Attach task and service meta labels to targets

This adds some SD meta labels to discovered targets:

- the Docker task name
- the task's desired state (currently we only select running tasks)
- Docker service labels
- Docker task labels

These meta labels can be used in Prometheus's SD relabeling phase to
keep/drop/update/labelmap/... targets.

See for example how Kubernetes SD does this:

https://prometheus.io/docs/operating/configuration/#pod

There is probably more metadata that should be added in the future.

Dockerfile

@@ -9,4 +9,4 @@ RUN cd /go/src/github.com/weaveworks/prometheus-swarm/ && glide install
 
 RUN CGO_ENABLED=0 GOOS=linux go build -a -installsuffix cgo -o /app/main /go/src/github.com/weaveworks/prometheus-swarm/swarm.go
 
-ENTRYPOINT ["/app/main", "discover"]
+ENTRYPOINT ["/app/main", "discover"]

swarm.go

@@ -16,6 +16,8 @@ import (
  "github.com/docker/docker/api/types/network"
  "github.com/docker/docker/api/types/swarm"
  "github.com/docker/docker/client"
+ "github.com/prometheus/common/model"
+ "github.com/prometheus/prometheus/util/strutil"
  "github.com/spf13/cobra"
 )
 
@@ -211,6 +213,23 @@ func collectIPs(task swarm.Task) ([]net.IP, map[string]swarm.Network) {
  return containerIPs, taskNetworks
 }
 
+func taskLabels(task swarm.Task, serviceIDMap map[string]swarm.Service) map[string]string {
+ service := serviceIDMap[task.ServiceID]
+ labels := map[string]string{
+ model.JobLabel: service.Spec.Name,
+
+ model.MetaLabelPrefix + "docker_task_name": task.Name,
+ model.MetaLabelPrefix + "docker_task_desired_state": string(task.DesiredState),
+ }
+ for k, v := range task.Labels {
+ labels[strutil.SanitizeLabelName(model.MetaLabelPrefix+"docker_task_label_"+k)] = v
+ }
+ for k, v := range service.Spec.Labels {
+ labels[strutil.SanitizeLabelName(model.MetaLabelPrefix+"docker_service_label_"+k)] = v
+ }
+ return labels
+}
+
 func discoverSwarm(prometheusContainerID string, outputFile string, discoveryType string) {
  cli, err := client.NewEnvClient()
  if err != nil {
@@ -275,12 +294,10 @@ func discoverSwarm(prometheusContainerID string, outputFile string, discoveryTyp
 
  scrapetask := scrapeTask{
  Targets: taskEndpoints,
- Labels: map[string]string{
- "job": serviceIDMap[task.ServiceID].Spec.Name,
- },
+ Labels: taskLabels(task, serviceIDMap),
  }
- scrapeTasks = append(scrapeTasks, scrapetask)
 
+ scrapeTasks = append(scrapeTasks, scrapetask)
  }
 
  err = connectNetworks(allNetworks, prometheusContainerID)