Pubsub checks

src/robust_provider.rs

@@ -85,8 +85,8 @@ impl<N: Network> RobustProvider<N> {
 
     /// Set the base delay for exponential backoff retries.
     #[must_use]
-    pub fn min_delay(mut self, retry_interval: Duration) -> Self {
-        self.min_delay = retry_interval;
+    pub fn min_delay(mut self, min_delay: Duration) -> Self {
+        self.min_delay = min_delay;
         self
     }
 
@@ -105,8 +105,8 @@ impl<N: Network> RobustProvider<N> {
     ///
     /// Fallback providers are used when the primary provider times out or fails.
     #[must_use]
-    pub fn fallback(mut self, provider: RootProvider<N>) -> Self {
-        self.providers.push(provider);
+    pub fn fallback(mut self, provider: impl Provider<N>) -> Self {
+        self.providers.push(provider.root().to_owned());
         self
     }
 
@@ -122,9 +122,10 @@ impl<N: Network> RobustProvider<N> {
     ) -> Result<N::BlockResponse, Error> {
         info!("eth_getBlockByNumber called");
         let result = self
-            .retry_with_total_timeout(move |provider| async move {
-                provider.get_block_by_number(number).await
-            })
+            .retry_with_total_timeout(
+                move |provider| async move { provider.get_block_by_number(number).await },
+                false,
+            )
             .await;
         if let Err(e) = &result {
             error!(error = %e, "eth_getByBlockNumber failed");
@@ -144,6 +145,7 @@ impl<N: Network> RobustProvider<N> {
         let result = self
             .retry_with_total_timeout(
                 move |provider| async move { provider.get_block_number().await },
+                false,
             )
             .await;
         if let Err(e) = &result {
@@ -164,9 +166,10 @@ impl<N: Network> RobustProvider<N> {
     ) -> Result<N::BlockResponse, Error> {
         info!("eth_getBlockByHash called");
         let result = self
-            .retry_with_total_timeout(move |provider| async move {
-                provider.get_block_by_hash(hash).await
-            })
+            .retry_with_total_timeout(
+                move |provider| async move { provider.get_block_by_hash(hash).await },
+                false,
+            )
             .await;
         if let Err(e) = &result {
             error!(error = %e, "eth_getBlockByHash failed");
@@ -186,6 +189,7 @@ impl<N: Network> RobustProvider<N> {
         let result = self
             .retry_with_total_timeout(
                 move |provider| async move { provider.get_logs(filter).await },
+                false,
             )
             .await;
         if let Err(e) = &result {
@@ -202,11 +206,12 @@ impl<N: Network> RobustProvider<N> {
     /// after exhausting retries or if the call times out.
     pub async fn subscribe_blocks(&self) -> Result<Subscription<N::HeaderResponse>, Error> {
         info!("eth_subscribe called");
-        // We need this otherwise error is not clear
+        // immediately fail if primary does not support pubsub
         self.root().client().expect_pubsub_frontend();
         let result = self
             .retry_with_total_timeout(
                 move |provider| async move { provider.subscribe_blocks().await },
+                true,
             )
             .await;
         if let Err(e) = &result {
@@ -224,17 +229,27 @@ impl<N: Network> RobustProvider<N> {
     /// If the timeout is exceeded and fallback providers are available, it will
     /// attempt to use each fallback provider in sequence.
     ///
+    /// If `require_pubsub` is true, providers that don't support pubsub will be skipped.
+    ///
     /// # Errors
     ///
     /// - Returns [`RpcError<TransportErrorKind>`] with message "total operation timeout exceeded
     ///   and all fallback providers failed" if the overall timeout elapses and no fallback
     ///   providers succeed.
+    /// - Returns [`RpcError::Transport(TransportErrorKind::PubsubUnavailable)`] if `require_pubsub`
+    ///   is true and all providers don't support pubsub.
     /// - Propagates any [`RpcError<TransportErrorKind>`] from the underlying retries.
-    async fn retry_with_total_timeout<T: Debug, F, Fut>(&self, operation: F) -> Result<T, Error>
+    async fn retry_with_total_timeout<T: Debug, F, Fut>(
+        &self,
+        operation: F,
+        require_pubsub: bool,
+    ) -> Result<T, Error>
     where
         F: Fn(RootProvider<N>) -> Fut,
         Fut: Future<Output = Result<T, RpcError<TransportErrorKind>>>,
     {
+        let mut skipped_count = 0;
+
         let mut providers = self.providers.iter();
         let primary = providers.next().expect("should have primary provider");
 
@@ -253,6 +268,11 @@ impl<N: Network> RobustProvider<N> {
         // This loop starts at index 1 automatically
         for (idx, provider) in providers.enumerate() {
             let fallback_num = idx + 1;
+            if require_pubsub && !Self::supports_pubsub(provider) {
+                info!("Fallback provider {} doesn't support pubsub, skipping", fallback_num);
+                skipped_count += 1;
+                continue;
+            }
             info!("Attempting fallback provider {}/{}", fallback_num, self.providers.len() - 1);
 
             match self.try_provider_with_timeout(provider, &operation).await {
@@ -267,6 +287,13 @@ impl<N: Network> RobustProvider<N> {
             }
         }
 
+        // If all providers were skipped due to pubsub requirement
+        if skipped_count == self.providers.len() {
+            error!("All providers skipped - none support pubsub");
+            return Err(RpcError::Transport(TransportErrorKind::PubsubUnavailable).into());
+        }
+
+        // Return the last error encountered
         error!("All providers failed or timed out");
         Err(last_error)
     }
@@ -298,25 +325,30 @@ impl<N: Network> RobustProvider<N> {
         .map_err(Error::from)?
         .map_err(Error::from)
     }
+
+    /// Check if a provider supports pubsub
+    fn supports_pubsub(provider: &RootProvider<N>) -> bool {
+        provider.client().pubsub_frontend().is_some()
+    }
 }
 
 #[cfg(test)]
 mod tests {
     use super::*;
-    use alloy::network::Ethereum;
+    use alloy::{
+        network::Ethereum,
+        providers::{ProviderBuilder, WsConnect},
+    };
+    use alloy_node_bindings::Anvil;
     use std::sync::atomic::{AtomicUsize, Ordering};
     use tokio::time::sleep;
 
-    fn test_provider(
-        timeout: u64,
-        max_retries: usize,
-        retry_interval: u64,
-    ) -> RobustProvider<Ethereum> {
+    fn test_provider(timeout: u64, max_retries: usize, min_delay: u64) -> RobustProvider<Ethereum> {
         RobustProvider {
             providers: vec![RootProvider::new_http("http://localhost:8545".parse().unwrap())],
             max_timeout: Duration::from_millis(timeout),
             max_retries,
-            min_delay: Duration::from_millis(retry_interval),
+            min_delay: Duration::from_millis(min_delay),
         }
     }
 
@@ -327,11 +359,14 @@ mod tests {
         let call_count = AtomicUsize::new(0);
 
         let result = provider
-            .retry_with_total_timeout(|_| async {
-                call_count.fetch_add(1, Ordering::SeqCst);
-                let count = call_count.load(Ordering::SeqCst);
-                Ok(count)
-            })
+            .retry_with_total_timeout(
+                |_| async {
+                    call_count.fetch_add(1, Ordering::SeqCst);
+                    let count = call_count.load(Ordering::SeqCst);
+                    Ok(count)
+                },
+                false,
+            )
             .await;
 
         assert!(matches!(result, Ok(1)));
@@ -344,14 +379,17 @@ mod tests {
         let call_count = AtomicUsize::new(0);
 
         let result = provider
-            .retry_with_total_timeout(|_| async {
-                call_count.fetch_add(1, Ordering::SeqCst);
-                let count = call_count.load(Ordering::SeqCst);
-                match count {
-                    3 => Ok(count),
-                    _ => Err(TransportErrorKind::BackendGone.into()),
-                }
-            })
+            .retry_with_total_timeout(
+                |_| async {
+                    call_count.fetch_add(1, Ordering::SeqCst);
+                    let count = call_count.load(Ordering::SeqCst);
+                    match count {
+                        3 => Ok(count),
+                        _ => Err(TransportErrorKind::BackendGone.into()),
+                    }
+                },
+                false,
+            )
             .await;
 
         assert!(matches!(result, Ok(3)));
@@ -364,10 +402,13 @@ mod tests {
         let call_count = AtomicUsize::new(0);
 
         let result: Result<(), Error> = provider
-            .retry_with_total_timeout(|_| async {
-                call_count.fetch_add(1, Ordering::SeqCst);
-                Err(TransportErrorKind::BackendGone.into())
-            })
+            .retry_with_total_timeout(
+                |_| async {
+                    call_count.fetch_add(1, Ordering::SeqCst);
+                    Err(TransportErrorKind::BackendGone.into())
+                },
+                false,
+            )
             .await;
 
         assert!(matches!(result, Err(Error::RpcError(_))));
@@ -380,12 +421,98 @@ mod tests {
         let provider = test_provider(max_timeout, 10, 1);
 
         let result = provider
-            .retry_with_total_timeout(move |_provider| async move {
-                sleep(Duration::from_millis(max_timeout + 10)).await;
-                Ok(42)
-            })
+            .retry_with_total_timeout(
+                move |_provider| async move {
+                    sleep(Duration::from_millis(max_timeout + 10)).await;
+                    Ok(42)
+                },
+                false,
+            )
             .await;
 
         assert!(matches!(result, Err(Error::Timeout)));
     }
+
+    #[tokio::test]
+    async fn test_subscribe_fails_causes_backup_to_be_used() {
+        let anvil_1 = Anvil::new().port(2222_u16).try_spawn().expect("Failed to start anvil");
+
+        let ws_provider_1 = ProviderBuilder::new()
+            .connect_ws(WsConnect::new(anvil_1.ws_endpoint_url().as_str()))
+            .await
+            .expect("Failed to connect to WS");
+
+        let anvil_2 = Anvil::new().port(1111_u16).try_spawn().expect("Failed to start anvil");
+
+        let ws_provider_2 = ProviderBuilder::new()
+            .connect_ws(WsConnect::new(anvil_2.ws_endpoint_url().as_str()))
+            .await
+            .expect("Failed to connect to WS");
+
+        let robust = RobustProvider::new(ws_provider_1)
+            .fallback(ws_provider_2)
+            .max_timeout(Duration::from_secs(5))
+            .max_retries(10)
+            .min_delay(Duration::from_millis(100));
+
+        drop(anvil_1);
+
+        let result = robust.subscribe_blocks().await;
+
+        assert!(result.is_ok(), "Expected subscribe blocks to work");
+    }
+
+    #[tokio::test]
+    #[should_panic(expected = "called pubsub_frontend on a non-pubsub transport")]
+    async fn test_subscribe_fails_if_primary_provider_lacks_pubsub() {
+        let anvil = Anvil::new().try_spawn().expect("Failed to start anvil");
+
+        let http_provider = ProviderBuilder::new().connect_http(anvil.endpoint_url());
+        let ws_provider = ProviderBuilder::new()
+            .connect_ws(WsConnect::new(anvil.ws_endpoint_url().as_str()))
+            .await
+            .expect("Failed to connect to WS");
+
+        let robust = RobustProvider::new(http_provider)
+            .fallback(ws_provider)
+            .max_timeout(Duration::from_secs(5))
+            .max_retries(10)
+            .min_delay(Duration::from_millis(100));
+
+        let _ = robust.subscribe_blocks().await;
+    }
+
+    #[tokio::test]
+    async fn test_ws_fails_http_fallback_returns_primary_error() {
+        let anvil_1 = Anvil::new().try_spawn().expect("Failed to start anvil");
+
+        let ws_provider = ProviderBuilder::new()
+            .connect_ws(WsConnect::new(anvil_1.ws_endpoint_url().as_str()))
+            .await
+            .expect("Failed to connect to WS");
+
+        let anvil_2 = Anvil::new().port(8222_u16).try_spawn().expect("Failed to start anvil");
+        let http_provider = ProviderBuilder::new().connect_http(anvil_2.endpoint_url());
+
+        let robust = RobustProvider::new(ws_provider.clone())
+            .fallback(http_provider)
+            .max_timeout(Duration::from_millis(500))
+            .max_retries(0)
+            .min_delay(Duration::from_millis(10));
+
+        // force ws_provider to fail and return BackendGone
+        drop(anvil_1);
+
+        let err = robust.subscribe_blocks().await.unwrap_err();
+
+        // The error should be either a Timeout or BackendGone from the primary WS provider,
+        // NOT a PubsubUnavailable error (which would indicate HTTP fallback was attempted)
+        match err {
+            Error::Timeout => {}
+            Error::RpcError(e) => {
+                assert!(matches!(e.as_ref(), RpcError::Transport(TransportErrorKind::BackendGone)));
+            }
+            Error::BlockNotFound(id) => panic!("Unexpected error type: BlockNotFound({id})"),
+        }
+    }
 }

tests/block_range_scanner.rs

@@ -32,7 +32,7 @@ async fn live_mode_processes_all_blocks_respecting_block_confirmations() -> anyh
 
     robust_provider.root().anvil_mine(Some(1), None).await?;
 
-    assert_next!(stream, 6..=6);
+    assert_next!(stream, 6..=6, timeout = 10);
     assert_empty!(stream);
 
     // --- 1 block confirmation  ---
@@ -50,7 +50,7 @@ async fn live_mode_processes_all_blocks_respecting_block_confirmations() -> anyh
 
     robust_provider.root().anvil_mine(Some(1), None).await?;
 
-    assert_next!(stream, 11..=11);
+    assert_next!(stream, 11..=11, timeout = 10);
     assert_empty!(stream);
 
     Ok(())