feat: add weighted rpc steering

Author: DaMandal0rian

chain/ethereum/src/network.rs

@@ -6,6 +6,7 @@ use graph::components::network_provider::ProviderManager;
 use graph::components::network_provider::ProviderName;
 use graph::endpoint::EndpointMetrics;
 use graph::firehose::{AvailableCapacity, SubgraphLimit};
+use graph::prelude::rand::distributions::WeightedIndex;
 use graph::prelude::rand::seq::IteratorRandom;
 use graph::prelude::rand::{self, Rng};
 use itertools::Itertools;
@@ -30,6 +31,7 @@ pub struct EthereumNetworkAdapter {
     /// that limit. That's a somewhat imprecise but convenient way to
     /// determine the number of connections
     limit: SubgraphLimit,
+    weight: usize,
 }
 
 #[async_trait]
@@ -53,12 +55,14 @@ impl EthereumNetworkAdapter {
         capabilities: NodeCapabilities,
         adapter: Arc<EthereumAdapter>,
         limit: SubgraphLimit,
+        weight: usize,
     ) -> Self {
         Self {
             endpoint_metrics,
             capabilities,
             adapter,
             limit,
+            weight,
         }
     }
 
@@ -86,6 +90,7 @@ pub struct EthereumNetworkAdapters {
     call_only_adapters: Vec<EthereumNetworkAdapter>,
     // Percentage of request that should be used to retest errored adapters.
     retest_percent: f64,
+    weighted: bool,
 }
 
 impl EthereumNetworkAdapters {
@@ -95,6 +100,7 @@ impl EthereumNetworkAdapters {
             manager: ProviderManager::default(),
             call_only_adapters: vec![],
             retest_percent: DEFAULT_ADAPTER_ERROR_RETEST_PERCENT,
+            weighted: false,
         }
     }
 
@@ -121,14 +127,15 @@ impl EthereumNetworkAdapters {
             ProviderCheckStrategy::MarkAsValid,
         );
 
-        Self::new(chain_id, provider, call_only, None)
+        Self::new(chain_id, provider, call_only, None, false)
     }
 
     pub fn new(
         chain_id: ChainName,
         manager: ProviderManager<EthereumNetworkAdapter>,
         call_only_adapters: Vec<EthereumNetworkAdapter>,
         retest_percent: Option<f64>,
+        weighted: bool,
     ) -> Self {
         #[cfg(debug_assertions)]
         call_only_adapters.iter().for_each(|a| {
@@ -140,6 +147,7 @@ impl EthereumNetworkAdapters {
             manager,
             call_only_adapters,
             retest_percent: retest_percent.unwrap_or(DEFAULT_ADAPTER_ERROR_RETEST_PERCENT),
+            weighted,
         }
     }
 
@@ -192,31 +200,38 @@ impl EthereumNetworkAdapters {
     // handle adapter selection from a list, implements the availability checking with an abstracted
     // source of the adapter list.
     fn cheapest_from(
+        &self,
         input: Vec<&EthereumNetworkAdapter>,
         required_capabilities: &NodeCapabilities,
-        retest_percent: f64,
     ) -> Result<Arc<EthereumAdapter>, Error> {
         let retest_rng: f64 = (&mut rand::rng()).random();
 
-        let cheapest = input.into_iter().choose_multiple(&mut rand::rng(), 3);
-        let cheapest = cheapest.iter();
+        if retest_rng < self.retest_percent {
+            if let Some(adapter) = input.iter().max_by_key(|a| a.current_error_count()) {
+                return Ok(adapter.adapter.clone());
+            }
+        }
 
-        // If request falls below the retest threshold, use this request to try and
-        // reset the failed adapter. If a request succeeds the adapter will be more
-        // likely to be selected afterwards.
-        if retest_rng < retest_percent {
-            cheapest.max_by_key(|adapter| adapter.current_error_count())
+        if self.weighted {
+            if input.is_empty() {
+                return Err(anyhow!(
+                    "A matching Ethereum network with {:?} was not found.",
+                    required_capabilities
+                ));
+            }
+            let weights: Vec<_> = input.iter().map(|a| a.weight).collect();
+            if let Ok(dist) = WeightedIndex::new(&weights) {
+                let idx = dist.sample(&mut rand::rng());
+                return Ok(input[idx].adapter.clone());
+            }
         } else {
-            // The assumption here is that most RPC endpoints will not have limits
-            // which makes the check for low/high available capacity less relevant.
-            // So we essentially assume if it had available capacity when calling
-            // `all_cheapest_with` then it prolly maintains that state and so we
-            // just select whichever adapter is working better according to
-            // the number of errors.
-            cheapest.min_by_key(|adapter| adapter.current_error_count())
+            let choices = input.into_iter().choose_multiple(&mut rand::rng(), 3);
+            if let Some(adapter) = choices.iter().min_by_key(|a| a.current_error_count()) {
+                return Ok(adapter.adapter.clone());
+            }
         }
-        .map(|adapter| adapter.adapter.clone())
-        .ok_or(anyhow!(
+
+        Err(anyhow!(
             "A matching Ethereum network with {:?} was not found.",
             required_capabilities
         ))
@@ -226,13 +241,11 @@ impl EthereumNetworkAdapters {
         &self,
         required_capabilities: &NodeCapabilities,
     ) -> Result<Arc<EthereumAdapter>, Error> {
-        let cheapest = self.all_unverified_cheapest_with(required_capabilities);
+        let cheapest = self
+            .all_unverified_cheapest_with(required_capabilities)
+            .collect_vec();
 
-        Self::cheapest_from(
-            cheapest.choose_multiple(&mut rand::rng(), 3),
-            required_capabilities,
-            self.retest_percent,
-        )
+        self.cheapest_from(cheapest, required_capabilities)
     }
 
     /// This is the public entry point and should always use verified adapters
@@ -243,9 +256,9 @@ impl EthereumNetworkAdapters {
         let cheapest = self
             .all_cheapest_with(required_capabilities)
             .await
-            .choose_multiple(&mut rand::rng(), 3);
+            .collect_vec();
 
-        Self::cheapest_from(cheapest, required_capabilities, self.retest_percent)
+        self.cheapest_from(cheapest, required_capabilities)
     }
 
     pub async fn cheapest(&self) -> Option<Arc<EthereumAdapter>> {
@@ -429,6 +442,7 @@ mod tests {
                 },
                 eth_adapter.clone(),
                 SubgraphLimit::Limit(3),
+                1,
             )],
             vec![EthereumNetworkAdapter::new(
                 metrics.cheap_clone(),
@@ -438,6 +452,7 @@ mod tests {
                 },
                 eth_call_adapter.clone(),
                 SubgraphLimit::Limit(3),
+                1,
             )],
         )
         .await;
@@ -535,6 +550,7 @@ mod tests {
                 },
                 eth_call_adapter.clone(),
                 SubgraphLimit::Unlimited,
+                1,
             )],
             vec![EthereumNetworkAdapter::new(
                 metrics.cheap_clone(),
@@ -544,6 +560,7 @@ mod tests {
                 },
                 eth_adapter.clone(),
                 SubgraphLimit::Limit(2),
+                1,
             )],
         )
         .await;
@@ -606,6 +623,7 @@ mod tests {
                 },
                 eth_call_adapter.clone(),
                 SubgraphLimit::Disabled,
+                1,
             )],
             vec![EthereumNetworkAdapter::new(
                 metrics.cheap_clone(),
@@ -615,6 +633,7 @@ mod tests {
                 },
                 eth_adapter.clone(),
                 SubgraphLimit::Limit(3),
+                1,
             )],
         )
         .await;
@@ -661,6 +680,7 @@ mod tests {
                 },
                 eth_adapter.clone(),
                 SubgraphLimit::Limit(3),
+                1,
             )],
             vec![],
         )
@@ -756,11 +776,16 @@ mod tests {
             ProviderCheckStrategy::MarkAsValid,
         );
 
-        let no_retest_adapters =
-            EthereumNetworkAdapters::new(chain_id.clone(), manager.clone(), vec![], Some(0f64));
+        let no_retest_adapters = EthereumNetworkAdapters::new(
+            chain_id.clone(),
+            manager.clone(),
+            vec![],
+            Some(0f64),
+            false,
+        );
 
         let always_retest_adapters =
-            EthereumNetworkAdapters::new(chain_id, manager.clone(), vec![], Some(1f64));
+            EthereumNetworkAdapters::new(chain_id, manager.clone(), vec![], Some(1f64), false);
 
         assert_eq!(
             no_retest_adapters
@@ -844,8 +869,13 @@ mod tests {
             ProviderCheckStrategy::MarkAsValid,
         );
 
-        let always_retest_adapters =
-            EthereumNetworkAdapters::new(chain_id.clone(), manager.clone(), vec![], Some(1f64));
+        let always_retest_adapters = EthereumNetworkAdapters::new(
+            chain_id.clone(),
+            manager.clone(),
+            vec![],
+            Some(1f64),
+            false,
+        );
 
         assert_eq!(
             always_retest_adapters
@@ -869,7 +899,7 @@ mod tests {
         );
 
         let no_retest_adapters =
-            EthereumNetworkAdapters::new(chain_id.clone(), manager, vec![], Some(0f64));
+            EthereumNetworkAdapters::new(chain_id.clone(), manager, vec![], Some(0f64), false);
         assert_eq!(
             no_retest_adapters
                 .cheapest_with(&NodeCapabilities {
@@ -909,7 +939,8 @@ mod tests {
             ProviderCheckStrategy::MarkAsValid,
         );
 
-        let no_available_adapter = EthereumNetworkAdapters::new(chain_id, manager, vec![], None);
+        let no_available_adapter =
+            EthereumNetworkAdapters::new(chain_id, manager, vec![], None, false);
         let res = no_available_adapter
             .cheapest_with(&NodeCapabilities {
                 archive: true,

node/src/chain.rs

@@ -314,6 +314,7 @@ pub async fn create_ethereum_networks_for_chain(
                 .await,
             ),
             web3.limit_for(&config.node),
+            provider.weight,
         );
 
         if call_only {