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128 lines
4.7 KiB
ReStructuredText
128 lines
4.7 KiB
ReStructuredText
*********************
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Software architecture
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*********************
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Limnoria abstracts its internal architecture away from plugins through
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its plugin API, which is enough most of the time.
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However, you may need want to understand its internal architecture, either
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to debug complex problems, provide advanced features that hook into
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the internals, contribute to the core, or simply out of curiosity.
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This guide will try to walk you through this, assuming you are already
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familiar with using the bot and writing plugins (if not, see the
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:ref:`capabilities` documentation, the :ref:`plugin-tutorial`,
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and :ref:`events`,
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You should also be somewhat familiar with the
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`IRC protocol <https://modern.ircdocs.horse/>`.
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.. note::
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This document is a work in progress and is still incomplete.
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As usual, feel free to ask any questions in #limnoria @ freenode.
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Main loop and drivers
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=====================
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The main event loop is a very classic synchronous loop.
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It is defined in :file:`scripts/supybot`, and essentially just this::
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while world.ircs:
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try:
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drivers.run()
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except KeyboardInterrupt:
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# Handle Ctrl-C (trigger shutdown)
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except:
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# Handle other unhandled errors
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Where :func:`drivers.run` does this::
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for (name, driver) in _drivers.items():
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if name not in _deadDrivers:
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driver.run()
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for name in _deadDrivers:
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# Remove the driver
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while _newDrivers:
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(name, driver) = _newDrivers.pop()
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# add the new driver
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Drivers are the sources of events in the main thread. In a normal Limnoria
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setup, there are two types of drivers: the Socket driver (which connects
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synchronously to IRC) and the :ref:`schedule driver <supybot-schedule>`
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(which runs functions periodically, like cron).
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Historically, there was an alternative driver to connect to IRC,
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based on Twisted. It was deprecated, then removed in 2019, because
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Python's ``socket`` module became as powerful as Twisted as it gained
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support for ``select()`` and TLS.
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Network drivers have a reference to a :class:`irclib.Irc` object, and
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do three things in their ``run()`` method:
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1. check the connection is still alive (and schedule a reconnect if not)
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2. get new messages from their :class:`irclib.Irc` instance (using
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:meth:`irclib.Irc.takeMsg`) and send them to the network
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3. get new messages from the network and pass them to their :class:`irclib.Irc`
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(using :meth:`irclib.Irc.feedMsg`)
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The actual implementation of the current ``Socket`` driver is actually
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a little more complex than this, as all ``Socket`` driver instances cooperate
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to use ``select()`` together, but this is the rough idea.
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See :file:`src/drivers/Socket.py` for details.
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irclib
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======
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As we saw above, network drivers pass their messages to a class defined in
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:mod:`irclib`, which is where most of the IRC protocol implementation is.
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Unlike most event-driven software (especially IRC implementation), Limnoria
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does not have hooks that are registered to call a function when a specific
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event/IRC command is received.
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Instead, event listeners receive all events, and inherit on
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:class:`supybot.irclib.IrcCommandDispatcher`, which calls a specific method
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based on the IRC command name. For example, it calls the ``doTopic`` method
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when receiving a ``TOPIC`` message.
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This dispatching is used both in the main IRC handling
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(:class:`supybot.irclib.Irc`) and plugins (via
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:class:`supybot.callbacks.PluginMixin`, which inherits
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:class:`supybot.irclib.IrcCommandDispatcher`).
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We saw above that the :class:`supybot.irclib.Irc` object receives messages
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directly from the driver. It's also in charge of keeping track of other
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callbacks (ie. plugins) via :meth:`supybot.irclib.Irc.addCallback` and passing
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every message to their ``__call__`` method (which then does the dispatching
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on its own again, as it inherits :class:`supybot.irclib.IrcCommandDispatcher`).
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As there are few callbacks (under a hundred plugins),
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this simple architecture is efficient enough.
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Additionally, when receiving a message and before sending one, it iterates
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through the list of plugins and calls their ``inFilter`` and ``outFilter``
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methods (respectively), if any.
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If you look at the code of :class:`supybot.irclib.Irc` and
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:class:`supybot.irclib.IrcState`, you see they are mostly made of ``doXxx``
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methods, which exhaustively implement every known IRC command, update some
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state, and optionally react to it by queuing messages.
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Commands
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========
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Next is the callbacks system, mostly implemented in :mod:``supybot.callbacks``.
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This is where all the magic happens to make plugins so easy to write;
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it's also the most complex part of Limnoria and the hardest to understand,
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because everything is tightly interleaved.
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TODO
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Registry
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========
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TODO
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Auto-documentation
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==================
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TODO
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