for the Config
// with the given DiscovererOptions.
NewDiscoverer(DiscovererOptions) (Discoverer, error)
}
// Configs is a slice of Config values that uses custom YAML marshaling and unmarshaling
// to represent itself as a mapping of the Config values grouped by their types.
type Configs []Config
// SetDirectory joins any relative file paths with dir.
func (c *Configs) SetDirectory(dir string) {
for _, c := range *c {
if v, ok := c.(config.DirectorySetter); ok {
v.SetDirectory(dir)
}
}
}
// UnmarshalYAML implements yaml.Unmarshaler.
func (c *Configs) UnmarshalYAML(unmarshal func(interface{}) error) error {
cfgTyp := getConfigType(configsType)
cfgPtr := reflect.New(cfgTyp)
cfgVal := cfgPtr.Elem()
if err := unmarshal(cfgPtr.Interface()); err != nil {
return replaceYAMLTypeError(err, cfgTyp, configsType)
}
var err error
*c, err = readConfigs(cfgVal, 0)
return err
}
// MarshalYAML implements yaml.Marshaler.
func (c Configs) MarshalYAML() (interface{}, error) {
cfgTyp := getConfigType(configsType)
cfgPtr := reflect.New(cfgTyp)
cfgVal := cfgPtr.Elem()
if err := writeConfigs(cfgVal, c); err != nil {
return nil, err
}
return cfgPtr.Interface(), nil
}
// A StaticConfig is a Config that provides a static list of targets.
type StaticConfig []*targetgroup.Group
// Name returns the name of the service discovery mechanism.
func (StaticConfig) Name() string { return "static" }
// NewDiscoverer returns a Discoverer for the Config.
func (c StaticConfig) NewDiscoverer(DiscovererOptions) (Discoverer, error) {
return staticDiscoverer(c), nil
}
type staticDiscoverer []*targetgroup.Group
func (c staticDiscoverer) Run(ctx context.Context, up chan<- []*targetgroup.Group) {
// TODO: existing implementation closes up chan, but documentation explicitly forbids it...?
defer close(up)
select {
case <-ctx.Done():
case up <- c:
}
}