mirror of
https://github.com/supabase/supabase.git
synced 2026-07-04 13:34:28 +08:00
45 lines
2.2 KiB
Plaintext
45 lines
2.2 KiB
Plaintext
---
|
|
id: realtime
|
|
title: Realtime
|
|
description: Using Supabase Realtime for multiplayer functionality.
|
|
sidebar_label: Overview
|
|
---
|
|
|
|
Supabase provides a Realtime API using [Realtime](https://github.com/supabase/realtime).
|
|
|
|
You can use this to:
|
|
|
|
- broadcast messages between users
|
|
- manage shared state between users
|
|
- listen to database changes over websockets
|
|
|
|
## Realtime Channels
|
|
|
|
In Realtime, everything is a [_channel_](https://hexdocs.pm/phoenix/channels.html).
|
|
Channels are like chatrooms where participants can join and leave—similar to Slack or Discord channels.
|
|
|
|
### Broadcast
|
|
|
|
Broadcast follows the classic Publisher/Subscriber pattern. A client (publisher) “broadcasts” messages using a unique identifier. For example, a user could send a message to a `#random` channel.
|
|
|
|
Other clients (subscribers) can “listen” to these messages in real-time, using the unique identifier. If they are listening to the `#random` channel, then they will receive the message.
|
|
|
|
A common use-case for Broadcast is sharing a user's cursor position with other clients in an online game.
|
|
|
|
### Presence
|
|
|
|
Presence synchronizes shared state between users.
|
|
Presence is very similar to Broadcast, except that the state is “persisted” in the Channel
|
|
so that new joiners immediately receive the state without waiting for another user to broadcast it.
|
|
In our Slack example, when you turn on Slack you can see who's online without each individual user
|
|
sending an “I'm online” message to the new-joiner. Presence utilizes Broadcast as the transport layer.
|
|
|
|
The neat thing about Presence is that if a user is suddenly disconnected (for example, they go offline), their state will be automatically removed from the shared state.
|
|
If you've ever tried to build an “I'm online” feature which handles unexpected disconnects, you'll appreciate how useful this is.
|
|
|
|
### Database changes
|
|
|
|
You can subscribe to database changes using Realtime.
|
|
The Realtime API works through PostgreSQL's replication functionality. Postgres sends database changes to a [publication](/docs/guides/database/replication#publications)
|
|
called `supabase_realtime`, and by managing this publication you can control which data is broadcast.
|