Adding an opinionated way to integrate Prometheus into a Jsonrpsee backend #1334

Eikix · 2024-03-27T15:56:17Z

Eikix
Mar 27, 2024

After #1328, I'm asking here if there should be an opinionated way to add metrics to Jsonrpsee.

We currently have this piece of code in Kakarot kkrt-labs/kakarot-rpc#874 ->

/// # Errors
///
/// Will return `Err` if an error occurs when running the `ServerBuilder` start fails.
pub async fn run_server(
    kakarot_rpc_module: RpcModule<()>,
    rpc_config: RPCConfig,
) -> Result<(SocketAddr, ServerHandle), RpcError> {
    let RPCConfig { socket_addr } = rpc_config;

    let cors = CorsLayer::new().allow_methods(Any).allow_origin(Any).allow_headers(Any);

    let http_middleware =
        tower::ServiceBuilder::new().layer(ProxyGetRequestLayer::new("/health", "net_health")?).layer(cors);

    // Creating the prometheus registry to register the metrics
    let registry = Registry::new();
    // register the metrics
    let metrics = RpcMetrics::new(Some(&registry))?.map(|m| MetricsLayer::new(m, "http"));
    tokio::spawn(async move {
        // serve the prometheus metrics on the given port so that it can be read
        let _ = init_prometheus(
            SocketAddr::new(
                std::net::IpAddr::V4(Ipv4Addr::new(0, 0, 0, 0)),
                get_env_or_default("PROMETHEUS_PORT", "9615").parse().unwrap(),
            ),
            registry,
        )
        .await;
    });
    // add the metrics as a middleware to the RPC so that every new RPC call fires prometheus metrics
    // upon start, finish etc. we don't need to manually handle each method, it should automatically
    // work for any new method.
    let rpc_middleware = RpcServiceBuilder::new().option_layer(metrics);

    let server = ServerBuilder::default()
        .max_connections(get_env_or_default("RPC_MAX_CONNECTIONS", "100").parse().unwrap())
        .set_http_middleware(http_middleware)
        .set_rpc_middleware(rpc_middleware)
        .build(socket_addr.parse::<SocketAddr>()?)
        .await?;

    let addr = server.local_addr()?;
    let handle = server.start(kakarot_rpc_module);

    Ok((addr, handle))
}

And:

/// Initializes the metrics context, and starts an HTTP server
/// to serve metrics.
pub async fn init_prometheus(prometheus_addr: SocketAddr, registry: Registry) -> Result<(), Error> {
    let listener =
        tokio::net::TcpListener::bind(&prometheus_addr).await.map_err(|_| Error::PortInUse(prometheus_addr))?;

    init_prometheus_with_listener(listener, registry).await
}

/// Init prometheus using the given listener.
async fn init_prometheus_with_listener(listener: tokio::net::TcpListener, registry: Registry) -> Result<(), Error> {
    let listener = hyper::server::conn::AddrIncoming::from_listener(listener)?;
    log::info!("〽️ Prometheus exporter started at {}", listener.local_addr());

    let service = make_service_fn(move |_| {
        let registry = registry.clone();

        async move { Ok::<_, hyper::Error>(service_fn(move |req: Request<Body>| request_metrics(req, registry.clone()))) }
    });

    let (signal, on_exit) = tokio::sync::oneshot::channel::<()>();
    let server = Server::builder(listener).serve(service).with_graceful_shutdown(async {
        let _ = on_exit.await;
    });

    let result = server.await.map_err(Into::into);

    // Gracefully shutdown server, otherwise the server does not stop if it has open connections
    let _ = signal.send(());

    result
}

Which relies on code from Substrate:

I'll probably open a PR to add an example to the examples folder but before, I think it'd be nice to add metrics to a JsonRpsee server in a smoother way. Maybe there exists one already

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Adding an opinionated way to integrate Prometheus into a Jsonrpsee backend #1334

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Adding an opinionated way to integrate Prometheus into a Jsonrpsee backend #1334

Eikix Mar 27, 2024

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Eikix
Mar 27, 2024