Add beacon.watch (#3362)

> This is currently a WIP and all features are subject to alteration or removal at any time.

## Overview

The successor to #2873.

Contains the backbone of `beacon.watch` including syncing code, the initial API, and several core database tables.

See `watch/README.md` for more information, requirements and usage.

watch/src/server/mod.rs

@@ -0,0 +1,134 @@
+use crate::block_packing::block_packing_routes;
+use crate::block_rewards::block_rewards_routes;
+use crate::blockprint::blockprint_routes;
+use crate::config::Config as FullConfig;
+use crate::database::{self, PgPool};
+use crate::suboptimal_attestations::{attestation_routes, blockprint_attestation_routes};
+use axum::{
+    handler::Handler,
+    http::{StatusCode, Uri},
+    routing::get,
+    Extension, Json, Router,
+};
+use eth2::types::ErrorMessage;
+use log::info;
+use std::future::Future;
+use std::net::SocketAddr;
+use tokio::sync::oneshot;
+
+pub use config::Config;
+pub use error::Error;
+
+mod config;
+mod error;
+mod handler;
+
+pub async fn serve(config: FullConfig, shutdown: oneshot::Receiver<()>) -> Result<(), Error> {
+    let db = database::build_connection_pool(&config.database)?;
+    let (_, slots_per_epoch) = database::get_active_config(&mut database::get_connection(&db)?)?
+        .ok_or_else(|| {
+            Error::Other(
+                "Database not found. Please run the updater prior to starting the server"
+                    .to_string(),
+            )
+        })?;
+
+    let server = start_server(&config, slots_per_epoch as u64, db, async {
+        let _ = shutdown.await;
+    })?;
+
+    server.await?;
+
+    Ok(())
+}
+
+/// Creates a server that will serve requests using information from `config`.
+///
+/// The server will create its own connection pool to serve connections to the database.
+/// This is separate to the connection pool that is used for the `updater`.
+///
+/// The server will shut down gracefully when the `shutdown` future resolves.
+///
+/// ## Returns
+///
+/// This function will bind the server to the address specified in the config and then return a
+/// Future representing the actual server that will need to be awaited.
+///
+/// ## Errors
+///
+/// Returns an error if the server is unable to bind or there is another error during
+/// configuration.
+pub fn start_server(
+    config: &FullConfig,
+    slots_per_epoch: u64,
+    pool: PgPool,
+    shutdown: impl Future<Output = ()> + Send + Sync + 'static,
+) -> Result<impl Future<Output = Result<(), hyper::Error>> + 'static, Error> {
+    let mut routes = Router::new()
+        .route("/v1/slots", get(handler::get_slots_by_range))
+        .route("/v1/slots/:slot", get(handler::get_slot))
+        .route("/v1/slots/lowest", get(handler::get_slot_lowest))
+        .route("/v1/slots/highest", get(handler::get_slot_highest))
+        .route("/v1/slots/:slot/block", get(handler::get_block))
+        .route("/v1/blocks", get(handler::get_blocks_by_range))
+        .route("/v1/blocks/:block", get(handler::get_block))
+        .route("/v1/blocks/lowest", get(handler::get_block_lowest))
+        .route("/v1/blocks/highest", get(handler::get_block_highest))
+        .route(
+            "/v1/blocks/:block/previous",
+            get(handler::get_block_previous),
+        )
+        .route("/v1/blocks/:block/next", get(handler::get_block_next))
+        .route(
+            "/v1/blocks/:block/proposer",
+            get(handler::get_block_proposer),
+        )
+        .route("/v1/validators/:validator", get(handler::get_validator))
+        .route("/v1/validators/all", get(handler::get_all_validators))
+        .route(
+            "/v1/validators/:validator/latest_proposal",
+            get(handler::get_validator_latest_proposal),
+        )
+        .route("/v1/clients", get(handler::get_client_breakdown))
+        .route(
+            "/v1/clients/percentages",
+            get(handler::get_client_breakdown_percentages),
+        )
+        .merge(attestation_routes())
+        .merge(blockprint_routes())
+        .merge(block_packing_routes())
+        .merge(block_rewards_routes());
+
+    if config.blockprint.enabled && config.updater.attestations {
+        routes = routes.merge(blockprint_attestation_routes())
+    }
+
+    let app = routes
+        .fallback(route_not_found.into_service())
+        .layer(Extension(pool))
+        .layer(Extension(slots_per_epoch));
+
+    let addr = SocketAddr::new(config.server.listen_addr, config.server.listen_port);
+
+    let server = axum::Server::try_bind(&addr)?.serve(app.into_make_service());
+
+    let server = server.with_graceful_shutdown(async {
+        shutdown.await;
+    });
+
+    info!("HTTP server listening on {}", addr);
+
+    Ok(server)
+}
+
+// The default route indicating that no available routes matched the request.
+async fn route_not_found(uri: Uri) -> (StatusCode, Json<ErrorMessage>) {
+    (
+        StatusCode::METHOD_NOT_ALLOWED,
+        Json(ErrorMessage {
+            code: StatusCode::METHOD_NOT_ALLOWED.as_u16(),
+            message: format!("No route for {uri}"),
+            stacktraces: vec![],
+        }),
+    )
+}