Supabase Realtime

Send ephemeral messages, track and synchronize shared state, and listen to Postgres changes all over WebSockets.
Multiplayer Demo · Request Feature · Report Bug

Status

Features	v1	v2	Status
Postgres Changes	✔	✔	GA
Broadcast		✔	Beta
Presence		✔	Beta

This repository focuses on version 2 but you can still access the previous version's code and Docker image. For the latest Docker images go to https://hub.docker.com/r/supabase/realtime.

The codebase is under heavy development and the documentation is constantly evolving. Give it a try and let us know what you think by creating an issue. Watch releases of this repo to get notified of updates. And give us a star if you like it!

Overview

What is this?

This is a server built with Elixir using the Phoenix Framework that enables the following functionality:

• Broadcast: Send ephemeral messages from client to clients with low latency.
• Presence: Track and synchronize shared state between clients.
• Postgres Changes: Listen to Postgres database changes and send them to authorized clients.

For a more detailed overview head over to Realtime guides.

Does this server guarantee message delivery?

The server does not guarantee that every message will be delivered to your clients so keep that in mind as you're using Realtime.

Quick start

You can check out the Multiplayer demo that features Broadcast, Presence and Postgres Changes under the demo directory: https://github.com/supabase/realtime/tree/main/demo.

Client libraries

• JavaScript: @supabase/realtime-js
• Dart: @supabase/realtime-dart

Server Setup

To get started, spin up your Postgres database and Realtime server containers defined in docker-compose.yml. As an example, you may run docker-compose -f docker-compose.yml up.

Note Supabase runs Realtime in production with a separate database that keeps track of all tenants. However, a schema, _realtime, is created when spinning up containers via docker-compose.yml to simplify local development.

A tenant has already been added on your behalf. You can confirm this by checking the _realtime.tenants and _realtime.extensions tables inside the database.

You can add your own by making a POST request to the server. You must change both name and external_id while you may update other values as you see fit:

  curl -X POST \
  -H 'Content-Type: application/json' \
  -H 'Authorization: Bearer eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJpc3MiOiIiLCJpYXQiOjE2NzEyMzc4NzMsImV4cCI6MTcwMjc3Mzk5MywiYXVkIjoiIiwic3ViIjoiIn0._ARixa2KFUVsKBf3UGR90qKLCpGjxhKcXY4akVbmeNQ' \
  -d $'{
    "tenant" : {
      "name": "realtime-dev",
      "external_id": "realtime-dev",
      "jwt_secret": "a1d99c8b-91b6-47b2-8f3c-aa7d9a9ad20f",
      "extensions": [
        {
          "type": "postgres_cdc_rls",
          "settings": {
            "db_name": "postgres",
            "db_host": "host.docker.internal",
            "db_user": "postgres",
            "db_password": "postgres",
            "db_port": "5432",
            "region": "us-west-1",
            "poll_interval_ms": 100,
            "poll_max_record_bytes": 1048576,
          }
        }
      ]
    }
  }' \
  http://localhost:4000/api/tenants

Note The Authorization token is signed with the secret set by API_JWT_SECRET in docker-compose.yml.

If you want to listen to Postgres changes, you can create a table and then add the table to the supabase_realtime publication:

create table test (
  id serial primary key
);

alter publication supabase_realtime add table test;

You can start playing around with Broadcast, Presence, and Postgres Changes features either with the client libs (e.g. @supabase/realtime-js), or use the built in Realtime Inspector on localhost, http://localhost:4000/inspector/new (make sure the port is correct for your development environment).

The WebSocket URL must contain the subdomain, external_id of the tenant on the _realtime.tenants table, and the token must be signed with the jwt_secret that was inserted along with the tenant.

If you're using the default tenant, the URL is ws://realtime-dev.localhost:4000/socket (make sure the port is correct for your development environment), and you can use eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJleHAiOjE3MDMwMjgwODcsInJvbGUiOiJwb3N0Z3JlcyJ9.tz_XJ89gd6bN8MBpCl7afvPrZiBH6RB65iA1FadPT3Y for the token. The token must have exp and role (database role) keys.

Environment Variables

Variable	Type	Description
PORT	number	Port which you can connect your client/listeners
DB_HOST	string	Database host URL
DB_PORT	number	Database port
DB_USER	string	Database user
DB_PASSWORD	string	Database password
DB_NAME	string	Postgres database name
DB_ENC_KEY	string	Key used to encrypt sensitive fields in _realtime.tenants and _realtime.extensions tables. Recommended: 16 characters.
DB_AFTER_CONNECT_QUERY	string	Query that is run after server connects to database.
API_JWT_SECRET	string	Secret that is used to sign tokens used to manage tenants and their extensions via HTTP requests.
SECRET_KEY_BASE	string	Secret used by the server to sign cookies. Recommended: 64 characters.
ERL_AFLAGS	string	Set to either "-proto_dist inet_tcp" or "-proto_dist inet6_tcp" depending on whether or not your network uses IPv4 or IPv6, respectively.
APP_NAME	string	A name of the server.
DNS_NODES	string	Node name used when running server in a cluster.
MAX_CONNECTIONS	string	Set the soft maximum for WebSocket connections. Defaults to '16384'.
MAX_HEADER_LENGTH	string	Set the maximum header length for connections (in bytes). Defaults to '4096'.
NUM_ACCEPTORS	string	Set the number of server processes that will relay incoming WebSocket connection requests. Defaults to '100'.
DB_QUEUE_TARGET	string	Maximum time to wait for a connection from the pool. Defaults to '5000' or 5 seconds. See for more info: DBConnection.
DB_QUEUE_INTERVAL	string	Interval to wait to check if all connections were checked out under DB_QUEUE_TARGET. If all connections surpassed the target during this interval than the target is doubled. Defaults to '5000' or 5 seconds. See for more info: DBConnection.
DB_POOL_SIZE	string	Sets the number of connections in the database pool. Defaults to '5'.
SLOT_NAME_SUFFIX	string	This is appended to the replication slot which allows making a custom slot name. May contain lowercase letters, numbers, and the underscore character. Together with the default supabase_realtime_replication_slot, slot name should be up to 64 characters long.
TENANT_MAX_BYTES_PER_SECOND	string	The default value of maximum bytes per second that each tenant can support, used when creating a tenant for the first time. Defaults to '100_000'.
TENANT_MAX_CHANNELS_PER_CLIENT	string	The default value of maximum number of channels each tenant can support, used when creating a tenant for the first time. Defaults to '100'.
TENANT_MAX_CONCURRENT_USERS	string	The default value of maximum concurrent users per channel that each tenant can support, used when creating a tenant for the first time. Defaults to '200'.
TENANT_MAX_EVENTS_PER_SECOND	string	The default value of maximum events per second that each tenant can support, used when creating a tenant for the first time. Defaults to '100'.
TENANT_MAX_JOINS_PER_SECOND	string	The default value of maximum channel joins per second that each tenant can support, used when creating a tenant for the first time. Defaults to '100'.
SEED_SELF_HOST	boolean	Seeds the system with default tenant

WebSocket URL

The WebSocket URL is in the following format for local development: ws://[external_id].localhost:4000/socket/websocket

If you're using Supabase's hosted Realtime in production the URL is wss://[project-ref].supabase.co/realtime/v1/websocket?apikey=[anon-token]&log_level=info&vsn=1.0.0"

WebSocket Connection Authorization

WebSocket connections are authorized via symmetric JWT verification. Only supports JWTs signed with the following algorithms:

• HS256
• HS384
• HS512

Verify JWT claims by setting JWT_CLAIM_VALIDATORS:

e.g. {'iss': 'Issuer', 'nbf': 1610078130}

Then JWT's "iss" value must equal "Issuer" and "nbf" value must equal 1610078130.

Note:

JWT expiration is checked automatically. exp and role (database role) keys are mandatory.

Authorizing Client Connection: You can pass in the JWT by following the instructions under the Realtime client lib. For example, refer to the Usage section in the @supabase/realtime-js client library.

Error Operational Codes

This is the list of operational codes that can help you understand your deployment and your usage.

Code	Description
RealtimeDisabledForConfiguration	The configuration provided to Realtime on connect will not be able to provide you any Postgres Changes
TenantNotFound	The tenant you are trying to connect to does not exist
ErrorConnectingToWebsocket	Error when trying to connect to the WebSocket server
ErrorAuthorizingWebsocket	Error when trying to authorize the WebSocket connection
TableHasSpacesInName	The table you are trying to listen to has spaces in its name which we are unable to support
UnableToDeleteTenant	Error when trying to delete a tenant
UnableToSetPolicies	Error when setting up Authorization Policies
UnableCheckoutConnection	Error when trying to checkout a connection from the tenant pool
UnableToSubscribeToPostgres	Error when trying to subscribe to Postgres changes
ChannelRateLimitReached	The number of channels you can create has reached its limit
ConnectionRateLimitReached	The number of connected clients as reached its limit
ClientJoinRateLimitReached	The rate of joins per second from your clients as reached the channel limits
UnableToConnectToTenantDatabase	Realtime was not able to connect to the tenant's database
RealtimeNodeDisconnected	Realtime is a distributed application and this means that one the system is unable to communicate with one of the distributed nodes
MigrationsFailedToRun	Error when running the migrations against the Tenant database that are required by Realtime
ErrorStartingPostgresCDCStream	Error when starting the Postgres CDC stream which is used for Postgres Changes
UnknownDataProcessed	An unknown data type was processed by the Realtime system
ErrorStartingPostgresCDC	Error when starting the Postgres CDC extension which is used for Postgres Changes
ReplicationSlotBeingUsed	The replication slot is being used by another transaction
PoolingReplicationPreparationError	Error when preparing the replication slot
PoolingReplicationError	Error when pooling the replication slot
SubscriptionDeletionFailed	Error when trying to delete a subscription for postgres changes
UnableToDeletePhantomSubscriptions	Error when trying to delete subscriptions that are no longer being used
UnableToCheckProcessesOnRemoteNode	Error when trying to check the processes on a remote node
UnableToCreateCounter	Error when trying to create a counter to track rate limits for a tenant
UnableToIncrementCounter	Error when trying to increment a counter to track rate limits for a tenant
UnableToDecrementCounter	Error when trying to decrement a counter to track rate limits for a tenant
UnableToUpdateCounter	Error when trying to update a counter to track rate limits for a tenant
UnableToFindCounter	Error when trying to find a counter to track rate limits for a tenant
UnhandledProcessMessage	Unhandled message received by a Realtime process
UnknownError	An unknown error occurred

License

This repo is licensed under Apache 2.0.

Credits

• Phoenix - Realtime server is built with the amazing Elixir framework.
• Phoenix Channels JavaScript Client - @supabase/realtime-js client library heavily draws from the Phoenix Channels client library.