bevy_stdb

A Bevy integration for SpacetimeDB.

Please enjoy this useless AI generated image based on the README contents of this repo.

Overview

bevy_stdb adapts SpacetimeDB's connection and callback model into Bevy-style resources, systems, plugins, and messages.

Features

• Builder-style setup via StdbPlugin
• Connection resource access through StdbConnection
• Table event bridging into normal Bevy Messages
• Managed subscription intent through StdbSubscriptions
• Optional reconnect support through StdbReconnectOptions

Example

use bevy::prelude::*;
use bevy_stdb::prelude::*;
use crate::module_bindings::{DbConnection, PlayerInfo, RemoteModule};

#[derive(Debug, Clone, Copy, Eq, PartialEq, Hash)]
pub enum MySubKey {
    PlayerInfo,
}

pub type StdbConn = StdbConnection<DbConnection>;
pub type StdbSubs = StdbSubscriptions<MySubKey, RemoteModule>;

fn main() {
    App::new()
        .add_plugins(DefaultPlugins)
        .add_plugins(
            StdbPlugin::<DbConnection, RemoteModule>::default()
                .with_database_name("my_module")
                .with_uri("http://localhost:3000")
                .add_table::<PlayerInfo>(|reg, db| reg.bind(db.player_info()))
                .with_subscriptions::<MySubKey>()
                .with_reconnect(StdbReconnectOptions::default())
                .with_background_driver(DbConnection::run_threaded),
        )
        .add_systems(Startup, connect)
        .add_systems(Update, (subscribe_on_connect, on_player_info_insert))
        .run();
}

fn connect(mut cmds: StdbCmds) {
    cmds.connect(StdbConnectOptions::default());
}

fn subscribe_on_connect(
    mut connected: ReadStdbConnectedMessage,
    mut subs: ResMut<StdbSubs>,
) {
    if connected.read().next().is_some() {
        subs.subscribe_query(MySubKey::PlayerInfo, |q| q.from.player_info());
    }
}

fn on_player_info_insert(mut msgs: ReadInsertMessage<PlayerInfo>) {
    for msg in msgs.read() {
        info!("player inserted: {:?}", msg.row);
    }
}

Connection driving

bevy_stdb supports two connection-driving modes:

• with_background_driver(...): start SpacetimeDB's background processing for the active connection
• with_frame_driver(...): drive SpacetimeDB from the Bevy schedule each frame

Exactly one driver must be configured. These modes are mutually exclusive, and in most applications you'll want with_background_driver(...).

If WASM support is needed, you can enable the browser feature flag in both this crate and your spacetimedb-sdk crate using a target cfg:

# Enable browser support for wasm builds.
# Replace `*` with the versions you are using.
[target.wasm32-unknown-unknown.dependencies]
spacetimedb-sdk = { version = "*", features = ["browser"] }
bevy_stdb = { version = "*", features = ["browser"] }

I recommend checking out the bevy_cli 2d template for a good starter example using WASM + native with nice Bevy features configured.

Native background driving

On native targets, the typical choice is run_threaded:

fn main() {
    let stdb_plugin = StdbPlugin::<DbConnection, RemoteModule>::default()
        .with_database_name("my_module")
        .with_uri("http://localhost:3000")
        .with_background_driver(DbConnection::run_threaded);
}

Browser / wasm background driving (async)

On browser targets, use the generated background task helper instead:

fn main() {
    let stdb_plugin = StdbPlugin::<DbConnection, RemoteModule>::default()
        .with_database_name("my_module")
        .with_uri("http://localhost:3000")
        .with_background_driver(DbConnection::run_background_task)
}

If you target both native and browser, I recommend selecting the background driver with cfg:

fn main() {
    let mut stdb_plugin = StdbPlugin::<DbConnection, RemoteModule>::default()
        .with_database_name("my_module")
        .with_uri("http://localhost:3000");

    #[cfg(target_arch = "wasm32")]
    let driver = DbConnection::run_background_task;
    #[cfg(not(target_arch = "wasm32"))]
    let driver = DbConnection::run_threaded;
    
    stdb_plugin = stdb_plugin.with_background_driver(driver);
}

Bevy frame-tick driving

Use frame_tick when you want Bevy to drive connection progress from Bevy each frame. Internally, bevy_stdb runs this driver from PreUpdate:

use bevy::prelude::*;
use bevy_stdb::prelude::*;
use crate::module_bindings::{DbConnection, RemoteModule};

fn main() {
    let stdb_plugin = StdbPlugin::<DbConnection, RemoteModule>::default()
        .with_database_name("my_module")
        .with_uri("http://localhost:3000")
        .with_frame_driver(DbConnection::frame_tick);
}

Table registration

Use the StdbPlugin builder methods to register table bindings during app setup.

Each method eagerly registers the Bevy message channels for the row type you specify and stores a deferred binding callback that runs whenever a connection becomes active.

.add_table::<PlayerInfo>(|reg, db| reg.bind(db.player_info()))
.add_table_without_pk::<WorldClock>(|reg, db| reg.bind(db.world_clock()))
.add_event_table::<DamageEvent>(|reg, db| reg.bind(db.damage_events()))
.add_view::<NearbyMonster>(|reg, db| reg.bind(db.nearby_monsters()))

Table message registration happens eagerly at startup; callback binding is deferred until a connection is active.

Messages

Depending on the table shape, bevy_stdb forwards updates into Bevy messages such as:

• InsertMessage<T>
• DeleteMessage<T>
• UpdateMessage<T>
• InsertUpdateMessage<T>

This lets normal Bevy systems react to database changes using message readers. These messages include both the affected row data and the SpacetimeDB event that triggered the change.

use crate::module_bindings::Reducer;
use bevy_stdb::prelude::*;
use spacetimedb_sdk::Event;

fn on_person_insert(mut messages: ReadInsertMessage<PersonRow>) {
  for msg in messages.read() {
    match &msg.event {
      Event::Reducer(r) => {
        /* r.status, r.timestamp, r.reducer */ 
        if let Reducer::CreatePerson(p) = &r.reducer { /* ... */ }
      },
      _ => { /* ... */ }
    }
  }
}

Subscriptions

StdbSubscriptions stores desired subscription intent separately from the live connection. Subscriptions are keyed by a type you define, so you can refer to them by domain-specific identifiers for dynamic resubscription or unsubscription.

Enable it during plugin setup with with_subscriptions, then queue subscriptions from any Bevy system — typically in response to StdbConnectedMessage. Queued intent is automatically re-applied after a reconnect.

There are two ways to subscribe:

• subscribe_sql(key, "SELECT * FROM my_table") — raw SQL string
• subscribe_query(key, |q| q.from.my_table()) — generated query builder

ReadStdbSubscriptionAppliedMessage and ReadStdbSubscriptionErrorMessage are emitted for the on_applied and on_error callbacks per subscription.

fn on_applied(mut applied_msgs: ReadStdbSubscriptionAppliedMessage<SubKey>, conn: Res<StdbConn>) {
  for msg in applied_msgs.read() {
    if msg.is(&SubKey::MyCharacters) {
      println!("You have {} characters.", conn.db().my_characters().count());
    }
  }
}

Reconnects

Reconnect behavior is opt-in. Pass StdbReconnectOptions to StdbPlugin::with_reconnect to enable it.

The reconnect cycle activates when a disconnect message includes an error, or when a connection attempt fails — including a first-time failure. A clean disconnect() call does not trigger a retry. While a connection attempt is in-flight the timer is paused; it re-arms once the attempt resolves. The cycle resets fully on a successful connect so the full attempt budget is available again.

.with_reconnect(StdbReconnectOptions {
    initial_delay: Duration::from_secs(1), // delay before the first retry
    backoff_factor: 1.5,                   // multiplier applied after each failure
    max_delay: Duration::from_secs(15),    // delay is capped at this value
    max_attempts: 0,                       // 0 = retry indefinitely
})

When a reconnect succeeds:

• the StdbConnection resource is replaced
• table callbacks are re-bound
• subscriptions are re-applied

Type Aliases

It is useful to define some type aliases of your own. I suggest making aliases for the connection, subscription, and commands:

#[derive(Clone, Eq, Hash, PartialEq, Debug)]
pub enum SubKeys {
    PlayerInfo,
    TimeOfDay,
}

pub type StdbConn = StdbConnection<DbConnection>;
pub type StdbSubs = StdbSubscriptions<SubKeys, RemoteModule>;
pub type StdbCmds<'w, 's> = StdbCommands<'w, 's, DbConnection, RemoteModule>;

fn example_system(conn: Res<StdbConn>, mut subs: ResMut<StdbSubs>) {
    let my_table = conn.db().player_info().id().find(&1);
    subs.subscribe_query(SubKeys::TimeOfDay, |q| q.from.world_clock());
}

Using commands

Use StdbCommands<C, M> to connect or disconnect at runtime, optionally overriding the token, URI, or module name configured on the plugin.

pub type StdbCmds<'w, 's> = StdbCommands<'w, 's, DbConnection, RemoteModule>;

// Connect with plugin defaults:
fn connect(mut cmds: StdbCmds) {
    cmds.connect(StdbConnectOptions::default());
}

// Connect with a runtime token override:
fn connect_with_token(mut cmds: StdbCmds) {
    cmds.connect(StdbConnectOptions::from_token("json.web.token"));
}

See StdbConnectOptions for all available overrides (from_token, from_uri, from_database_name, from_target).

Connection-dependent resources

bevy_stdb resources are only available while a connection is active. Guard systems with resource_exists::<StdbConnection<_>>() or accept the connection as an optional parameter. If you need to detect that a connection has been lost before the resource is cleaned up, StdbConnection::is_active() checks whether the underlying send channel is still open:

use bevy::prelude::*;
use bevy_stdb::prelude::*;
use crate::module_bindings::{DbConnection, RemoteModule};

pub type StdbConn = StdbConnection<DbConnection>;

fn main() {
    App::new()
        .add_plugins(DefaultPlugins)
        .add_plugins(
            StdbPlugin::<DbConnection, RemoteModule>::default()
                .with_database_name("my_module")
                .with_uri("http://localhost:3000")
                .with_background_driver(DbConnection::run_threaded),
        )
        .add_systems(
            Update,
            my_system_active.run_if(|conn: Option<Res<StdbConn>>| conn.is_some_and(|c| c.is_active()))
        )
        .add_systems(Update, my_system_option_res)
        .run();
}

fn my_system_active(conn: Res<StdbConn>) {
    // Only runs when StdbConnection resource exists
}

fn my_system_option_res(conn: Option<Res<StdbConn>>) {
    if let Some(conn) = conn {
        // Safe to access connection
    }
}

Compatibility

Notes

This crate focuses on table-driven client workflows. Reducer and procedure access still exist through the active StdbConnection, but the primary Bevy-facing event flow is table/message based.

Special thanks to bevy_spacetimedb for the inspiration!