status codes on health

TODO.md

@@ -30,7 +30,6 @@
   - even after removing a bunch of the locks, the deadlock still happens. i can't reliably reproduce. i just let it run for awhile and it happens.
   - running gdb shows the thread at tokio tungstenite thread is spinning near 100% cpu and none of the rest of the program is proceeding
   - fixed by https://github.com/gakonst/ethers-rs/pull/1287
-- [ ] quick requests/second timer until we have real stats
 - [ ] rpc errors propagate too far. one subscription failing ends the app. isolate the providers more
 - [ ] if web3 proxy gets an http error back, retry another node
 - [ ] endpoint for health checks. if no synced servers, give a 502 error

web3-proxy/src/connections.rs

@@ -315,6 +315,10 @@ impl Web3Connections {
         *self.synced_connections.load().get_head_block_hash()
     }
 
+    pub fn has_synced_rpcs(&self) -> bool {
+        self.synced_connections.load().inner.len() > 0
+    }
+
     /// Send the same request to all the handles. Returning the most common success or most common error.
     #[instrument(skip_all)]
     pub async fn try_send_parallel_requests(

web3-proxy/src/frontend/http.rs

@@ -11,6 +11,15 @@ pub async fn index() -> impl IntoResponse {
     "Hello, World!"
 }
 
+/// Health check page for load balancers to use
+pub async fn health(app: Extension<Arc<Web3ProxyApp>>) -> impl IntoResponse {
+    if app.get_balanced_rpcs().has_synced_rpcs() {
+        (StatusCode::OK, "OK")
+    } else {
+        (StatusCode::SERVICE_UNAVAILABLE, ":(")
+    }
+}
+
 /// Very basic status page
 pub async fn status(app: Extension<Arc<Web3ProxyApp>>) -> impl IntoResponse {
     // TODO: what else should we include? uptime? prometheus?

web3-proxy/src/frontend/mod.rs

@@ -21,8 +21,10 @@ pub async fn run(port: u16, proxy_app: Arc<Web3ProxyApp>) -> anyhow::Result<()>
         .route("/", post(http_proxy::proxy_web3_rpc))
         // `websocket /` goes to `proxy_web3_ws`
         .route("/", get(ws_proxy::websocket_handler))
-        // `GET /index.html` goes to `index` (todo, somehow combine this with http_proxy::proxy_web3_rpc)
+        // `GET /index.html` goes to `index`
         .route("/index.html", get(http::index))
+        // `GET /health` goes to `health`
+        .route("/health", get(http::health))
         // `GET /status` goes to `status`
         .route("/status", get(http::status))
         .layer(Extension(proxy_app));