Enhanced Depends Logic¶
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.Daemoned. The full list of
available task results is as follows:
| Task Result | Description | Meaning |
|---|---|---|
.Succeeded |
Task Succeeded | Task finished with no error |
.Failed |
Task Failed | Task exited with a non-0 exit code |
.Errored |
Task Errored | Task had an error other than a non-0 exit code |
.Skipped |
Task Skipped | Task was skipped |
.Omitted |
Task Omitted | Task was omitted |
.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"
In the case that you're depending on a task that uses withItems, you can depend on
whether any of the item tasks are successful or all have failed using .AnySucceeded and .AllFailed, for example:
depends: "task-1.AnySucceeded || task-2.AllFailed"
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.