Hooks¶

@dagster.success_hook(name=None, required_resource_keys=None)[source]¶

Create a hook on step success events with the specified parameters from the decorated function.

Parameters

name (Optional[str]) – The name of this hook.
required_resource_keys (Optional[AbstractSet[str]]) – Keys for the resources required by the hook.

Examples

@success_hook(required_resource_keys={'slack'})
def slack_message_on_success(context):
    message = 'solid {} succeeded'.format(context.solid.name)
    context.resources.slack.send_message(message)

@success_hook
def do_something_on_success(context):
    do_something()

@dagster.failure_hook(name=None, required_resource_keys=None)[source]¶

Create a hook on step failure events with the specified parameters from the decorated function.

Parameters

name (Optional[str]) – The name of this hook.
required_resource_keys (Optional[AbstractSet[str]]) – Keys for the resources required by the hook.

Examples

@failure_hook(required_resource_keys={'slack'})
def slack_message_on_failure(context):
    message = 'solid {} failed'.format(context.solid.name)
    context.resources.slack.send_message(message)

@failure_hook
def do_something_on_failure(context):
    do_something()

class dagster.HookDefinition(name, hook_fn, required_resource_keys=None, decorated_fn=None)[source]¶

Define a hook which can be triggered during a solid execution (e.g. a callback on the step execution failure event during a solid execution).

Parameters

name (str) – The name of this hook.
hook_fn (Callable) – The callback function that will be triggered.
required_resource_keys (Optional[AbstractSet[str]]) – Keys for the resources required by the hook.

class dagster.HookContext(step_execution_context, hook_def)[source]¶

The context object available to a hook function on an DagsterEvent.

log¶

Centralized log dispatch from user code.

Type: DagsterLogManager

hook_def¶

The hook that the context object belongs to.

Type: HookDefinition

solid¶

The solid instance associated with the hook.

Type: Solid

step_key¶

The key for the step where this hook is being triggered.

Type: str

resources¶

Resources available in the hook context.

Type: Resources

solid_config¶

The parsed config specific to this solid.

Type: Any

pipeline_name¶

The name of the pipeline where this hook is being triggered.

Type: str

run_id¶

The id of the run where this hook is being triggered.

Type: str

mode_def¶

The mode with which the pipeline is being run.

Type: ModeDefinition

property solid_exception¶

The thrown exception in a failed solid.

Returns: the exception object, None if the solid execution succeeds.
Return type: Optional[BaseException]

property solid_output_values¶

The computed output values.

Returns a dictionary where keys are output names and the values are:

the output values in the normal case
a dictionary from mapping key to corresponding value in the mapped case

dagster.build_hook_context(resources=None, mode_def=None, solid=None)[source]¶

Builds hook context from provided parameters.

build_hook_context can be used as either a function or a context manager. If there is a provided resource to build_hook_context that is a context manager, then it must be used as a context manager. This function can be used to provide the context argument to the invocation of a hook definition.

Parameters

resources (Optional[Dict[str, Any]]) – The resources to provide to the context. These can either be values or resource definitions.
mode_def (Optional[ModeDefinition]) – The mode definition used with the context.
solid (Optional[SolidDefinition, PendingNodeInvocation]) – The solid definition which the hook may be associated with.

Examples

context = build_hook_context()
hook_to_invoke(context)

with build_hook_context(resources={"foo": context_manager_resource}) as context:
    hook_to_invoke(context)