Hooks

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

Examples:

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

@success_hook
def do_something_on_success(context):
    do_something()

@dagster.failure_hook

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

Examples:

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

@failure_hook
def do_something_on_failure(context):
    do_something()

class dagster.HookDefinition

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

class dagster.HookContext

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

property hook_def: The hook that the context object belongs to.

property instance: The instance configured to run the current job.

property job_name: The name of the job where this hook is being triggered.

property log: Centralized log dispatch from user code.

property op_config: The parsed config specific to this op.

property op_exception: The thrown exception in a failed op.

property op_output_metadata

The applied output metadata.

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

the applied output metadata in the normal case
a dictionary from mapping key to corresponding metadata in the mapped case

property op_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

property required_resource_keys: Resources required by this hook.

property resources: Resources available in the hook context.

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

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

dagster.build_hook_context

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
op (Optional[OpDefinitionOpDefinition, PendingNodeInvocation]) – The op definition which the
run_id (Optional[str]) – The id of the run in which the hook is invoked (provided for mocking purposes).
job_name (Optional[str]) – The name of the job in which the hook is used (provided for mocking purposes).
op_exception (Optional[Exception]) – The exception that caused the hook to be triggered.
instance (Optional[DagsterInstanceDagsterInstance]) – The Dagster instance configured to run the hook.

Examples:

context = build_hook_context()
hook_to_invoke(context)

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