forked from GNUsocial/gnu-social
89 lines
4.1 KiB
Markdown
89 lines
4.1 KiB
Markdown
### Entrypoint
|
|
|
|
GNU social's entrypoint is the `public/index.php` script, which gets
|
|
called by the webserver for all requests. This is handled by the
|
|
webserver itself, which translates a `GET /foo` to `GET
|
|
/index.php?p=foo`. This feature is called 'fancy URLs', as it was in V2.
|
|
|
|
The `index` script handles all the initialization of the Symfony
|
|
framework and social itself. It reads configuration from `.env` or any
|
|
`.env.*` file at the project root. The `index` script creates a
|
|
`Kernel` object, which is defined on the `src/Kernel.php` file. This
|
|
is the part where the code we control starts; the `Kernel` constructor
|
|
creates the needed constants, sets the timezone to UTC and the string
|
|
encoding to UTF8. The other functions in this class get called by the
|
|
Symfony framework at the appropriate times. We will come back to this
|
|
file.
|
|
|
|
### Registering services
|
|
|
|
Next, the `src/Util/GNUsocial.php` class is instantiated by the
|
|
Symfony framework, on the `'onKernelRequest'` or `'onCommand'` events. The
|
|
former event, as described in the docs:
|
|
|
|
> This event is dispatched very early in Symfony, before the
|
|
> controller is determined. It's useful to add information to the
|
|
> Request or return a Response early to stop the handling of the
|
|
> request.
|
|
|
|
The latter, is launched on the `bin/console` script is used.
|
|
|
|
In both cases, these events call the `register` function, which
|
|
creates static references for the logging, event and translation
|
|
services. This is done so these services can be used via static
|
|
function calls, which is much less verbose and more accessible than
|
|
the way the framework recommends. This function also loads all the
|
|
Modules and Plugins, which like in V2, are components that aren't
|
|
directly connected to the core code, being used to implement internal
|
|
and optional functionality respectively, by handling events launched
|
|
by various parts of the code.
|
|
|
|
### Database definitions
|
|
|
|
Going back to the `Kernel`, the `build` function gets called by the
|
|
Symfony framework and allows us to register a 'Compiler Pass'.
|
|
Specifically, we register the `SchemaDefPass` from the
|
|
`src/DependencyInjection/Compiler/SchemaDefPass.php` file, which adds
|
|
a new 'metadata driver' to Doctrine. The metadata driver is
|
|
responsible for loading database definitions. We keep the same method
|
|
as in V2, which was that each 'Entity' has a `schemaDef` static
|
|
function which returns an array describing the database.
|
|
|
|
This definition is handled by the `SchemaDefDriver` class from
|
|
`src/Util/SchemaDefDriver.php` file, which extends `StaticPHPDriver`
|
|
and replaces the methods `loadMetadata` with `schemaDef`. The function
|
|
`loadMetadataForClass` function is called by the Symfony framework for
|
|
each file in `src/Entity/`. It allows us to call the `schemaDef`
|
|
function and translate the array definition to Doctrine's internal
|
|
representation.
|
|
|
|
### Routing
|
|
|
|
Next, we'll look at the `RouteLoader`, defined in
|
|
`src/Util/RoutLoader.php`, which loads all the files from
|
|
`src/Routes/*.php` and calls the static `load` method, which defines
|
|
routes with an interface similar to V2's `connect`, except it requires
|
|
an extra identifier as the first argument. This identifier is used,
|
|
for instance, to generate URLs for each route. Each route connects an
|
|
URL path to a Controller, with the possibility of taking arguments,
|
|
which are passed to the `__invoke` method of the respective
|
|
controller. The controllers are defined in `src/Controller/` and are
|
|
responsible for handling a request and return a Symfony `Response`
|
|
object (subject to change, in order to abstract HTML vs JSON output).
|
|
|
|
### End to end
|
|
|
|
The next steps are handled by the Symfony framework which creates a
|
|
`Request` object from the HTTP request, and then a corresponding
|
|
`Response` is created by calling the `Kernel::handle` method, which
|
|
matches the appropriate route and thus calls it's controller.
|
|
|
|
### Performance
|
|
|
|
All this happens on each request, which seems like a lot to handle,
|
|
and would be too slow. Fortunately, Symfony has a 'compiler' which
|
|
caches and optimizes the code paths. In production mode, this can be
|
|
done through a command, while in development mode, it's handled on
|
|
each request if the file changed, which has a performance impact, but
|
|
obviously makes development easier.
|