Leptos Server Signals

Server signals are leptos signals kept in sync with the server through websockets.

The signals are read-only on the client side, and can be written to by the server. This is useful if you want real-time updates on the UI controlled by the server.

Changes to a signal are sent through a websocket to the client as json patches.

Feature flags

• ssr: ssr is enabled when rendering the app on the server.
• actix: integration with the Actix web framework.
• axum: integration with the Axum web framework.

Example

Cargo.toml

[dependencies]
leptos_server_signal = "*"
serde = { version = "*", features = ["derive"] }

[features]
ssr = [
  "leptos_server_signal/ssr",
  "leptos_server_signal/axum", # or actix
]

Client

use leptos::*;
use leptos_server_signal::create_server_signal;
use serde::{Deserialize, Serialize};

#[derive(Clone, Default, Serialize, Deserialize)]
pub struct Count {
    pub value: i32,
}

#[component]
pub fn App() -> impl IntoView {
    // Provide websocket connection
    leptos_server_signal::provide_websocket("ws://localhost:3000/ws").unwrap();

    // Create server signal
    let count = create_server_signal::<Count>("counter");

    view! {
        <h1>"Count: " {move || count.get().value.to_string()}</h1>
    }
}

Server (Axum)

#[cfg(feature = "ssr")]
pub async fn websocket(ws: WebSocketUpgrade) -> Response {
    ws.on_upgrade(handle_socket)
}

#[cfg(feature = "ssr")]
async fn handle_socket(mut socket: WebSocket) {
    let mut count = ServerSignal::<Count>::new("counter").unwrap();

    loop {
        tokio::time::sleep(Duration::from_millis(10)).await;
        let result = count.with(&mut socket, |count| count.value += 1).await;
        if result.is_err() {
            break;
        }
    }
}

Connection Retry

With the example above, the connection does not get reestablished after a connection lost. To regularly try to reconnect again, the function provide_websocket_with_retry(...) can be used:

#[component]
pub fn App() -> impl IntoView {
    // Provide websocket connection
    leptos_server_signal::provide_websocket_with_retry(
        "ws://localhost:3000/ws",
        5000, // retry in 5000 milliseconds
    ).unwrap();

    // ... code from above
}