fix: limit number of connections

zero_bin/leader/src/client.rs

@@ -45,7 +45,7 @@ pub(crate) async fn client_main(
             rpc_params.rpc_url.clone(),
             rpc_params.backoff,
             rpc_params.max_retries,
-        ),
+        )?,
     ));
     check_previous_proof_and_checkpoint(
         params.checkpoint_block_number,

zero_bin/rpc/src/jerigon.rs

@@ -29,7 +29,8 @@ where
 {
     // Grab trace information
     let tx_results = cached_provider
-        .as_provider()
+        .get_provider()
+        .await?
         .raw_request::<_, Vec<ZeroTxResult>>(
             "debug_traceBlockByNumber".into(),
             (target_block_id, json!({"tracer": "zeroTracer"})),
@@ -39,7 +40,8 @@ where
     // Grab block witness info (packed as combined trie pre-images)
 
     let block_witness = cached_provider
-        .as_provider()
+        .get_provider()
+        .await?
         .raw_request::<_, String>("eth_getWitness".into(), vec![target_block_id])
         .await?;
 

zero_bin/rpc/src/lib.rs

@@ -154,7 +154,7 @@ where
     // We use that execution not to produce a new contract bytecode - instead, we
     // return hashes. To look at the code use `cast disassemble <bytecode>`.
     let bytes = cached_provider
-        .as_provider()
+        .get_provider().await?
         .raw_request::<_, Bytes>(
             "eth_call".into(),
             (json!({"input": "0x60005B60010180430340816020025280610101116300000002576120205FF3"}), target_block_number),
@@ -216,7 +216,7 @@ where
         .header
         .number
         .context("target block is missing field `number`")?;
-    let chain_id = cached_provider.as_provider().get_chain_id().await?;
+    let chain_id = cached_provider.get_provider().await?.get_chain_id().await?;
     let prev_hashes = fetch_previous_block_hashes(cached_provider, target_block_number).await?;
 
     let other_data = OtherBlockData {

zero_bin/rpc/src/main.rs

@@ -117,7 +117,7 @@ impl Cli {
             self.config.rpc_url.clone(),
             self.config.backoff,
             self.config.max_retries,
-        )));
+        )?));
 
         match self.command {
             Command::Fetch {
@@ -141,7 +141,8 @@ impl Cli {
                 // Get transaction info.
                 match cached_provider
                     .clone()
-                    .as_provider()
+                    .get_provider()
+                    .await?
                     .get_transaction_by_hash(tx_hash)
                     .await?
                 {

zero_bin/rpc/src/native/mod.rs

@@ -1,4 +1,5 @@
 use std::collections::HashMap;
+use std::ops::Deref;
 use std::sync::Arc;
 
 use alloy::{
@@ -53,7 +54,7 @@ where
         .await?;
 
     let (code_db, txn_info) =
-        txn::process_transactions(&block, cached_provider.as_provider()).await?;
+        txn::process_transactions(&block, cached_provider.get_provider().await?.deref()).await?;
     let trie_pre_images = state::process_state_witness(cached_provider, block, &txn_info).await?;
 
     Ok(BlockTrace {

zero_bin/rpc/src/native/state.rs

@@ -182,7 +182,8 @@ where
             let provider = provider.clone();
             async move {
                 let proof = provider
-                    .as_provider()
+                    .get_provider()
+                    .await?
                     .get_proof(address, keys.into_iter().collect())
                     .block_id((block_number - 1).into())
                     .await
@@ -196,7 +197,8 @@ where
         let provider = provider.clone();
         async move {
             let proof = provider
-                .as_provider()
+                .get_provider()
+                .await?
                 .get_proof(address, keys.into_iter().collect())
                 .block_id(block_number.into())
                 .await

zero_bin/rpc/src/provider.rs

@@ -1,30 +1,57 @@
+use std::ops::{Deref, DerefMut};
 use std::sync::Arc;
 
 use alloy::primitives::BlockHash;
 use alloy::rpc::types::{Block, BlockId, BlockTransactionsKind};
 use alloy::{providers::Provider, transports::Transport};
 use anyhow::Context;
-use tokio::sync::Mutex;
+use tokio::sync::{Mutex, Semaphore, SemaphorePermit};
 
 const CACHE_SIZE: usize = 1024;
+const MAX_NUMBER_OF_PARALLEL_REQUESTS: usize = 64;
 
 /// Wrapper around alloy provider to cache blocks and other
 /// frequently used data.
 pub struct CachedProvider<ProviderT, TransportT> {
-    provider: ProviderT,
+    provider: Arc<ProviderT>,
+    // `Alloy` provider is using `Reqwest` http client under the hood. It has an unbounded
+    // connection pool. We need to limit the number of parallel connections by ourselves, so we
+    // use semaphore to count the number of parallel RPC requests happening at any moment with
+    // CachedProvider.
+    semaphore: Arc<Semaphore>,
     blocks_by_number: Arc<Mutex<lru::LruCache<u64, Block>>>,
     blocks_by_hash: Arc<Mutex<lru::LruCache<BlockHash, u64>>>,
     _phantom: std::marker::PhantomData<TransportT>,
 }
 
+pub struct ProviderGuard<'a, ProviderT> {
+    provider: Arc<ProviderT>,
+    _permit: SemaphorePermit<'a>,
+}
+
+impl<'a, ProviderT> Deref for ProviderGuard<'a, ProviderT> {
+    type Target = Arc<ProviderT>;
+
+    fn deref(&self) -> &Self::Target {
+        &self.provider
+    }
+}
+
+impl<ProviderT> DerefMut for ProviderGuard<'_, ProviderT> {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        &mut self.provider
+    }
+}
+
 impl<ProviderT, TransportT> CachedProvider<ProviderT, TransportT>
 where
     ProviderT: Provider<TransportT>,
     TransportT: Transport + Clone,
 {
     pub fn new(provider: ProviderT) -> Self {
         Self {
-            provider,
+            provider: provider.into(),
+            semaphore: Arc::new(Semaphore::new(MAX_NUMBER_OF_PARALLEL_REQUESTS)),
             blocks_by_number: Arc::new(Mutex::new(lru::LruCache::new(
                 std::num::NonZero::new(CACHE_SIZE).unwrap(),
             ))),
@@ -35,12 +62,11 @@ where
         }
     }
 
-    pub fn as_mut_provider(&mut self) -> &mut ProviderT {
-        &mut self.provider
-    }
-
-    pub const fn as_provider(&self) -> &ProviderT {
-        &self.provider
+    pub async fn get_provider(&self) -> Result<ProviderGuard<ProviderT>, anyhow::Error> {
+        Ok(ProviderGuard {
+            provider: self.provider.clone(),
+            _permit: self.semaphore.acquire().await?,
+        })
     }
 
     /// Retrieves block by number or hash, caching it if it's not already

zero_bin/rpc/src/retry.rs

@@ -1,9 +1,11 @@
+use std::time::Duration;
 use std::{
     future::Future,
     pin::Pin,
     task::{Context, Poll},
 };
 
+use alloy::transports::http::reqwest;
 use alloy::{
     providers::{ProviderBuilder, RootProvider},
     rpc::{
@@ -14,6 +16,9 @@ use alloy::{
 };
 use tower::{retry::Policy, Layer, Service};
 
+const HTTP_CLIENT_CONNECTION_POOL_IDLE_TIMEOUT: u64 = 90;
+const HTTP_CLIENT_MAX_IDLE_CONNECTIONS_PER_HOST: usize = 64;
+
 #[derive(Debug)]
 pub struct RetryPolicy {
     backoff: tokio::time::Duration,
@@ -138,11 +143,22 @@ pub fn build_http_retry_provider(
     rpc_url: url::Url,
     backoff: u64,
     max_retries: u32,
-) -> RootProvider<RetryService<alloy::transports::http::ReqwestTransport>> {
+) -> Result<RootProvider<RetryService<alloy::transports::http::ReqwestTransport>>, anyhow::Error> {
     let retry_policy = RetryLayer::new(RetryPolicy::new(
-        tokio::time::Duration::from_millis(backoff),
+        Duration::from_millis(backoff),
         max_retries,
     ));
-    let client = ClientBuilder::default().layer(retry_policy).http(rpc_url);
-    ProviderBuilder::new().on_client(client)
+    let reqwest_client = reqwest::ClientBuilder::new()
+        .pool_max_idle_per_host(HTTP_CLIENT_MAX_IDLE_CONNECTIONS_PER_HOST)
+        .pool_idle_timeout(Duration::from_secs(
+            HTTP_CLIENT_CONNECTION_POOL_IDLE_TIMEOUT,
+        ))
+        .build()?;
+
+    let http = alloy::transports::http::Http::with_client(reqwest_client, rpc_url);
+    let is_local = http.guess_local();
+    let client = ClientBuilder::default()
+        .layer(retry_policy)
+        .transport(http, is_local);
+    Ok(ProviderBuilder::new().on_client(client))
 }