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Error handling: send Slack alert on failure
Trigger a Slack alert when a Kestra workflow fails. A simple, reusable failure notification pattern for monitoring production pipelines.
Categories
id: on-failure-alert
namespace: company.team
tasks:
- id: fail
type: io.kestra.plugin.scripts.shell.Commands
taskRunner:
type: io.kestra.plugin.core.runner.Process
commands:
- exit 1
errors:
- id: slack
type: io.kestra.plugin.slack.notifications.SlackIncomingWebhook
url: "{{ secret('SLACK_WEBHOOK') }}"
messageText: "Failure alert for flow {{ flow.namespace }}.{{ flow.id }} with ID
{{ execution.id }}"
Get notified in Slack the moment a workflow breaks. This blueprint shows the Kestra error-handling pattern: a flow runs its normal tasks, and if anything fails, the errors block fires a Slack message that names the namespace, flow ID, and execution ID so on-call engineers can jump straight to the failed run. It turns silent pipeline failures into actionable alerts and gives any team a reusable, copy-paste failure notification pattern for production monitoring.
How it works
- The main task
failis anio.kestra.plugin.scripts.shell.Commandstask running on theio.kestra.plugin.core.runner.Processrunner. Here it simply runsexit 1to simulate a failure, standing in for whatever real work your pipeline does. - When any task in the flow fails, Kestra runs the tasks declared under the top-level
errorsblock. - The error task
slackof typeio.kestra.plugin.slack.notifications.SlackIncomingWebhookposts to an incoming webhook URL pulled from a secret. - The
messageTextis templated with Pebble expressions ({{ flow.namespace }},{{ flow.id }},{{ execution.id }}) so each alert carries the exact context needed to find and debug the failed execution.
What you get
- Instant Slack notifications whenever a workflow fails.
- Alerts that include namespace, flow ID, and execution ID for fast triage.
- A drop-in
errorspattern you can paste into any flow. - No polling or external monitoring service to maintain.
Who it's for
- Data and platform engineers running production pipelines who need to know about failures fast.
- On-call and SRE teams that triage incidents from Slack.
- Anyone standardizing observability and alerting across many Kestra flows.
Why orchestrate this with Kestra
Slack has no idea your pipeline failed. Kestra closes that gap. The declarative errors block runs only on failure, with no extra cron job or babysitting script, and the alert is wired directly to execution lineage so the message links back to the exact run. Combine it with task retries to alert only after retries are exhausted, attach event triggers to chain recovery flows, and keep the whole pattern as version-controlled YAML that any team can reuse.
Prerequisites
- A running Kestra instance.
- The Slack plugin (bundled in the default Kestra distribution).
- A Slack incoming webhook URL for the channel that should receive alerts.
Secrets
SLACK_WEBHOOK: the Slack incoming webhook URL used by theslackerror task.
Quick start
- Create a Slack incoming webhook and copy its URL.
- Store it as the
SLACK_WEBHOOKsecret in your Kestra instance. - Add this flow and execute it. The
failtask runsexit 1, so the run fails on purpose. - Check your Slack channel for the alert naming the namespace, flow, and execution ID.
How to extend
- Replace the
failtask with your real pipeline logic and keep theerrorsblock as-is. - Add
retriesto your tasks so alerts fire only after retries are exhausted. - Customize
messageTextto add run duration, the failing task ID, or a direct link to the execution. - Add more error tasks (email, PagerDuty, a webhook) alongside Slack for layered alerting.
- Swap
SlackIncomingWebhookfor a richer Slack message task to post formatted blocks and buttons.
Links
Orchestrate with Kestra
Orchestrate Slack with KestraShare this Blueprint
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