​Retries

Retries handle transient failures in your workflows.

They are defined at the task level and can be configured to retry a task a certain number of times, or with a certain delay between each retry.

What are retries

Kestra provides a task retry functionality. This makes it possible to add retry behavior for any failed task run based on configurations in the flow description.

A retry on a task run will create a new task run attempt.

Example

The following example defines a retry for the retry-sample task with a maximum of 5 attempts every 15 minutes:

- id: retry-sample
  type: io.kestra.core.tasks.log.Log
  message: my output for task {{task.id}}
  timeout: PT10M
  retry:
    type: constant
    maxAttempt: 5
    interval: PT15M

In next example, the flow will be retried four times every 0.25 ms, with each attempt executing for a maximum of 1 minute before being failed.

Due to the shell command logic used, it will succeed at the 5th attempt as we can track how many times it retries with {{ taskrun.attemptsCount }}

id: retry
namespace: io.kestra.demo
description:
  This flow will be retry 4 times and will success at the 5th attempts

tasks:
- id: failed
  type: io.kestra.plugin.scripts.shell.Commands
  runner: PROCESS
  commands:
  - 'if [ "{{taskrun.attemptsCount}}" -eq 4 ]; then exit 0; else exit 1; fi'
  retry:
    type: constant
    interval: PT0.25S
    maxAttempt: 5
    maxDuration: PT1M
    warningOnRetry: true

errors:
  - id: never-happen
    type: io.kestra.core.tasks.debugs.Return
    format: Never happened {{task.id}}

Retry options for all retry types

Duration

Some options above have to be filled with a duration notation. Durations are expressed in the ISO 8601 Durations format, here are some examples:

Retry types

constant

This establishes constant retry times: if the interval property is set to 10 minutes, it retries every 10 minutes.

exponential

This establishes retry behavior that waits longer between each retry e.g. 1s, 5s, 15s, ...

random

This establishes retries with a random delay between minimum and maximum limits.

Configuring retries globally

You can also configure retries globally for all tasks in a flow by using the plugins configuration:

kestra:
  plugins:
    configurations:
      - type: io.kestra
        values:
          retry:
            type: constant
            maxAttempt: 3
            interval: PT30S

This configuration will apply a constant retry with a maximum of 3 attempts every 30 seconds to all tasks across all flows.

Retry vs. Restart vs. Replay

Automatic vs. manual

Retries ensure that failed task runs are automatically rerun within the same Execution. Apart from retries, defined within your flow code, you can also manually rerun the flow from the Flow Execution page in the UI using the Restart or Replay buttons.

Restart vs. Replay

While Restart will rerun failed tasks within the current Execution (i.e., without creating a new execution), a Replay would result in a completely new run with a different Execution ID than the initial run.

When you replay an Execution, a new execution gets created for the same flow. However, you can still track which Execution triggered this new run thanks to the Original Execution field:

Replay can be executed from any task, even if that task executed successfully. But note that when you trigger a replay from a specific failed task, it will still result in a new Execution running all tasks downstream of your chosen start task:

When you want to rerun only failed tasks, use Restart.

Summary: Retries vs. Restart vs. Replay

The table below summarizes the differences between a retry, restart and replay.