slack-serverless 2024.1018

Simplified serverless Slack bot interactions

Utility library for serverless Slack apps

This is a (currently very simple) library that eases development of serverless Slack app and bots.

Currently, it targets Google Cloud Platform (but is easily generalised), and provides a decorator and some utility functions that make Slack signature verification automatic and help with building responses in a very lightweight fashion.

I will grow it with things I end up needing in my work, but if you have different needs and want to extend the library to support them, then PRs would be gratefully received!

MVP Example

This will accept any slash command you've configured for your bot, and just greet the user who calls it, tagging them in the reply.

from slack_serverless import slack_slash_command_gcp
from slack_messaging import slack_in_channel_text_response, slack_tags

@slack_slash_command_gcp(slack_signing_key=YOUR_SIGNING_KEY)
def command_handler(payload):
    return slack_in_channel_text_response(f"Hi there <@{slack_tags([payload['user_id']])}>")

Message Deferral

Note to avoid dependency conflicts, this library does not depend on the cloud provider APIs that are needed. For GCP, be sure to add google-cloud-pubsub>=2.18.1 to your requirements.txt (or whatever) if you're using deferral.

If you need to take more than three seconds to reply to a Slack message, the usual thing to do in a serverless environment is hand off the message to another function, and have the first one acknowledge receipt back to Slack within three seconds. This is required - failing to respond in a timely fashion will result in the user seeing an error message.

This library provides a comfort wrapper around this use case - all you need to do is set up a PubSub topic (or your cloud's equivalent, though only GCP is supported as yet) and defer the message in your main Slack handler with the slack_defer function.

You then have a second lambda, triggered by the pubsub (Eventarc or equivalent) in which the main function is decorated with @slack_deferred_slash_handler_gcp (despite the name, it supports both events and slash commands - it'll be changing soon) and handles the event.

This will take care of wrapping and unwrapping the event appropriately and generally trades of some ease of use for a little flexibility. If it doesn't meet your needs you can of course just ignore it and code up the functionality yourself.

AWS

AWS is supported (at least, Lambdas with API Gateway proxy triggers are), and it's much the same as for GCP - just use the slack_slash_command_aws_api_gateway_proxy and slack_event_webhook_aws_api_gateway_proxy decorators instead of the GCP ones, and you should be good to go.

Other Cloud Providers

Things will be a bit more manual here (but I'll happily add comfort wrappers if there's enough call and a PR that contributes them 😉).

The easiest thing to do is use the slack_slash_command decorator, which is similar to the gcp one above but needs you pass in a couple of Callables the code will use to get access to the data in a provider-specific way.

Take a look at the code in slack_serverless.py for examples to get you started.

Developing

Don't forget to set up pre-commit if you're developing things, especially if you plan to push a PR.

Legal Mumbo-Jumbo

Copyright (c)2023 Ross Bamford (and contributors)

License: MIT (see LICENSE.md for details).