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marathon.go
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marathon.go
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// 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 marathon
import (
"encoding/json"
"fmt"
"io/ioutil"
"math/rand"
"net"
"net/http"
"time"
"golang.org/x/net/context"
"github.com/prometheus/client_golang/prometheus"
"github.com/prometheus/common/log"
"github.com/prometheus/common/model"
"github.com/prometheus/prometheus/config"
"github.com/prometheus/prometheus/util/httputil"
)
const (
// metaLabelPrefix is the meta prefix used for all meta labels in this discovery.
metaLabelPrefix = model.MetaLabelPrefix + "marathon_"
// appLabelPrefix is the prefix for the application labels.
appLabelPrefix = metaLabelPrefix + "app_label_"
// appLabel is used for the name of the app in Marathon.
appLabel model.LabelName = metaLabelPrefix + "app"
// imageLabel is the label that is used for the docker image running the service.
imageLabel model.LabelName = metaLabelPrefix + "image"
// taskLabel contains the mesos task name of the app instance.
taskLabel model.LabelName = metaLabelPrefix + "task"
// Constants for instrumentation.
namespace = "prometheus"
)
var (
refreshFailuresCount = prometheus.NewCounter(
prometheus.CounterOpts{
Namespace: namespace,
Name: "sd_marathon_refresh_failures_total",
Help: "The number of Marathon-SD refresh failures.",
})
refreshDuration = prometheus.NewSummary(
prometheus.SummaryOpts{
Namespace: namespace,
Name: "sd_marathon_refresh_duration_seconds",
Help: "The duration of a Marathon-SD refresh in seconds.",
})
)
func init() {
prometheus.MustRegister(refreshFailuresCount)
prometheus.MustRegister(refreshDuration)
}
const appListPath string = "/v2/apps/?embed=apps.tasks"
// Discovery provides service discovery based on a Marathon instance.
type Discovery struct {
client *http.Client
servers []string
refreshInterval time.Duration
lastRefresh map[string]*config.TargetGroup
appsClient AppListClient
}
// Initialize sets up the discovery for usage.
func NewDiscovery(conf *config.MarathonSDConfig) (*Discovery, error) {
tls, err := httputil.NewTLSConfig(conf.TLSConfig)
if err != nil {
return nil, err
}
client := &http.Client{
Timeout: time.Duration(conf.Timeout),
Transport: &http.Transport{
TLSClientConfig: tls,
},
}
return &Discovery{
client: client,
servers: conf.Servers,
refreshInterval: time.Duration(conf.RefreshInterval),
appsClient: fetchApps,
}, nil
}
// Run implements the TargetProvider interface.
func (md *Discovery) Run(ctx context.Context, ch chan<- []*config.TargetGroup) {
for {
select {
case <-ctx.Done():
return
case <-time.After(md.refreshInterval):
err := md.updateServices(ctx, ch)
if err != nil {
log.Errorf("Error while updating services: %s", err)
}
}
}
}
func (md *Discovery) updateServices(ctx context.Context, ch chan<- []*config.TargetGroup) (err error) {
t0 := time.Now()
defer func() {
refreshDuration.Observe(time.Since(t0).Seconds())
if err != nil {
refreshFailuresCount.Inc()
}
}()
targetMap, err := md.fetchTargetGroups()
if err != nil {
return err
}
all := make([]*config.TargetGroup, 0, len(targetMap))
for _, tg := range targetMap {
all = append(all, tg)
}
select {
case <-ctx.Done():
return ctx.Err()
case ch <- all:
}
// Remove services which did disappear.
for source := range md.lastRefresh {
_, ok := targetMap[source]
if !ok {
select {
case <-ctx.Done():
return ctx.Err()
case ch <- []*config.TargetGroup{{Source: source}}:
log.Debugf("Removing group for %s", source)
}
}
}
md.lastRefresh = targetMap
return nil
}
func (md *Discovery) fetchTargetGroups() (map[string]*config.TargetGroup, error) {
url := RandomAppsURL(md.servers)
apps, err := md.appsClient(md.client, url)
if err != nil {
return nil, err
}
groups := AppsToTargetGroups(apps)
return groups, nil
}
// Task describes one instance of a service running on Marathon.
type Task struct {
ID string `json:"id"`
Host string `json:"host"`
Ports []uint32 `json:"ports"`
}
// DockerContainer describes a container which uses the docker runtime.
type DockerContainer struct {
Image string `json:"image"`
}
// Container describes the runtime an app in running in.
type Container struct {
Docker DockerContainer `json:"docker"`
}
// App describes a service running on Marathon.
type App struct {
ID string `json:"id"`
Tasks []Task `json:"tasks"`
RunningTasks int `json:"tasksRunning"`
Labels map[string]string `json:"labels"`
Container Container `json:"container"`
}
// AppList is a list of Marathon apps.
type AppList struct {
Apps []App `json:"apps"`
}
// AppListClient defines a function that can be used to get an application list from marathon.
type AppListClient func(client *http.Client, url string) (*AppList, error)
// fetchApps requests a list of applications from a marathon server.
func fetchApps(client *http.Client, url string) (*AppList, error) {
resp, err := client.Get(url)
if err != nil {
return nil, err
}
body, err := ioutil.ReadAll(resp.Body)
if err != nil {
return nil, err
}
return parseAppJSON(body)
}
func parseAppJSON(body []byte) (*AppList, error) {
apps := &AppList{}
err := json.Unmarshal(body, apps)
if err != nil {
return nil, err
}
return apps, nil
}
// RandomAppsURL randomly selects a server from an array and creates
// an URL pointing to the app list.
func RandomAppsURL(servers []string) string {
// TODO: If possible update server list from Marathon at some point.
server := servers[rand.Intn(len(servers))]
return fmt.Sprintf("%s%s", server, appListPath)
}
// AppsToTargetGroups takes an array of Marathon apps and converts them into target groups.
func AppsToTargetGroups(apps *AppList) map[string]*config.TargetGroup {
tgroups := map[string]*config.TargetGroup{}
for _, a := range apps.Apps {
group := createTargetGroup(&a)
tgroups[group.Source] = group
}
return tgroups
}
func createTargetGroup(app *App) *config.TargetGroup {
var (
targets = targetsForApp(app)
appName = model.LabelValue(app.ID)
image = model.LabelValue(app.Container.Docker.Image)
)
tg := &config.TargetGroup{
Targets: targets,
Labels: model.LabelSet{
appLabel: appName,
imageLabel: image,
},
Source: app.ID,
}
for ln, lv := range app.Labels {
ln = appLabelPrefix + ln
tg.Labels[model.LabelName(ln)] = model.LabelValue(lv)
}
return tg
}
func targetsForApp(app *App) []model.LabelSet {
targets := make([]model.LabelSet, 0, len(app.Tasks))
for _, t := range app.Tasks {
if len(t.Ports) == 0 {
continue
}
target := targetForTask(&t)
targets = append(targets, model.LabelSet{
model.AddressLabel: model.LabelValue(target),
taskLabel: model.LabelValue(t.ID),
})
}
return targets
}
func targetForTask(task *Task) string {
return net.JoinHostPort(task.Host, fmt.Sprintf("%d", task.Ports[0]))
}