chore(client): Update readme and rust example

README.md

@@ -108,6 +108,11 @@ It's possible to add limits for filters in config. If `filters` field is omitted
    - [Rust](examples/rust)
    - [TypeScript](examples/typescript)
 
+**NOTE**: Some load balancers will terminate gRPC connections if there are no messages sent from the client for a period of time.
+In order to mitigate this you need to send a message periodically. The `ping` field in the SubscribeRequest is used for this purpose.
+The gRPC server already sends pings to the client, so you can simply reply with a ping and your connection will remain open.
+You can see in the rust example how to reply to the ping from the server with the client.
+
 ### gRPC Tools
 
 #### Google Pub/Sub

examples/rust/src/bin/client.rs

@@ -524,7 +524,8 @@ async fn geyser_subscribe(
     request: SubscribeRequest,
     resub: usize,
 ) -> anyhow::Result<()> {
-    let (mut subscribe_tx, mut stream) = client.subscribe_with_request(Some(request)).await?;
+    let (mut subscribe_tx, mut stream) =
+        client.subscribe_with_request(Some(request.clone())).await?;
 
     info!("stream opened");
     let mut counter = 0;
@@ -549,6 +550,23 @@ async fn geyser_subscribe(
                         );
                         continue;
                     }
+                    Some(UpdateOneof::Ping(_)) => {
+                        // This is necessary to keep load balancers that expect client pings alive. If your load balancer doesn't
+                        // require periodic client pings then this is unnecessary
+                        subscribe_tx
+                            .send(SubscribeRequest {
+                                ping: Some(SubscribeRequestPing { id: 1 }),
+                                slots: request.slots.clone(),
+                                accounts: request.accounts.clone(),
+                                transactions: request.transactions.clone(),
+                                entry: request.entry.clone(),
+                                blocks: request.blocks.clone(),
+                                blocks_meta: request.blocks_meta.clone(),
+                                commitment: request.commitment.clone(),
+                                accounts_data_slice: request.accounts_data_slice.clone(),
+                            })
+                            .await?;
+                    }
                     _ => {}
                 }
                 info!("new message: {msg:?}")