mirror of https://github.com/vector-im/riot-web
40 lines
2.1 KiB
Markdown
40 lines
2.1 KiB
Markdown
|
# Local echo (developer docs)
|
||
|
|
|
||
|
|
The React SDK provides some local echo functionality to allow for components to do something
|
||
|
|
quickly and fall back when it fails. This is all available in the `local-echo` directory within
|
||
|
|
`stores`.
|
||
|
|
|
||
|
|
Echo is handled in EchoChambers, with `GenericEchoChamber` being the base implementation for all
|
||
|
|
chambers. The `EchoChamber` class is provided as semantic access to a `GenericEchoChamber`
|
||
|
|
implementation, such as the `RoomEchoChamber` (which handles echoable details of a room).
|
||
|
|
|
||
|
|
Anything that can be locally echoed will be provided by the `GenericEchoChamber` implementation.
|
||
|
|
The echo chamber will also need to deal with external changes, and has full control over whether
|
||
|
|
or not something has successfully been echoed.
|
||
|
|
|
||
|
|
An `EchoContext` is provided to echo chambers (usually with a matching type: `RoomEchoContext`
|
||
|
|
gets provided to a `RoomEchoChamber` for example) with details about their intended area of
|
||
|
|
effect, as well as manage `EchoTransaction`s. An `EchoTransaction` is simply a unit of work that
|
||
|
|
needs to be locally echoed.
|
||
|
|
|
||
|
|
The `EchoStore` manages echo chamber instances, builds contexts, and is generally less semantically
|
||
|
|
accessible than the `EchoChamber` class. For separation of concerns, and to try and keep things
|
||
|
|
tidy, this is an intentional design decision.
|
||
|
|
|
||
|
|
**Note**: The local echo stack uses a "whenable" pattern, which is similar to thenables and
|
||
|
|
`EventEmitter`. Whenables are ways of actioning a changing condition without having to deal
|
||
|
|
with listeners being torn down. Once the reference count of the Whenable causes garbage collection,
|
||
|
|
the Whenable's listeners will also be torn down. This is accelerated by the `IDestroyable` interface
|
||
|
|
usage.
|
||
|
|
|
||
|
|
## Audit functionality
|
||
|
|
|
||
|
|
The UI supports a "Server isn't responding" dialog which includes a partial audit log-like
|
||
|
|
structure to it. This is partially the reason for added complexity of `EchoTransaction`s
|
||
|
|
and `EchoContext`s - this information feeds the UI states which then provide direct retry
|
||
|
|
mechanisms.
|
||
|
|
|
||
|
|
The `EchoStore` is responsible for ensuring that the appropriate non-urgent toast (lower left)
|
||
|
|
is set up, where the dialog then drives through the contexts and transactions.
|
||
|
|
|