feat: stale filters cleaner (#5080)

Co-authored-by: Matthias Seitz <matthias.seitz@outlook.de>

crates/rpc/rpc-builder/src/auth.rs

@@ -74,6 +74,7 @@ where
         eth_cache.clone(),
         DEFAULT_MAX_LOGS_PER_RESPONSE,
         Box::new(executor.clone()),
+        EthConfig::default().stale_filter_ttl,
     );
     launch_with_eth_api(eth_api, eth_filter, engine_api, socket_addr, secret).await
 }

crates/rpc/rpc-builder/src/eth.rs

@@ -39,8 +39,14 @@ pub struct EthConfig {
     ///
     /// Defaults to [RPC_DEFAULT_GAS_CAP]
     pub rpc_gas_cap: u64,
+    ///
+    /// Sets TTL for stale filters
+    pub stale_filter_ttl: std::time::Duration,
 }
 
+/// Default value for stale filter ttl
+const DEFAULT_STALE_FILTER_TTL: std::time::Duration = std::time::Duration::from_secs(5 * 60);
+
 impl Default for EthConfig {
     fn default() -> Self {
         Self {
@@ -49,6 +55,7 @@ impl Default for EthConfig {
             max_tracing_requests: DEFAULT_MAX_TRACING_REQUESTS,
             max_logs_per_response: DEFAULT_MAX_LOGS_PER_RESPONSE,
             rpc_gas_cap: RPC_DEFAULT_GAS_CAP.into(),
+            stale_filter_ttl: DEFAULT_STALE_FILTER_TTL,
         }
     }
 }

crates/rpc/rpc-builder/src/lib.rs

@@ -1044,6 +1044,7 @@ where
                 cache.clone(),
                 self.config.eth.max_logs_per_response,
                 executor.clone(),
+                self.config.eth.stale_filter_ttl,
             );
 
             let pubsub = EthPubSub::with_spawner(

crates/rpc/rpc/src/eth/filter.rs

@@ -17,8 +17,17 @@ use reth_rpc_api::EthFilterApiServer;
 use reth_rpc_types::{Filter, FilterBlockOption, FilterChanges, FilterId, FilteredParams, Log};
 use reth_tasks::TaskSpawner;
 use reth_transaction_pool::TransactionPool;
-use std::{collections::HashMap, iter::StepBy, ops::RangeInclusive, sync::Arc, time::Instant};
-use tokio::sync::{mpsc::Receiver, Mutex};
+use std::{
+    collections::HashMap,
+    iter::StepBy,
+    ops::RangeInclusive,
+    sync::Arc,
+    time::{Duration, Instant},
+};
+use tokio::{
+    sync::{mpsc::Receiver, Mutex},
+    time::MissedTickBehavior,
+};
 use tracing::trace;
 
 /// The maximum number of headers we read at once when handling a range filter.
@@ -30,19 +39,26 @@ pub struct EthFilter<Provider, Pool> {
     inner: Arc<EthFilterInner<Provider, Pool>>,
 }
 
-impl<Provider, Pool> EthFilter<Provider, Pool> {
+impl<Provider, Pool> EthFilter<Provider, Pool>
+where
+    Provider: Send + Sync + 'static,
+    Pool: Send + Sync + 'static,
+{
     /// Creates a new, shareable instance.
     ///
     /// This uses the given pool to get notified about new transactions, the provider to interact
     /// with the blockchain, the cache to fetch cacheable data, like the logs and the
     /// max_logs_per_response to limit the amount of logs returned in a single response
     /// `eth_getLogs`
+    ///
+    /// This also spawns a task that periodically clears stale filters.
     pub fn new(
         provider: Provider,
         pool: Pool,
         eth_cache: EthStateCache,
         max_logs_per_response: usize,
         task_spawner: Box<dyn TaskSpawner>,
+        stale_filter_ttl: Duration,
     ) -> Self {
         let inner = EthFilterInner {
             provider,
@@ -53,14 +69,51 @@ impl<Provider, Pool> EthFilter<Provider, Pool> {
             eth_cache,
             max_headers_range: MAX_HEADERS_RANGE,
             task_spawner,
+            stale_filter_ttl,
         };
-        Self { inner: Arc::new(inner) }
+
+        let eth_filter = Self { inner: Arc::new(inner) };
+
+        let this = eth_filter.clone();
+        eth_filter.inner.task_spawner.clone().spawn_critical(
+            "eth-filters_stale-filters-clean",
+            Box::pin(async move {
+                this.watch_and_clear_stale_filters().await;
+            }),
+        );
+
+        eth_filter
     }
 
     /// Returns all currently active filters
     pub fn active_filters(&self) -> &ActiveFilters {
         &self.inner.active_filters
     }
+
+    /// Endless future that [Self::clear_stale_filters] every `stale_filter_ttl` interval.
+    async fn watch_and_clear_stale_filters(&self) {
+        let mut interval = tokio::time::interval(self.inner.stale_filter_ttl);
+        interval.set_missed_tick_behavior(MissedTickBehavior::Delay);
+        loop {
+            interval.tick().await;
+            self.clear_stale_filters(Instant::now()).await;
+        }
+    }
+
+    /// Clears all filters that have not been polled for longer than the configured
+    /// `stale_filter_ttl` at the given instant.
+    pub async fn clear_stale_filters(&self, now: Instant) {
+        trace!(target: "rpc::eth", "clear stale filters");
+        self.active_filters().inner.lock().await.retain(|id, filter| {
+            let is_valid = (now - filter.last_poll_timestamp) < self.inner.stale_filter_ttl;
+
+            if !is_valid {
+                trace!(target: "rpc::eth", "evict filter with id: {:?}", id);
+            }
+
+            is_valid
+        })
+    }
 }
 
 impl<Provider, Pool> EthFilter<Provider, Pool>
@@ -244,7 +297,6 @@ impl<Provider, Pool> Clone for EthFilter<Provider, Pool> {
 #[derive(Debug)]
 struct EthFilterInner<Provider, Pool> {
     /// The transaction pool.
-    #[allow(unused)] // we need this for non standard full transactions eventually
     pool: Pool,
     /// The provider that can interact with the chain.
     provider: Provider,
@@ -259,8 +311,9 @@ struct EthFilterInner<Provider, Pool> {
     /// maximum number of headers to read at once for range filter
     max_headers_range: u64,
     /// The type that can spawn tasks.
-    #[allow(unused)]
     task_spawner: Box<dyn TaskSpawner>,
+    /// Duration since the last filter poll, after which the filter is considered stale
+    stale_filter_ttl: Duration,
 }
 
 impl<Provider, Pool> EthFilterInner<Provider, Pool>