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A simple plugin that can be used to speed plugin development by having the plugin under development be reloaded whenever its executable changes, or when triggered automatically. Signed-off-by: Christian Decker <decker.christian@gmail.com>
86 lines
3.5 KiB
Markdown
86 lines
3.5 KiB
Markdown
# Autoreload Plugin
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> You write the code, we do the rest!
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The autoreload plugin aims to help plugin developers to reload the plugin
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inside of `lightningd` without having to restart the entire daemon. It watches
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the executable file and will restart the plugin when a change is detected.
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The plugin adds the following command line options:
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- `--autoreload-plugin=path/to/plugin.py`: specifies which plugin you'd like
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`autoreload` to manage. The syntax was chosen so you can just prefix any
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existing `--plugin` with `autoreload` and start hacking.
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The plugin adds the following RPC methods:
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- `autoreload-restart`: triggers a manual restart of the plugin under
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development, useful if you want to reload because of a dependency change or
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you have a script that knows when a reload is needed. We will still
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autoreload whenever we detect a change in the executable.
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So in order to have a plugin `path/to/plugin.py` autoreload on changes you'll
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need to call `lightningd` with the following arguments:
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```bash
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lightningd --plugin=path/to/autoreload.py --autoreload-plugin=path/to/plugin.py
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```
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The first argument loads the `autoreload` plugin, and the second argument
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tells `autoreload` to load, watch and restart the plugin under development.
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## Install
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This plugin relies on the `pylightning` and the `psutil` libraries. You should
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be able to install these dependencies with `pip`:
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```bash
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pip3 install -r requirements.txt
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```
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You might need to also specify the `--user` command line flag depending on
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your environment.
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## How does it work?
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In order to hide the restarts from `lightningd` the autoreload plugin will
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insert itself between `lightningd` and the plugin that is to be reloaded,
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acting as an almost transparent proxy between the two. The only exception to
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this are the two calls to register and initialize the plugin:
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- `getmanifest` is captured and the autoreload RPC methods and options are
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injected, so `lightningd` knows about them and tells us when we get
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initialized.
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- `init` is captured and the options we returned above are stripped again,
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otherwise we might upset the plugin under development. We also cache it, so
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we can tell the plugin under development again when we restart it.
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Upon restarting we call `getmanifest` on the plugin under development just to
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be safe (though you wouldn't do any initialization before being told so with
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`init` would you? :wink:) and we then call `init` with the parameters we
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cached when we were initialized ourselves. After this initialization dance is
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complete, we will simply forward any calls directly to the plugin under
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development and forward any output it produces to `lightningd`.
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We watch the modification time of the executable file and automatically
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restart the plugin should it change. You can trigger this by changing the file
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or even just `touch`ing it on the filesystem. You can also trigger a manual
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restart using the `autoreload-restart` RPC method:
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```bash
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lightning-cli autoreload-restart
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```
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## Caveats :construction:
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- Only one plugin can currently be managed by the autoreload plugin.
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- Log lines will be prefixed with the autoreload plugin's name, not the
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plugin under development.
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- Since the registration of options, subscriptions, methods and hooks happens
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during startup in `lightningd` you cannot currently add or remove any of
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these without restarting `lightningd` itself. If you change them and have
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autoreload restart the plugin under development you might experience
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strange results.
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