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Chapter 18. Developing Precision Time Protocol events consumer applications

When developing consumer applications that make use of Precision Time Protocol (PTP) events on a bare-metal cluster node, you need to deploy your consumer application and a cloud-event-proxy container in a separate application pod. The cloud-event-proxy container receives the events from the PTP Operator pod and passes it to the consumer application. The consumer application subscribes to the events posted in the cloud-event-proxy container by using a REST API.

For more information about deploying PTP events applications, see About the PTP fast event notifications framework.

Note

The following information provides general guidance for developing consumer applications that use PTP events. A complete events consumer application example is outside the scope of this information.

18.1. PTP events consumer application reference
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PTP event consumer applications require the following features:

  1. A web service running with a POST handler to receive the cloud native PTP events JSON payload
  2. A createSubscription function to subscribe to the PTP events producer
  3. A getCurrentState function to poll the current state of the PTP events producer

The following example Go snippets illustrate these requirements:

Example PTP events consumer server function in Go

func server() {
  http.HandleFunc("/event", getEvent)
  http.ListenAndServe("localhost:8989", nil)
}

func getEvent(w http.ResponseWriter, req *http.Request) {
  defer req.Body.Close()
  bodyBytes, err := io.ReadAll(req.Body)
  if err != nil {
    log.Errorf("error reading event %v", err)
  }
  e := string(bodyBytes)
  if e != "" {
    processEvent(bodyBytes)
    log.Infof("received event %s", string(bodyBytes))
  } else {
    w.WriteHeader(http.StatusNoContent)
  }
}
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Example PTP events createSubscription function in Go

import (
"github.com/redhat-cne/sdk-go/pkg/pubsub"
"github.com/redhat-cne/sdk-go/pkg/types"
v1pubsub "github.com/redhat-cne/sdk-go/v1/pubsub"
)

// Subscribe to PTP events using REST API
s1,_:=createsubscription("/cluster/node/<node_name>/sync/sync-status/os-clock-sync-state")
1 

s2,_:=createsubscription("/cluster/node/<node_name>/sync/ptp-status/ptp-clock-class-change")
s3,_:=createsubscription("/cluster/node/<node_name>/sync/ptp-status/lock-state")

// Create PTP event subscriptions POST
func createSubscription(resourceAddress string) (sub pubsub.PubSub, err error) {
  var status int
      apiPath:= "/api/ocloudNotifications/v1/"
      localAPIAddr:=localhost:8989 // vDU service API address
      apiAddr:= "localhost:8089" // event framework API address

  subURL := &types.URI{URL: url.URL{Scheme: "http",
    Host: apiAddr
    Path: fmt.Sprintf("%s%s", apiPath, "subscriptions")}}
  endpointURL := &types.URI{URL: url.URL{Scheme: "http",
    Host: localAPIAddr,
    Path: "event"}}

  sub = v1pubsub.NewPubSub(endpointURL, resourceAddress)
  var subB []byte

  if subB, err = json.Marshal(&sub); err == nil {
    rc := restclient.New()
    if status, subB = rc.PostWithReturn(subURL, subB); status != http.StatusCreated {
      err = fmt.Errorf("error in subscription creation api at %s, returned status %d", subURL, status)
    } else {
      err = json.Unmarshal(subB, &sub)
    }
  } else {
    err = fmt.Errorf("failed to marshal subscription for %s", resourceAddress)
  }
  return
}
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1
Replace <node_name> with the FQDN of the node that is generating the PTP events. For example, compute-1.example.com.

Example PTP events consumer getCurrentState function in Go

//Get PTP event state for the resource
func getCurrentState(resource string) {
  //Create publisher
  url := &types.URI{URL: url.URL{Scheme: "http",
    Host: localhost:8989,
    Path: fmt.SPrintf("/api/ocloudNotifications/v1/%s/CurrentState",resource}}
  rc := restclient.New()
  status, event := rc.Get(url)
  if status != http.StatusOK {
    log.Errorf("CurrentState:error %d from url %s, %s", status, url.String(), event)
  } else {
    log.Debugf("Got CurrentState: %s ", event)
  }
}
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18.2. Reference cloud-event-proxy deployment and service CRs
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Use the following example cloud-event-proxy deployment and subscriber service CRs as a reference when deploying your PTP events consumer application.

Note

HTTP transport is the default transport for PTP and bare-metal events. Use HTTP transport instead of AMQP for PTP and bare-metal events where possible. AMQ Interconnect is EOL from 30 June 2024. Extended life cycle support (ELS) for AMQ Interconnect ends 29 November 2029. For more information see, Red Hat AMQ Interconnect support status.

Reference cloud-event-proxy deployment with HTTP transport

apiVersion: apps/v1
kind: Deployment
metadata:
  name: event-consumer-deployment
  namespace: <namespace>
  labels:
    app: consumer
spec:
  replicas: 1
  selector:
    matchLabels:
      app: consumer
  template:
    metadata:
      labels:
        app: consumer
    spec:
      serviceAccountName: sidecar-consumer-sa
      containers:
        - name: event-subscriber
          image: event-subscriber-app
        - name: cloud-event-proxy-as-sidecar
          image: openshift4/ose-cloud-event-proxy
          args:
            - "--metrics-addr=127.0.0.1:9091"
            - "--store-path=/store"
            - "--transport-host=consumer-events-subscription-service.cloud-events.svc.cluster.local:9043"
            - "--http-event-publishers=ptp-event-publisher-service-NODE_NAME.openshift-ptp.svc.cluster.local:9043"
            - "--api-port=8089"
          env:
            - name: NODE_NAME
              valueFrom:
                fieldRef:
                  fieldPath: spec.nodeName
            - name: NODE_IP
              valueFrom:
                fieldRef:
                  fieldPath: status.hostIP
              volumeMounts:
                - name: pubsubstore
                  mountPath: /store
          ports:
            - name: metrics-port
              containerPort: 9091
            - name: sub-port
              containerPort: 9043
          volumes:
            - name: pubsubstore
              emptyDir: {}
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Reference cloud-event-proxy deployment with AMQ transport

apiVersion: apps/v1
kind: Deployment
metadata:
  name: cloud-event-proxy-sidecar
  namespace: cloud-events
  labels:
    app: cloud-event-proxy
spec:
  selector:
    matchLabels:
      app: cloud-event-proxy
  template:
    metadata:
      labels:
        app: cloud-event-proxy
    spec:
      nodeSelector:
        node-role.kubernetes.io/worker: ""
      containers:
        - name: cloud-event-sidecar
          image: openshift4/ose-cloud-event-proxy
          args:
            - "--metrics-addr=127.0.0.1:9091"
            - "--store-path=/store"
            - "--transport-host=amqp://router.router.svc.cluster.local"
            - "--api-port=8089"
          env:
            - name: <node_name>
              valueFrom:
                fieldRef:
                  fieldPath: spec.nodeName
            - name: <node_ip>
              valueFrom:
                fieldRef:
                  fieldPath: status.hostIP
          volumeMounts:
            - name: pubsubstore
              mountPath: /store
          ports:
            - name: metrics-port
              containerPort: 9091
            - name: sub-port
              containerPort: 9043
          volumes:
            - name: pubsubstore
              emptyDir: {}
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Reference cloud-event-proxy subscriber service

apiVersion: v1
kind: Service
metadata:
  annotations:
    prometheus.io/scrape: "true"
    service.alpha.openshift.io/serving-cert-secret-name: sidecar-consumer-secret
  name: consumer-events-subscription-service
  namespace: cloud-events
  labels:
    app: consumer-service
spec:
  ports:
    - name: sub-port
      port: 9043
  selector:
    app: consumer
  clusterIP: None
  sessionAffinity: None
  type: ClusterIP
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18.3. PTP events available from the cloud-event-proxy sidecar REST API
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PTP events consumer applications can poll the PTP events producer for the following PTP timing events.

Expand
Table 18.1. PTP events available from the cloud-event-proxy sidecar
Resource URIDescription

/cluster/node/<node_name>/sync/ptp-status/lock-state

Describes the current status of the PTP equipment lock state. Can be in LOCKED, HOLDOVER, or FREERUN state.

/cluster/node/<node_name>/sync/sync-status/os-clock-sync-state

Describes the host operating system clock synchronization state. Can be in LOCKED or FREERUN state.

/cluster/node/<node_name>/sync/ptp-status/ptp-clock-class-change

Describes the current state of the PTP clock class.

18.4. Subscribing the consumer application to PTP events
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Before the PTP events consumer application can poll for events, you need to subscribe the application to the event producer.

18.4.1. Subscribing to PTP lock-state events
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To create a subscription for PTP lock-state events, send a POST action to the cloud event API at http://localhost:8081/api/ocloudNotifications/v1/subscriptions with the following payload: 

{
"endpointUri": "http://localhost:8989/event",
"resource": "/cluster/node/<node_name>/sync/ptp-status/lock-state",
}
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Example response

{
"id": "e23473d9-ba18-4f78-946e-401a0caeff90",
"endpointUri": "http://localhost:8989/event",
"uriLocation": "http://localhost:8089/api/ocloudNotifications/v1/subscriptions/e23473d9-ba18-4f78-946e-401a0caeff90",
"resource": "/cluster/node/<node_name>/sync/ptp-status/lock-state",
}
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18.4.2. Subscribing to PTP os-clock-sync-state events
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To create a subscription for PTP os-clock-sync-state events, send a POST action to the cloud event API at http://localhost:8081/api/ocloudNotifications/v1/subscriptions with the following payload: 

{
"endpointUri": "http://localhost:8989/event",
"resource": "/cluster/node/<node_name>/sync/sync-status/os-clock-sync-state",
}
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Example response

{
"id": "e23473d9-ba18-4f78-946e-401a0caeff90",
"endpointUri": "http://localhost:8989/event",
"uriLocation": "http://localhost:8089/api/ocloudNotifications/v1/subscriptions/e23473d9-ba18-4f78-946e-401a0caeff90",
"resource": "/cluster/node/<node_name>/sync/sync-status/os-clock-sync-state",
}
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18.4.3. Subscribing to PTP ptp-clock-class-change events
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To create a subscription for PTP ptp-clock-class-change events, send a POST action to the cloud event API at http://localhost:8081/api/ocloudNotifications/v1/subscriptions with the following payload: 

{
"endpointUri": "http://localhost:8989/event",
"resource": "/cluster/node/<node_name>/sync/ptp-status/ptp-clock-class-change",
}
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Example response

{
"id": "e23473d9-ba18-4f78-946e-401a0caeff90",
"endpointUri": "http://localhost:8989/event",
"uriLocation": "http://localhost:8089/api/ocloudNotifications/v1/subscriptions/e23473d9-ba18-4f78-946e-401a0caeff90",
"resource": "/cluster/node/<node_name>/sync/ptp-status/ptp-clock-class-change",
}
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18.5. Getting the current PTP clock status
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To get the current PTP status for the node, send a GET action to one of the following event REST APIs:

  • http://localhost:8081/api/ocloudNotifications/v1/cluster/node/<node_name>/sync/ptp-status/lock-state/CurrentState
  • http://localhost:8081/api/ocloudNotifications/v1/cluster/node/<node_name>/sync/sync-status/os-clock-sync-state/CurrentState
  • http://localhost:8081/api/ocloudNotifications/v1/cluster/node/<node_name>/sync/ptp-status/ptp-clock-class-change/CurrentState

The response is a cloud native event JSON object. For example:

Example lock-state API response

{
  "id": "c1ac3aa5-1195-4786-84f8-da0ea4462921",
  "type": "event.sync.ptp-status.ptp-state-change",
  "source": "/cluster/node/compute-1.example.com/sync/ptp-status/lock-state",
  "dataContentType": "application/json",
  "time": "2023-01-10T02:41:57.094981478Z",
  "data": {
    "version": "v1",
    "values": [
      {
        "resource": "/cluster/node/compute-1.example.com/ens5fx/master",
        "dataType": "notification",
        "valueType": "enumeration",
        "value": "LOCKED"
      },
      {
        "resource": "/cluster/node/compute-1.example.com/ens5fx/master",
        "dataType": "metric",
        "valueType": "decimal64.3",
        "value": "29"
      }
    ]
  }
}
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18.6. Verifying that the PTP events consumer application is receiving events
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Verify that the cloud-event-proxy container in the application pod is receiving PTP events.

Prerequisites

  • You have installed the OpenShift CLI (oc).
  • You have logged in as a user with cluster-admin privileges.
  • You have installed and configured the PTP Operator.

Procedure

  1. Get the list of active linuxptp-daemon pods. Run the following command: 

    $ oc get pods -n openshift-ptp
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    Example output

    NAME                    READY   STATUS    RESTARTS   AGE
linuxptp-daemon-2t78p   3/3     Running   0          8h
linuxptp-daemon-k8n88   3/3     Running   0          8h
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  2. Access the metrics for the required consumer-side cloud-event-proxy container by running the following command: 

    $ oc exec -it <linuxptp-daemon> -n openshift-ptp -c cloud-event-proxy -- curl 127.0.0.1:9091/metrics
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    where:

    <linuxptp-daemon>

    Specifies the pod you want to query, for example, linuxptp-daemon-2t78p.

    Example output

    # HELP cne_transport_connections_resets Metric to get number of connection resets
# TYPE cne_transport_connections_resets gauge
cne_transport_connection_reset 1
# HELP cne_transport_receiver Metric to get number of receiver created
# TYPE cne_transport_receiver gauge
cne_transport_receiver{address="/cluster/node/compute-1.example.com/ptp",status="active"} 2
cne_transport_receiver{address="/cluster/node/compute-1.example.com/redfish/event",status="active"} 2
# HELP cne_transport_sender Metric to get number of sender created
# TYPE cne_transport_sender gauge
cne_transport_sender{address="/cluster/node/compute-1.example.com/ptp",status="active"} 1
cne_transport_sender{address="/cluster/node/compute-1.example.com/redfish/event",status="active"} 1
# HELP cne_events_ack Metric to get number of events produced
# TYPE cne_events_ack gauge
cne_events_ack{status="success",type="/cluster/node/compute-1.example.com/ptp"} 18
cne_events_ack{status="success",type="/cluster/node/compute-1.example.com/redfish/event"} 18
# HELP cne_events_transport_published Metric to get number of events published by the transport
# TYPE cne_events_transport_published gauge
cne_events_transport_published{address="/cluster/node/compute-1.example.com/ptp",status="failed"} 1
cne_events_transport_published{address="/cluster/node/compute-1.example.com/ptp",status="success"} 18
cne_events_transport_published{address="/cluster/node/compute-1.example.com/redfish/event",status="failed"} 1
cne_events_transport_published{address="/cluster/node/compute-1.example.com/redfish/event",status="success"} 18
# HELP cne_events_transport_received Metric to get number of events received  by the transport
# TYPE cne_events_transport_received gauge
cne_events_transport_received{address="/cluster/node/compute-1.example.com/ptp",status="success"} 18
cne_events_transport_received{address="/cluster/node/compute-1.example.com/redfish/event",status="success"} 18
# HELP cne_events_api_published Metric to get number of events published by the rest api
# TYPE cne_events_api_published gauge
cne_events_api_published{address="/cluster/node/compute-1.example.com/ptp",status="success"} 19
cne_events_api_published{address="/cluster/node/compute-1.example.com/redfish/event",status="success"} 19
# HELP cne_events_received Metric to get number of events received
# TYPE cne_events_received gauge
cne_events_received{status="success",type="/cluster/node/compute-1.example.com/ptp"} 18
cne_events_received{status="success",type="/cluster/node/compute-1.example.com/redfish/event"} 18
# HELP promhttp_metric_handler_requests_in_flight Current number of scrapes being served.
# TYPE promhttp_metric_handler_requests_in_flight gauge
promhttp_metric_handler_requests_in_flight 1
# HELP promhttp_metric_handler_requests_total Total number of scrapes by HTTP status code.
# TYPE promhttp_metric_handler_requests_total counter
promhttp_metric_handler_requests_total{code="200"} 4
promhttp_metric_handler_requests_total{code="500"} 0
promhttp_metric_handler_requests_total{code="503"} 0
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