Signals

Okami includes a signal dispatcher which allows applications to get notified when actions occur somewhere in okami framework.

Signals allow certain senders to notify a set of receivers that some action has taken place.

They’re especially useful when many pieces of code may be interested in the same events.

Receiving signals

In code example below, function response_created connects to signal signals.response_created by being decorated with signals.receiver.

Function response_created will be called every time signal signals.response_created is executed.

from okami import signals

@signals.receiver(signals.response_created)
async def response_created(signal, sender, **kwargs):
    print("response_created: {}, {}, {}".format(signal, sender, kwargs))

Configuration

Configuration is a bit awkward because of the way python decorators work.

Make sure your signal receivers are imported at some point in your project otherwise add

from your.app import signals

somewhere, i.e. in your top __init__.py module.

Available signals

Okami provides a set of built-in signals.

Http middleware signals

• http_middleware_initialised
• http_middleware_started
• http_middleware_finished
• http_middleware_finalised

Spider middleware signals

• spider_middleware_initialised
• spider_middleware_started
• spider_middleware_finished
• spider_middleware_finalised

Downloader signals

• response_created

Startup pipeline signals

• startup_pipeline_initialised
• startup_pipeline_started
• startup_pipeline_finished
• startup_pipeline_finalised

Items pipeline signals

• items_pipeline_initialised
• items_pipeline_started
• items_pipeline_finished
• items_pipeline_finalised

Tasks pipeline signals

• tasks_pipeline_initialised
• tasks_pipeline_started
• tasks_pipeline_finished
• tasks_pipeline_finalised