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Enhanced Depends Logic

GA

v2.9 and after

Introduction

Previous to version 2.8, the only way to specify dependencies in DAG templates was to use the dependencies field and specify a list of other tasks the current task depends on. This syntax was limiting because it does not allow the user to specify which result of the task to depend on. For example, a task may only be relevant to run if the dependent task succeeded (or failed, etc.).

Depends

To remedy this, there exists a new field called depends, which allows users to specify dependent tasks, their statuses, as well as any complex boolean logic. The field is a string field and the syntax is expression-like with operands having form <task-name>.<task-result>. Examples include task-1.Suceeded, task-2.Failed, task-3.Damenoed. The full list of available task results is as follows:

Task Result Description
.Succeeded Task Succeeded
.Failed Task Failed
.Errored Task Errored
.Skipped Task Skipped
.Daemoned Task is Daemoned and is not Pending

For convenience, if an omitted task result is equivalent to (task.Succeeded || task.Skipped || task.Daemoned).

For example:

depends: "task || task-2.Failed"

is equivalent to:

depends: (task.Succeeded || task.Skipped || task.Daemoned) || task-2.Failed

Full boolean logic is also available. Operators include:

  • &&
  • ||
  • !

Example:

depends: "(task-2.Succeeded || task-2.Skipped) && !task-3.Failed"

Compatibility with dependencies and dag.task.continueOn

This feature is fully compatible with dependencies and conversion is easy.

To convert simply join your dependencies with &&:

dependencies: ["A", "B", "C"]

is equivalent to:

depends: "A && B && C"

Because of the added control found in depends, the dag.task.continueOn is not available when using it. Furthermore, it is not possible to use both dependencies and depends in the same task group.