Events in Tekton

Tekton’s controllers emits Kubernetes events when TaskRuns and PipelineRuns execute. This allows you to monitor and react to what’s happening during execution by retrieving those events using the kubectl describe command. Tekton can also emit CloudEvents.

Note: Conditions do not emit events but the underlying TaskRun do.

Events in TaskRuns

TaskRuns emit events for the following Reasons:

• Started: emitted the first time the TaskRun is picked by the reconciler from its work queue, so it only happens if webhook validation was successful. This event in itself does not indicate that a Step is executing; the Step executes once the following conditions are satisfied:
  • Validation of the Task and its associated resources must succeed, and
  • Checks for associated Conditions must succeed, and
  • Scheduling of the associated Pod must succeed.
• Succeeded: emitted once all steps in the TaskRun have executed successfully, including post-steps injected by Tekton.
• Failed: emitted if the TaskRun finishes running unsuccessfully because a Step failed, or the TaskRun timed out or was cancelled. A TaskRun also emits Failed events if it cannot execute at all due to failing validation.

Events in PipelineRuns

PipelineRuns emit events for the following Reasons:

• Started: emitted the first time the PipelineRun is picked by the reconciler from its work queue, so it only happens if webhook validation was successful. This event in itself does not indicate that a Step is executing; the Step executes once validation for the Pipeline as well as all associated Tasks and Resources is successful.
• Running: emitted when the PipelineRun passes validation and actually begins execution.
• Succeeded: emitted once all Tasks reachable via the DAG have executed successfully.
• Failed: emitted if the PipelineRun finishes running unsuccessfully because a Task failed or the PipelineRun timed out or was cancelled. A PipelineRun also emits Failed events if it cannot execute at all due to failing validation.

Events via CloudEvents

When you configure a sink, Tekton emits events as described in the table below.

Tekton sends cloud events in a parallel routine to allow for retries without blocking the reconciler. A routine is started every time the Succeeded condition changes - either state, reason or message. Retries are sent using an exponential back-off strategy. Because of retries, events are not guaranteed to be sent to the target sink in the order they happened.

CloudEvents for Runs are only sent when enabled in the configuration.

Note: CloudEvents for Runs rely on an ephemeral cache to avoid duplicate events. In case of controller restart, the cache is reset and duplicate events may be sent.

Format of CloudEvents

According to the CloudEvents spec, HTTP headers are included to match the context fields. For example:

"Ce-Id": "77f78ae7-ff6d-4e39-9d05-b9a0b7850527",
"Ce-Source": "/apis/tekton.dev/v1beta1/namespaces/default/taskruns/curl-run-6gplk",
"Ce-Specversion": "1.0",
"Ce-Subject": "curl-run-6gplk",
"Ce-Time": "2021-01-29T14:47:58.157819Z",
"Ce-Type": "dev.tekton.event.taskrun.unknown.v1",

Other HTTP headers are:

"Accept-Encoding": "gzip",
"Connection": "close",
"Content-Length": "3519",
"Content-Type": "application/json",
"User-Agent": "Go-http-client/1.1"

The payload is JSON, a map with a single root key taskRun or pipelineRun, depending on the source of the event. Inside the root key, the whole spec and status of the resource is included. For example:

{
  "taskRun": {
    "metadata": {
      "annotations": {
        "pipeline.tekton.dev/release": "v0.20.1",
        "tekton.dev/pipelines.minVersion": "0.12.1",
        "tekton.dev/tags": "search"
      },
      "creationTimestamp": "2021-01-29T14:47:57Z",
      "generateName": "curl-run-",
      "generation": 1,
      "labels": {
        "app.kubernetes.io/managed-by": "tekton-pipelines",
        "app.kubernetes.io/version": "0.1",
        "tekton.dev/task": "curl"
      },
      "managedFields": "(...)",
      "name": "curl-run-6gplk",
      "namespace": "default",
      "resourceVersion": "156770",
      "selfLink": "/apis/tekton.dev/v1beta1/namespaces/default/taskruns/curl-run-6gplk",
      "uid": "4ccb4f01-3ecc-4eb4-87e1-76f04efeee5c"
    },
    "spec": {
      "params": [
        {
          "name": "url",
          "value": "https://api.hub.tekton.dev/resource/96"
        }
      ],
      "resources": {},
      "serviceAccountName": "default",
      "taskRef": {
        "kind": "Task",
        "name": "curl"
      },
      "timeout": "1h0m0s"
    },
    "status": {
      "conditions": [
        {
          "lastTransitionTime": "2021-01-29T14:47:58Z",
          "message": "pod status \"Initialized\":\"False\"; message: \"containers with incomplete status: [place-tools]\"",
          "reason": "Pending",
          "status": "Unknown",
          "type": "Succeeded"
        }
      ],
      "podName": "curl-run-6gplk-pod",
      "startTime": "2021-01-29T14:47:57Z",
      "steps": [
        {
          "container": "step-curl",
          "name": "curl",
          "waiting": {
            "reason": "PodInitializing"
          }
        }
      ],
      "taskSpec": {
        "description": "This task performs curl operation to transfer data from internet.",
        "params": [
          {
            "description": "URL to curl'ed",
            "name": "url",
            "type": "string"
          },
          {
            "default": [],
            "description": "options of url",
            "name": "options",
            "type": "array"
          },
          {
            "default": "docker.io/curlimages/curl:7.72.0@sha256:3c3ff0c379abb1150bb586c7d55848ed4dcde4a6486b6f37d6815aed569332fe",
            "description": "option of curl image",
            "name": "curl-image",
            "type": "string"
          }
        ],
        "steps": [
          {
            "args": [
              "$(params.options[*])",
              "$(params.url)"
            ],
            "command": [
              "curl"
            ],
            "image": "$(params.curl-image)",
            "name": "curl",
            "resources": {}
          }
        ]
      }
    }
  }
}