handle empty futures

TODO.md

@@ -743,7 +743,7 @@ in another repo: event subscriber
 - [ ] have an upgrade tier that queries multiple backends at once. returns on first Ok result, collects errors. if no Ok, find the most common error and then respond with that
 - [ ] give public_recent_ips_salt a better, more general, name
 - [ ] include tier in the head block logs?
-- [ ] i think i use FuturesUnordered when a try_join_all might be better
+- [x] i think i use FuturesUnordered when a try_join_all might be better
 - [ ] since we are read-heavy on our configs, maybe we should use a cache
   - "using a thread local storage and explicit types" https://docs.rs/arc-swap/latest/arc_swap/cache/struct.Cache.html
 - [ ] tests for config reloading

web3_proxy/src/rpcs/one.rs

@@ -853,11 +853,23 @@ impl Web3Rpc {
             }
         }
 
+        if futures.is_empty() {
+            // we didn't have anything to subscribe to. what should happen?
+            let clone = self.clone();
+
+            loop {
+                sleep(Duration::from_secs(60)).await;
+                if self.should_disconnect() {
+                    break;
+                }
+            }
+        } else {
             // exit if any of the futures exit
             // TODO: have an enum for which one exited?
             let (first_exit, _, _) = select_all(futures).await;
 
             debug!(?first_exit, "subscriptions on {} exited", self);
+        }
 
         // clear the head block
         if let Some(block_and_rpc_sender) = block_and_rpc_sender {