DocsWorkflow ComponentsErrors

Errors​Errors

Allow your flow to continue to operate despite errors.

There are multiple ways to handle errors in Kestra, to both help you identify them and allow flows to continue to operate despite errors.

errors Component

errors is a list of tasks set at the flow level that will be executed when an error occurs. You can add multiple tasks, and they will be executed sequentially. This is useful for sending alerts when errors occur.

The example below sends a flow-level failure alert via Slack using the SlackIncomingWebhook task defined using the errors property.

yaml
id: errors
namespace: company.team

description: This will always fail

tasks:
  - id: failed_task
    type: io.kestra.plugin.core.execution.Fail

errors:
  - id: alert_on_failure
    type: io.kestra.plugin.notifications.slack.SlackIncomingWebhook
    url: secret('SLACK_WEBHOOK')
    payload: |
      {
        "channel": "#alerts",
        "text": "Failure alert for flow {{ flow.namespace }}.{{ flow.id }} with ID {{ execution.id }}"
      }

Two kinds of error handlers can be defined:

  • Global: error handling global to a flow that must be at the root of the flow.
  • Local: error handling local to a Flowable Task, will handle errors for the flowable task and its children.

Global Error Handler

This flow example has a single task that fails immediately. The global error handler will then be called so the 2nd task will run.

yaml
id: errors
namespace: company.team

tasks:
  - id: failed
    type: io.kestra.plugin.core.execution.Fail

errors:
  - id: 2nd
    type: io.kestra.plugin.core.log.Log
    message: I'm failing {{task.id}}
    level: INFO

Local Error Handler

In this flow example, the error branch will be used only if a child of the task t2 has an error. If the task t1 failed, the error branch would not be used.

This can be useful to restrict error handling for a specific part of the flow and perform specific tasks like resource cleanup.

yaml
id: errors
namespace: company.team

tasks:
  - id: parent-seq
    type: io.kestra.plugin.core.flow.Sequential
    tasks:
      - id: t1
        type: io.kestra.plugin.core.debug.Return
        format: "{{task.id}} > {{taskrun.startDate}}"
      - id: t2
        type: io.kestra.plugin.core.flow.Sequential
        tasks:
          - id: t2-t1
            type: io.kestra.plugin.core.execution.Fail
        errors:
          - id: error-t1
            type: io.kestra.plugin.core.debug.Return
            format: "Error Trigger ! {{task.id}}"

allowFailure Property

When you execute a flow and one of its tasks fails, downstream tasks won't be executed. This may not always be desirable, especially for non-critical tasks. You can resolve this by adding the allowFailure property to the task, which will allow downstream tasks to continue despite the error. In this case, the execution will end in a WARNING state.

yaml
id: allow_failure
namespace: company.team

description: This flow will allow a failure of a task (imagine a flaky unit test) and will continue processing the last task, leaving the execution in a `WARNING` state.

tasks:
  - id: first
    type: io.kestra.plugin.core.debug.Return
    format: "{{task.id}} > {{taskrun.startDate}}"

  - id: allow_failure
    type: io.kestra.plugin.scripts.shell.Commands
    taskRunner:
      type: io.kestra.plugin.core.runner.Process
    allowFailure: true
    commands:
      - exit 1

  - id: last
    type: io.kestra.plugin.core.debug.Return
    format: "{{task.id}} > {{taskrun.startDate}}"

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