use watch instead of arcswap

Cargo.lock

@@ -105,12 +105,6 @@ dependencies = [
  "backtrace",
 ]
 
-[[package]]
-name = "arc-swap"
-version = "1.6.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "bddcadddf5e9015d310179a59bb28c4d4b9920ad0f11e8e14dbadf654890c9a6"
-
 [[package]]
 name = "argh"
 version = "0.1.10"
@@ -5574,7 +5568,6 @@ name = "web3_proxy"
 version = "0.13.0"
 dependencies = [
  "anyhow",
- "arc-swap",
  "argh",
  "axum",
  "axum-client-ip",

web3_proxy/Cargo.toml

@@ -20,7 +20,6 @@ redis-rate-limiter = { path = "../redis-rate-limiter" }
 thread-fast-rng = { path = "../thread-fast-rng" }
 
 anyhow = { version = "1.0.68", features = ["backtrace"] }
-arc-swap = "1.6.0"
 argh = "0.1.10"
 axum = { version = "0.6.3", features = ["headers", "ws"] }
 axum-client-ip = "0.3.1"

web3_proxy/src/app/mod.rs

@@ -188,7 +188,7 @@ pub struct Web3ProxyApp {
     response_cache: ResponseCache,
     // don't drop this or the sender will stop working
     // TODO: broadcast channel instead?
-    head_block_receiver: watch::Receiver<ArcBlock>,
+    watch_consensus_head_receiver: watch::Receiver<ArcBlock>,
     pending_tx_sender: broadcast::Sender<TxStatus>,
     pub config: AppConfig,
     pub db_conn: Option<sea_orm::DatabaseConnection>,
@@ -533,7 +533,8 @@ impl Web3ProxyApp {
         };
 
         // TODO: i don't like doing Block::default here! Change this to "None"?
-        let (head_block_sender, head_block_receiver) = watch::channel(Arc::new(Block::default()));
+        let (watch_consensus_head_sender, watch_consensus_head_receiver) =
+            watch::channel(Arc::new(Block::default()));
         // TODO: will one receiver lagging be okay? how big should this be?
         let (pending_tx_sender, pending_tx_receiver) = broadcast::channel(256);
 
@@ -570,7 +571,7 @@ impl Web3ProxyApp {
             http_client.clone(),
             vredis_pool.clone(),
             block_map.clone(),
-            Some(head_block_sender),
+            Some(watch_consensus_head_sender),
             top_config.app.min_sum_soft_limit,
             top_config.app.min_synced_rpcs,
             Some(pending_tx_sender.clone()),
@@ -598,6 +599,8 @@ impl Web3ProxyApp {
                 vredis_pool.clone(),
                 block_map,
                 // subscribing to new heads here won't work well. if they are fast, they might be ahead of balanced_rpcs
+                // they also often have low rate limits
+                // however, they are well connected to miners/validators. so maybe using them as a safety check would be good
                 None,
                 0,
                 0,
@@ -706,7 +709,7 @@ impl Web3ProxyApp {
             balanced_rpcs,
             private_rpcs,
             response_cache,
-            head_block_receiver,
+            watch_consensus_head_receiver,
             pending_tx_sender,
             pending_transactions,
             frontend_ip_rate_limiter,
@@ -730,7 +733,7 @@ impl Web3ProxyApp {
     }
 
     pub fn head_block_receiver(&self) -> watch::Receiver<ArcBlock> {
-        self.head_block_receiver.clone()
+        self.watch_consensus_head_receiver.clone()
     }
 
     pub async fn prometheus_metrics(&self) -> String {
@@ -1362,10 +1365,10 @@ impl Web3ProxyApp {
             method => {
                 // emit stats
 
-                // TODO: if no servers synced, wait for them to be synced?
+                // TODO: if no servers synced, wait for them to be synced? probably better to error and let haproxy retry another server
-                let head_block = self
+                let head_block_num = self
                     .balanced_rpcs
-                    .head_block()
+                    .head_block_num()
                     .context("no servers synced")?;
 
                 // we do this check before checking caches because it might modify the request params
@@ -1375,7 +1378,7 @@ impl Web3ProxyApp {
                     authorization,
                     method,
                     request.params.as_mut(),
-                    head_block.number(),
+                    head_block_num,
                     &self.balanced_rpcs,
                 )
                 .await?

web3_proxy/src/app/ws.rs

@@ -50,7 +50,7 @@ impl Web3ProxyApp {
         match request_json.params.as_ref() {
             Some(x) if x == &json!(["newHeads"]) => {
                 let authorization = authorization.clone();
-                let head_block_receiver = self.head_block_receiver.clone();
+                let head_block_receiver = self.watch_consensus_head_receiver.clone();
                 let stat_sender = self.stat_sender.clone();
 
                 trace!("newHeads subscription {:?}", subscription_id);

web3_proxy/src/rpcs/blockchain.rs

@@ -165,9 +165,15 @@ impl Web3Connections {
                 let request: JsonRpcRequest = serde_json::from_value(request)?;
 
                 // TODO: request_metadata? maybe we should put it in the authorization?
-                // TODO: don't hard code allowed lag
+                // TODO: think more about this wait_for_sync
                 let response = self
-                    .try_send_best_consensus_head_connection(authorization, request, None, None)
+                    .try_send_best_consensus_head_connection(
+                        authorization,
+                        request,
+                        None,
+                        None,
+                        true,
+                    )
                     .await?;
 
                 let block = response.result.context("failed fetching block")?;
@@ -199,6 +205,7 @@ impl Web3Connections {
     }
 
     /// Get the heaviest chain's block from cache or backend rpc
+    /// Caution! If a future block is requested, this might wait forever. Be sure to have a timeout outside of this!
     pub async fn cannonical_block(
         &self,
         authorization: &Arc<Authorization>,
@@ -208,23 +215,33 @@ impl Web3Connections {
         // maybe save them during save_block in a blocks_by_number Cache<U64, Vec<ArcBlock>>
         // if theres multiple, use petgraph to find the one on the main chain (and remove the others if they have enough confirmations)
 
+        let mut consensus_head_receiver = self
+            .watch_consensus_head_receiver
+            .as_ref()
+            .context("need new head subscriptions to fetch cannonical_block")?
+            .clone();
+
         // be sure the requested block num exists
-        let head_block_num = self.head_block_num().context("no servers in sync")?;
+        let mut head_block_num = consensus_head_receiver.borrow_and_update().number;
+
+        loop {
+            if let Some(head_block_num) = head_block_num {
+                if num <= &head_block_num {
+                    break;
+                }
+            }
+
+            consensus_head_receiver.changed().await?;
+
+            head_block_num = consensus_head_receiver.borrow_and_update().number;
+        }
+
+        let head_block_num =
+            head_block_num.expect("we should only get here if we have a head block");
 
         // TODO: geth does 64, erigon does 90k. sometimes we run a mix
         let archive_needed = num < &(head_block_num - U64::from(64));
 
-        if num > &head_block_num {
-            // TODO: i'm seeing this a lot when using ethspam. i dont know why though. i thought we delayed publishing
-            // TODO: instead of error, maybe just sleep and try again?
-            // TODO: this should be a 401, not a 500
-            return Err(anyhow::anyhow!(
-                "Head block is #{}, but #{} was requested",
-                head_block_num,
-                num
-            ));
-        }
-
         // try to get the hash from our cache
         // deref to not keep the lock open
         if let Some(block_hash) = self.block_numbers.get(num) {
@@ -243,7 +260,7 @@ impl Web3Connections {
         // TODO: if error, retry?
         // TODO: request_metadata or authorization?
         let response = self
-            .try_send_best_consensus_head_connection(authorization, request, None, Some(num))
+            .try_send_best_consensus_head_connection(authorization, request, None, Some(num), true)
             .await?;
 
         let raw_block = response.result.context("no block result")?;
@@ -320,6 +337,8 @@ impl Web3Connections {
             .best_consensus_connections(authorization, self)
             .await;
 
+        // TODO: what should we do if the block number of new_synced_connections is < old_synced_connections? wait?
+
         let includes_backups = new_synced_connections.includes_backups;
         let consensus_head_block = new_synced_connections.head_block.clone();
         let num_consensus_rpcs = new_synced_connections.num_conns();
@@ -327,14 +346,14 @@ impl Web3Connections {
         let num_active_rpcs = consensus_finder.all.rpc_name_to_hash.len();
         let total_rpcs = self.conns.len();
 
-        let old_synced_connections = self
+        let old_consensus_head_connections = self
-            .synced_connections
+            .watch_consensus_connections_sender
-            .swap(Arc::new(new_synced_connections));
+            .send_replace(Arc::new(new_synced_connections));
 
         let includes_backups_str = if includes_backups { "B " } else { "" };
 
         if let Some(consensus_saved_block) = consensus_head_block {
-            match &old_synced_connections.head_block {
+            match &old_consensus_head_connections.head_block {
                 None => {
                     debug!(
                         "first {}{}/{}/{}/{} block={}, rpc={}",
@@ -843,7 +862,13 @@ impl ConsensusFinder {
             Some(x) => x.number.expect("blocks here should always have a number"),
         };
 
-        let min_block_num = highest_block_num.saturating_sub(U64::from(5));
+        // TODO: also needs to be not less than our current head
+        let mut min_block_num = highest_block_num.saturating_sub(U64::from(5));
+
+        // we also want to be sure we don't ever go backwards!
+        if let Some(current_consensus_head_num) = web3_connections.head_block_num() {
+            min_block_num = min_block_num.max(current_consensus_head_num);
+        }
 
         // TODO: pass `min_block_num` to consensus_head_connections?
         let consensus_head_for_main = self

web3_proxy/src/rpcs/connections.rs

@@ -11,7 +11,6 @@ use crate::frontend::authorization::{Authorization, RequestMetadata};
 use crate::frontend::rpc_proxy_ws::ProxyMode;
 use crate::jsonrpc::{JsonRpcForwardedResponse, JsonRpcRequest};
 use crate::rpcs::transactions::TxStatus;
-use arc_swap::ArcSwap;
 use counter::Counter;
 use derive_more::From;
 use ethers::prelude::{ProviderError, TxHash, H256, U64};
@@ -38,9 +37,12 @@ use tokio::time::{interval, sleep, sleep_until, Duration, Instant, MissedTickBeh
 /// A collection of web3 connections. Sends requests either the current best server or all servers.
 #[derive(From)]
 pub struct Web3Connections {
-    pub(crate) conns: HashMap<String, Arc<Web3Connection>>,
     /// any requests will be forwarded to one (or more) of these connections
-    pub(super) synced_connections: ArcSwap<ConsensusConnections>,
+    pub(crate) conns: HashMap<String, Arc<Web3Connection>>,
+    /// all providers with the same consensus head block. won't update if there is no `self.watch_consensus_head_sender`
+    pub(super) watch_consensus_connections_sender: watch::Sender<Arc<ConsensusConnections>>,
+    /// this head receiver makes it easy to wait until there is a new block
+    pub(super) watch_consensus_head_receiver: Option<watch::Receiver<ArcBlock>>,
     pub(super) pending_transactions:
         Cache<TxHash, TxStatus, hashbrown::hash_map::DefaultHashBuilder>,
     /// TODO: this map is going to grow forever unless we do some sort of pruning. maybe store pruned in redis?
@@ -62,7 +64,7 @@ impl Web3Connections {
         http_client: Option<reqwest::Client>,
         redis_pool: Option<redis_rate_limiter::RedisPool>,
         block_map: BlockHashesCache,
-        head_block_sender: Option<watch::Sender<ArcBlock>>,
+        watch_consensus_head_sender: Option<watch::Sender<ArcBlock>>,
         min_sum_soft_limit: u32,
         min_head_rpcs: usize,
         pending_tx_sender: Option<broadcast::Sender<TxStatus>>,
@@ -138,7 +140,7 @@ impl Web3Connections {
                 let redis_pool = redis_pool.clone();
                 let http_interval_sender = http_interval_sender.clone();
 
-                let block_sender = if head_block_sender.is_some() {
+                let block_sender = if watch_consensus_head_sender.is_some() {
                     Some(block_sender.clone())
                 } else {
                     None
@@ -192,8 +194,6 @@ impl Web3Connections {
             }
         }
 
-        let synced_connections = ConsensusConnections::default();
-
         // TODO: max_capacity and time_to_idle from config
         // all block hashes are the same size, so no need for weigher
         let block_hashes = Cache::builder()
@@ -206,9 +206,15 @@ impl Web3Connections {
             .max_capacity(10_000)
             .build_with_hasher(hashbrown::hash_map::DefaultHashBuilder::default());
 
+        let (watch_consensus_connections_sender, _) = watch::channel(Default::default());
+
+        let watch_consensus_head_receiver =
+            watch_consensus_head_sender.as_ref().map(|x| x.subscribe());
+
         let connections = Arc::new(Self {
             conns: connections,
-            synced_connections: ArcSwap::new(Arc::new(synced_connections)),
+            watch_consensus_connections_sender,
+            watch_consensus_head_receiver,
             pending_transactions,
             block_hashes,
             block_numbers,
@@ -228,7 +234,7 @@ impl Web3Connections {
                         authorization,
                         pending_tx_id_receiver,
                         block_receiver,
-                        head_block_sender,
+                        watch_consensus_head_sender,
                         pending_tx_sender,
                     )
                     .await
@@ -447,11 +453,12 @@ impl Web3Connections {
             (Option<U64>, u64),
             Vec<Arc<Web3Connection>>,
         > = {
-            let synced_connections = self.synced_connections.load();
+            let synced_connections = self.watch_consensus_connections_sender.borrow().clone();
 
             let head_block_num = if let Some(head_block) = synced_connections.head_block.as_ref() {
                 head_block.number()
             } else {
+                // TODO: optionally wait for a head block >= min_block_needed
                 return Ok(OpenRequestResult::NotReady);
             };
 
@@ -495,6 +502,7 @@ impl Web3Connections {
                     }
                 }
                 cmp::Ordering::Greater => {
+                    // TODO? if the blocks is close and wait_for_sync and allow_backups, wait for change on a watch_consensus_connections_receiver().subscribe()
                     return Ok(OpenRequestResult::NotReady);
                 }
             }
@@ -712,18 +720,27 @@ impl Web3Connections {
     }
 
     /// be sure there is a timeout on this or it might loop forever
+    /// TODO: think more about wait_for_sync
     pub async fn try_send_best_consensus_head_connection(
         &self,
         authorization: &Arc<Authorization>,
         request: JsonRpcRequest,
         request_metadata: Option<&Arc<RequestMetadata>>,
         min_block_needed: Option<&U64>,
+        wait_for_sync: bool,
     ) -> anyhow::Result<JsonRpcForwardedResponse> {
         let mut skip_rpcs = vec![];
 
+        let mut watch_consensus_connections = if wait_for_sync {
+            Some(self.watch_consensus_connections_sender.subscribe())
+        } else {
+            None
+        };
+
         // TODO: maximum retries? right now its the total number of servers
         loop {
             // TODO: is self.conns still right now that we split main and backup servers?
+            // TODO: if a new block arrives, we probably want to reset the skip list
             if skip_rpcs.len() == self.conns.len() {
                 // no servers to try
                 break;
@@ -833,9 +850,6 @@ impl Web3Connections {
                                 rpc, err
                             );
 
-                            // TODO: sleep how long? until synced_connections changes or rate limits are available
-                            // sleep(Duration::from_millis(100)).await;
-
                             continue;
                         }
                     }
@@ -851,16 +865,38 @@ impl Web3Connections {
                         request_metadata.no_servers.fetch_add(1, Ordering::Release);
                     }
 
-                    sleep_until(retry_at).await;
+                    if let Some(watch_consensus_connections) = watch_consensus_connections.as_mut()
-
+                    {
-                    continue;
+                        // TODO: if there are other servers in synced_connections, we should continue now
+                        // wait until retry_at OR synced_connections changes
+                        tokio::select! {
+                            _ = sleep_until(retry_at) => {
+                                skip_rpcs.pop();
+                            }
+                            _ = watch_consensus_connections.changed() => {
+                                // TODO: would be nice to save this retry_at so we don't keep hitting limits
+                                let _ = watch_consensus_connections.borrow_and_update();
+                            }
+                        }
+                        continue;
+                    } else {
+                        break;
+                    }
                 }
                 OpenRequestResult::NotReady => {
                     if let Some(request_metadata) = request_metadata {
                         request_metadata.no_servers.fetch_add(1, Ordering::Release);
                     }
 
-                    break;
+                    if wait_for_sync {
+                        // TODO: race here. there might have been a change while we were waiting on the previous server
+                        self.watch_consensus_connections_sender
+                            .subscribe()
+                            .changed()
+                            .await?;
+                    } else {
+                        break;
+                    }
                 }
             }
         }
@@ -979,6 +1015,7 @@ impl Web3Connections {
                     request,
                     request_metadata,
                     min_block_needed,
+                    true,
                 )
                 .await
             }
@@ -1007,8 +1044,11 @@ impl Serialize for Web3Connections {
         let conns: Vec<&Web3Connection> = self.conns.values().map(|x| x.as_ref()).collect();
         state.serialize_field("conns", &conns)?;
 
-        let synced_connections = &**self.synced_connections.load();
+        {
-        state.serialize_field("synced_connections", synced_connections)?;
+            let consensus_connections = self.watch_consensus_connections_sender.borrow().clone();
+            // TODO: rename synced_connections to consensus_connections?
+            state.serialize_field("synced_connections", &consensus_connections)?;
+        }
 
         self.block_hashes.sync();
         self.block_numbers.sync();
@@ -1128,9 +1168,13 @@ mod tests {
             (lagged_rpc.name.clone(), lagged_rpc.clone()),
         ]);
 
+        let (watch_consensus_connections_sender, _) = watch::channel(Default::default());
+
+        // TODO: make a Web3Connections::new
         let conns = Web3Connections {
             conns,
-            synced_connections: Default::default(),
+            watch_consensus_head_receiver: None,
+            watch_consensus_connections_sender,
             pending_transactions: Cache::builder()
                 .max_capacity(10_000)
                 .build_with_hasher(hashbrown::hash_map::DefaultHashBuilder::default()),
@@ -1350,9 +1394,13 @@ mod tests {
             (archive_rpc.name.clone(), archive_rpc.clone()),
         ]);
 
+        let (watch_consensus_connections_sender, _) = watch::channel(Default::default());
+
+        // TODO: make a Web3Connections::new
         let conns = Web3Connections {
             conns,
-            synced_connections: Default::default(),
+            watch_consensus_head_receiver: None,
+            watch_consensus_connections_sender,
             pending_transactions: Cache::builder()
                 .max_capacity(10)
                 .build_with_hasher(hashbrown::hash_map::DefaultHashBuilder::default()),

web3_proxy/src/rpcs/synced_connections.rs

@@ -1,4 +1,4 @@
-use super::blockchain::SavedBlock;
+use super::blockchain::{ArcBlock, SavedBlock};
 use super::connection::Web3Connection;
 use super::connections::Web3Connections;
 use ethers::prelude::{H256, U64};
@@ -43,31 +43,29 @@ impl fmt::Debug for ConsensusConnections {
 }
 
 impl Web3Connections {
-    pub fn head_block(&self) -> Option<SavedBlock> {
+    pub fn head_block(&self) -> Option<ArcBlock> {
-        self.synced_connections.load().head_block.clone()
+        self.watch_consensus_head_receiver
+            .as_ref()
+            .map(|x| x.borrow().clone())
     }
 
     pub fn head_block_hash(&self) -> Option<H256> {
-        self.synced_connections
+        self.head_block().and_then(|x| x.hash)
-            .load()
-            .head_block
-            .as_ref()
-            .map(|head_block| head_block.hash())
     }
 
     pub fn head_block_num(&self) -> Option<U64> {
-        self.synced_connections
+        self.head_block().and_then(|x| x.number)
-            .load()
-            .head_block
-            .as_ref()
-            .map(|head_block| head_block.number())
     }
 
     pub fn synced(&self) -> bool {
-        !self.synced_connections.load().conns.is_empty()
+        !self
+            .watch_consensus_connections_sender
+            .borrow()
+            .conns
+            .is_empty()
     }
 
     pub fn num_synced_rpcs(&self) -> usize {
-        self.synced_connections.load().conns.len()
+        self.watch_consensus_connections_sender.borrow().conns.len()
     }
 }