Slackers

Slack webhooks API served by FastAPI

What is Slackers

Slackers is a FastAPI implementation to handle Slack interactions and events. It serves endpoints to receive slash commands, app actions, interactive components. It also listens for events sent to the Slack Events API Slack Events.

Installation

You can install Slackers with pip $ pip install slackers

Configuration

SLACK_SIGNING_SECRET

You must configure the slack signing secret. This will be used to verify the incoming requests signature.
$ export SLACK_SIGNING_SECRET=your_slack_signing_secret

Example usage

Slackers will listen for activity from the Events API on /events, for interactive components on /actions and for slash commands on /commands. When an interaction is received, it will emit an event. You can listen for these events as shown in the following examples.

On receiving a request, Slackers will emit an event which you can handle yourself. Slackers will also respond to Slack with an (empty) http 200 response telling Slack all is well received.

Starting the server

As said, Slackers uses the excellent FastAPI to serve it's endpoints. Since you're here, I'm assuming you know what FastAPI is, but if you don't, you can learn all about how that works with this tutorial.

Slackers offers you a router which you can include in your own FastAPI.

from fastapi import FastAPI
from slackers.server import router

app = FastAPI()
app.include_router(router)

# Optionally you can use a prefix
app.include_router(router, prefix='/slack')

Events

Once your server is running, the events endpoint is setup at /events, or if you use the prefix as shown above, on /slack/events.

Accepting the challenge

When setting up Slack to send events, it will first send a challenge to verify your endpoint. Slackers detects when a challenge is sent. You can simply start our api and Slackers will meet the challenge automatically.

Responding to events

On receiving an event, Slackers will emit a python event, which you can act upon as shown below.

import logging
from slackers.hooks import events

log = logging.getLogger(__name__)

@events.on("app_mention")
def handle_mention(payload):
    log.info("App was mentioned.")
    log.debug(payload)

Actions

Once your server is running, the actions endpoint is setup at /actions, or if you use the prefix as shown above, on /slack/actions.

Responding to actions

On receiving an action, Slackers will emit a python event, which you can listen for as shown below. You can listen for the action type, or more specifically for the action id or callback id linked to the action.

import logging
from slackers.hooks import actions

log = logging.getLogger(__name__)

# Listening for the action type.
@actions.on("block_actions")
def handle_action(payload):
    log.info("Action started.")
    log.debug(payload)

# Listen for an action by it's action_id
@actions.on("block_actions:your_action_id")
def handle_action_by_id(payload):
    log.info("Action started.")
    log.debug(payload)

# Listen for an action by it's callback_id
@actions.on("block_actions:your_callback_id")
def handle_action_by_callback_id(payload):
    log.info(f"Action started.")
    log.debug(payload)

Interactive messages

Interactive message actions do not have an action_id. They do have a name and a type. To act upon interactive messages, you can listen for the action type, interactive_message as wel as the combination of the interactive_message and name, type or both.

import logging
from slackers.hooks import actions

log = logging.getLogger(__name__)

# Listening for the action type.
@actions.on("interactive_message")
def handle_action(payload):
    log.info("Action started.")
    log.debug(payload)

# Listen for an action by it's name
@actions.on("interactive_message:action_name")
def handle_action_by_id(payload):
    log.info("Action started.")
    log.debug(payload)

# Listen for an action by it's type
@actions.on("interactive_message:action_type")
def handle_action_by_callback_id(payload):
    log.info(f"Action started.")
    log.debug(payload)

# Listen for an action by it's name and type
@actions.on("interactive_message:action_name:action_type")
def handle_action_by_callback_id(payload):
    log.info(f"Action started.")
    log.debug(payload)

Custom responses

Slackers tries to be fast to respond to Slack. The events you are listening for with the likes of @actions.on(...) are scheduled as an async task in a fire and forget fashion. After scheduling these events, Slackers will by default return an empty 200 response which might happen before the events are handled.

In some cases you might want to act on the payload and return a custom response to Slack. For this, you can use the slackers responder decorator to define your custom handler function. This function is then used as a callback instead of returning the default response. You must ensure your custom handler returns a starlette.responses.Response or one of it's subclasses. You must furthermore ensure that there is only one responder responding to your Slack request.

Please note that the events are also emitted, so you could have both @actions.on("block_action:xyz") and @responder("block_action:xyz"). Just keep in mind that the event emissions are async and are not awaited. In other words, Slackers doesn't ensure that the response (whether your custom response or the default) is returned before or after the events are emitted.

from starlette.responses import JSONResponse
from slackers.hooks import responder

@responder("block_actions:your_callback_id")
def custom_handler(payload):
    # handle your payload
    ...
    return JSONResponse(content={"custom": "Custom Response"})

Slash commands

Once your server is running, the commands endpoint is setup at /commands, or if you use the prefix as shown above, on /slack/commands. Slackers will emit an event with the name of the command, so if your command is /engage, you can listen for the event engage (without the slash)

Responding to slash commands

On receiving a command, Slackers will emit a python event, which you can listen for as shown below.

import logging
from slackers.hooks import commands

log = logging.getLogger(__name__)


@commands.on("engage")  # responds to "/engage"  
def handle_command(payload):
    log.info("Command received")
    log.debug(payload)

Async

Since events are emitted using pyee's Async event emitter, it is possible to define your event handlers as async functions. Just keep in mind that errors are in this case emitted on the 'error' event.

import logging
from slackers.hooks import commands

log = logging.getLogger(__name__)

@commands.on('error')
def log_error(exc):
    log.error(str(exc))


@commands.on("engage")  # responds to "/engage"  
async def handle_command(payload):
    ...