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Overview

This is the documentation for an experimental new system for writing bots that react to messages.

This directory contains library code for running Zulip bots that react to messages sent by users.

This document explains how to run the code, and it also talks about the architecture for creating bots.

Design goals

The goal is to have a common framework for hosting a bot that reacts to messages in any of the following settings:

Run as a long-running process using call_on_each_event (implemented today).
Run via a simple web service that can be deployed to PAAS providers and handles outgoing webhook requests from Zulip.
Embedded into the Zulip server (so that no hosting is required), which would be done for high quality, reusable bots; we would have a nice "bot store" sort of UI for browsing and activating them.

Running bots

Here is an example of running the "follow-up" bot from inside a Zulip repo:

cd ~/zulip/contrib_bots
./run.py lib/followup.py --config-file ~/.zuliprc-prod

Once the bot code starts running, you will see a message explaining how to use the bot, as well as some log messages. You can use the --quiet option to suppress these messages.

The bot code will run continuously until you kill them with control-C (or otherwise).

Configuration

For this document we assume you have some prior experience with using the Zulip API, but here is a quick review of what a .zuliprc files looks like. You can connect to the API as your own human user, or you can go into the Zulip settings page to create a user-owned bot.

[api]
email=someuser@example.com
key=<your api key>
site=https://zulip.somewhere.com

Architecture

In order to make bot development easy, we separate out boilerplate code (loading up the Client API, etc.) from bot-specific code (do what makes the bot unique).

All of the boilerplate code lives in ../run.py. The runner code does things like find where it can import the Zulip API, instantiate a client with correct credentials, set up the logging level, find the library code for the specific bot, etc.

Then, for bot-specific logic, you will find .py files in the lib directory (i.e. the same directory as the document you are reading now).

Each bot library simply needs to do the following:

Define a class that supports the methods usage, triage_message, and handle_message.
Set handler_class to be the name of that class.

(We make this a two-step process, so that you can give a descriptive name to your handler class.)

Portability

Creating a handler class for each bot allows your bot code to be more portable. For example, if you want to use your bot code in some other kind of bot platform, then if all of your bots conform to the handler_class protocol, you can write simple adapter code to use them elsewhere.

Another future direction to consider is that Zulip will eventually support running certain types of bots on the server side, to essentially implement post-send hooks and things of those nature.

Conforming to the handler_class protocol will make it easier for Zulip admins to integrate custom bots.

In particular, run.py already passes in instances of a restricted variant of the Client class to your library code, which helps you ensure that your bot does only things that would be acceptable for running in a server-side environment.

Other approaches

If you are not interested in running your bots on the server, then you can still use the full Zulip API. The hope, though, is that this architecture will make writing simple bots a quick/easy process.

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