Reduce outbound requests to eth1 endpoints (#2340)

## Issue Addressed

#2282 

## Proposed Changes

Reduce the outbound requests made to eth1 endpoints by caching the results from `eth_chainId` and `net_version`.
Further reduce the overall request count by increasing `auto_update_interval_millis` from `7_000` (7 seconds) to `60_000` (1 minute). 
This will result in a reduction from ~2000 requests per hour to 360 requests per hour (during normal operation). A reduction of 82%.

## Additional Info

If an endpoint fails, its state is dropped from the cache and the `eth_chainId` and `net_version` calls will be made for that endpoint again during the regular update cycle (once per minute) until it is back online.


Co-authored-by: Paul Hauner <paul@paulhauner.com>

beacon_node/eth1/src/inner.rs

@@ -2,10 +2,12 @@ use crate::Config;
 use crate::{
     block_cache::{BlockCache, Eth1Block},
     deposit_cache::{DepositCache, SszDepositCache},
+    service::EndpointsCache,
 };
 use parking_lot::RwLock;
 use ssz::{Decode, Encode};
 use ssz_derive::{Decode, Encode};
+use std::sync::Arc;
 use types::ChainSpec;
 
 #[derive(Default)]
@@ -28,6 +30,7 @@ impl DepositUpdater {
 pub struct Inner {
     pub block_cache: RwLock<BlockCache>,
     pub deposit_cache: RwLock<DepositUpdater>,
+    pub endpoints_cache: RwLock<Option<Arc<EndpointsCache>>>,
     pub config: RwLock<Config>,
     pub remote_head_block: RwLock<Option<Eth1Block>>,
     pub spec: ChainSpec,
@@ -87,6 +90,7 @@ impl SszEth1Cache {
                 cache: self.deposit_cache.to_deposit_cache()?,
                 last_processed_block: self.last_processed_block,
             }),
+            endpoints_cache: RwLock::new(None),
             // Set the remote head_block zero when creating a new instance. We only care about
             // present and future eth1 nodes.
             remote_head_block: RwLock::new(None),

beacon_node/eth1/src/service.rs

@@ -54,7 +54,27 @@ pub enum EndpointError {
 
 type EndpointState = Result<(), EndpointError>;
 
-type EndpointWithState = (SensitiveUrl, TRwLock<Option<EndpointState>>);
+pub struct EndpointWithState {
+    endpoint: SensitiveUrl,
+    state: TRwLock<Option<EndpointState>>,
+}
+
+impl EndpointWithState {
+    pub fn new(endpoint: SensitiveUrl) -> Self {
+        Self {
+            endpoint,
+            state: TRwLock::new(None),
+        }
+    }
+}
+
+async fn reset_endpoint_state(endpoint: &EndpointWithState) {
+    *endpoint.state.write().await = None;
+}
+
+async fn get_state(endpoint: &EndpointWithState) -> Option<EndpointState> {
+    *endpoint.state.read().await
+}
 
 /// A cache structure to lazily check usability of endpoints. An endpoint is usable if it is
 /// reachable and has the correct network id and chain id. Emits a `WARN` log if a checked endpoint
@@ -70,19 +90,19 @@ impl EndpointsCache {
     /// Checks the usability of an endpoint. Results get cached and therefore only the first call
     /// for each endpoint does the real check.
     async fn state(&self, endpoint: &EndpointWithState) -> EndpointState {
-        if let Some(result) = *endpoint.1.read().await {
+        if let Some(result) = *endpoint.state.read().await {
             return result;
         }
-        let mut value = endpoint.1.write().await;
+        let mut value = endpoint.state.write().await;
         if let Some(result) = *value {
             return result;
         }
         crate::metrics::inc_counter_vec(
             &crate::metrics::ENDPOINT_REQUESTS,
-            &[&endpoint.0.to_string()],
+            &[&endpoint.endpoint.to_string()],
         );
         let state = endpoint_state(
-            &endpoint.0,
+            &endpoint.endpoint,
             &self.config_network_id,
             &self.config_chain_id,
             &self.log,
@@ -92,7 +112,7 @@ impl EndpointsCache {
         if state.is_err() {
             crate::metrics::inc_counter_vec(
                 &crate::metrics::ENDPOINT_ERRORS,
-                &[&endpoint.0.to_string()],
+                &[&endpoint.endpoint.to_string()],
             );
             crate::metrics::set_gauge(&metrics::ETH1_CONNECTED, 0);
         } else {
@@ -114,12 +134,12 @@ impl EndpointsCache {
             .first_success(|endpoint| async move {
                 match self.state(endpoint).await {
                     Ok(()) => {
-                        let endpoint_str = &endpoint.0.to_string();
+                        let endpoint_str = &endpoint.endpoint.to_string();
                         crate::metrics::inc_counter_vec(
                             &crate::metrics::ENDPOINT_REQUESTS,
                             &[endpoint_str],
                         );
-                        match func(&endpoint.0).await {
+                        match func(&endpoint.endpoint).await {
                             Ok(t) => Ok(t),
                             Err(t) => {
                                 crate::metrics::inc_counter_vec(
@@ -127,7 +147,10 @@ impl EndpointsCache {
                                     &[endpoint_str],
                                 );
                                 if let SingleEndpointError::EndpointError(e) = &t {
-                                    *endpoint.1.write().await = Some(Err(*e));
+                                    *endpoint.state.write().await = Some(Err(*e));
+                                } else {
+                                    // A non-`EndpointError` error occurred, so reset the state.
+                                    reset_endpoint_state(endpoint).await;
                                 }
                                 Err(t)
                             }
@@ -138,6 +161,16 @@ impl EndpointsCache {
             })
             .await
     }
+
+    pub async fn reset_errorred_endpoints(&self) {
+        for endpoint in &self.fallback.servers {
+            if let Some(state) = get_state(endpoint).await {
+                if state.is_err() {
+                    reset_endpoint_state(endpoint).await;
+                }
+            }
+        }
+    }
 }
 
 /// Returns `Ok` if the endpoint is usable, i.e. is reachable and has a correct network id and
@@ -405,9 +438,9 @@ impl Default for Config {
             follow_distance: 128,
             node_far_behind_seconds: 128 * 14,
             block_cache_truncation: Some(4_096),
-            auto_update_interval_millis: 7_000,
+            auto_update_interval_millis: 60_000,
             blocks_per_log_query: 1_000,
-            max_log_requests_per_update: Some(100),
+            max_log_requests_per_update: Some(5_000),
             max_blocks_per_update: Some(8_192),
             purge_cache: false,
         }
@@ -435,6 +468,7 @@ impl Service {
                 deposit_cache: RwLock::new(DepositUpdater::new(
                     config.deposit_contract_deploy_block,
                 )),
+                endpoints_cache: RwLock::new(None),
                 remote_head_block: RwLock::new(None),
                 config: RwLock::new(config),
                 spec,
@@ -605,20 +639,31 @@ impl Service {
         self.inner.config.write().lowest_cached_block_number = block_number;
     }
 
-    pub fn init_endpoints(&self) -> EndpointsCache {
+    /// Builds a new `EndpointsCache` with empty states.
+    pub fn init_endpoints(&self) -> Arc<EndpointsCache> {
         let endpoints = self.config().endpoints.clone();
         let config_network_id = self.config().network_id.clone();
         let config_chain_id = self.config().chain_id.clone();
-        EndpointsCache {
-            fallback: Fallback::new(
-                endpoints
-                    .into_iter()
-                    .map(|s| (s, TRwLock::new(None)))
-                    .collect(),
-            ),
+        let new_cache = Arc::new(EndpointsCache {
+            fallback: Fallback::new(endpoints.into_iter().map(EndpointWithState::new).collect()),
             config_network_id,
             config_chain_id,
             log: self.log.clone(),
+        });
+
+        let mut endpoints_cache = self.inner.endpoints_cache.write();
+        *endpoints_cache = Some(new_cache.clone());
+        new_cache
+    }
+
+    /// Returns the cached `EndpointsCache` if it exists or builds a new one.
+    pub fn get_endpoints(&self) -> Arc<EndpointsCache> {
+        let endpoints_cache = self.inner.endpoints_cache.read();
+        if let Some(cache) = endpoints_cache.clone() {
+            cache
+        } else {
+            drop(endpoints_cache);
+            self.init_endpoints()
         }
     }
 
@@ -633,7 +678,11 @@ impl Service {
     pub async fn update(
         &self,
     ) -> Result<(DepositCacheUpdateOutcome, BlockCacheUpdateOutcome), String> {
-        let endpoints = self.init_endpoints();
+        let endpoints = self.get_endpoints();
+
+        // Reset the state of any endpoints which have errored so their state can be redetermined.
+        endpoints.reset_errorred_endpoints().await;
+
         let node_far_behind_seconds = self.inner.config.read().node_far_behind_seconds;
 
         let process_single_err = |e: &FallbackError<SingleEndpointError>| {
@@ -656,7 +705,7 @@ impl Service {
                     }
                 }
             }
-            endpoints.fallback.map_format_error(|s| &s.0, &e)
+            endpoints.fallback.map_format_error(|s| &s.endpoint, &e)
         };
 
         let process_err = |e: Error| match &e {

common/fallback/src/lib.rs

@@ -2,8 +2,9 @@ use itertools::{join, zip};
 use std::fmt::{Debug, Display};
 use std::future::Future;
 
+#[derive(Clone)]
 pub struct Fallback<T> {
-    servers: Vec<T>,
+    pub servers: Vec<T>,
 }
 
 #[derive(Debug, PartialEq)]