Cache process const strings (#6952)

Author: LesnyRumcajs

src/lotus_json/arc.rs

@@ -23,3 +23,25 @@ impl<T: HasLotusJson + Clone> HasLotusJson for Arc<T> {
         Arc::new(T::from_lotus_json(lotus_json))
     }
 }
+
+// `Arc<str>` can't reuse the blanket impl above (which requires `T: Sized`,
+// and `str` is not). `Arc<str>` already satisfies every `HasLotusJson`
+// consumer bound directly (`Serialize + DeserializeOwned + JsonSchema +
+// Clone + 'static`), so we make `LotusJson = Self` and keep the conversions
+// as identity — serializing the cached value takes no allocation.
+impl HasLotusJson for Arc<str> {
+    type LotusJson = Self;
+
+    #[cfg(test)]
+    fn snapshots() -> Vec<(serde_json::Value, Self)> {
+        unimplemented!("tests are trivial for HasLotusJson<LotusJson = Self>")
+    }
+
+    fn into_lotus_json(self) -> Self::LotusJson {
+        self
+    }
+
+    fn from_lotus_json(lotus_json: Self::LotusJson) -> Self {
+        lotus_json
+    }
+}

src/rpc/methods/eth.rs

@@ -77,7 +77,7 @@ use serde::{Deserialize, Serialize};
 use std::num::NonZeroUsize;
 use std::ops::RangeInclusive;
 use std::str::FromStr;
-use std::sync::{Arc, LazyLock};
+use std::sync::{Arc, LazyLock, OnceLock};
 use utils::{decode_payload, lookup_eth_address};
 
 static FOREST_TRACE_FILTER_MAX_RESULT: LazyLock<u64> =
@@ -764,17 +764,23 @@ impl RpcMethod<0> for Web3ClientVersion {
     const PERMISSION: Permission = Permission::Read;
 
     type Params = ();
-    type Ok = String;
+    type Ok = Arc<str>;
 
     async fn handle(
         _: Ctx<impl Blockstore + Send + Sync + 'static>,
         (): Self::Params,
         _: &http::Extensions,
     ) -> Result<Self::Ok, ServerError> {
-        Ok(format!(
-            "forest/{}",
-            *crate::utils::version::FOREST_VERSION_STRING
-        ))
+        // Version string is baked in at build time; cache once.
+        static CACHED: OnceLock<Arc<str>> = OnceLock::new();
+        Ok(CACHED
+            .get_or_init(|| {
+                Arc::<str>::from(format!(
+                    "forest/{}",
+                    *crate::utils::version::FOREST_VERSION_STRING
+                ))
+            })
+            .clone())
     }
 }
 
@@ -844,14 +850,18 @@ impl RpcMethod<0> for EthChainId {
     const PERMISSION: Permission = Permission::Read;
 
     type Params = ();
-    type Ok = String;
+    type Ok = Arc<str>;
 
     async fn handle(
         ctx: Ctx<impl Blockstore + Send + Sync + 'static>,
         (): Self::Params,
         _: &http::Extensions,
     ) -> Result<Self::Ok, ServerError> {
-        Ok(format!("{:#x}", ctx.chain_config().eth_chain_id))
+        // `eth_chain_id` is fixed for the process lifetime; cache the hex form.
+        static CACHED: OnceLock<Arc<str>> = OnceLock::new();
+        Ok(CACHED
+            .get_or_init(|| Arc::<str>::from(format!("{:#x}", ctx.chain_config().eth_chain_id)))
+            .clone())
     }
 }
 

src/rpc/methods/f3.rs

@@ -63,14 +63,20 @@ impl RpcMethod<0> for GetRawNetworkName {
     const PERMISSION: Permission = Permission::Read;
 
     type Params = ();
-    type Ok = String;
+    type Ok = Arc<str>;
 
     async fn handle(
         ctx: Ctx<impl Blockstore>,
         (): Self::Params,
         _: &http::Extensions,
     ) -> Result<Self::Ok, ServerError> {
-        Ok(ctx.chain_config().network.genesis_name().into())
+        // Network is fixed for the process lifetime; cache the genesis name.
+        static CACHED: OnceLock<Arc<str>> = OnceLock::new();
+        Ok(CACHED
+            .get_or_init(|| {
+                Arc::<str>::from(String::from(ctx.chain_config().network.genesis_name()))
+            })
+            .clone())
     }
 }
 

src/rpc/methods/net.rs

@@ -7,6 +7,7 @@ pub use types::*;
 use std::any::Any;
 use std::num::NonZeroU64;
 use std::str::FromStr;
+use std::sync::{Arc, OnceLock};
 use std::time::Instant;
 
 use crate::libp2p::chain_exchange::TipsetBundle;
@@ -282,14 +283,18 @@ impl RpcMethod<0> for NetVersion {
     const NAME_ALIAS: Option<&'static str> = Some("net_version");
 
     type Params = ();
-    type Ok = String;
+    type Ok = Arc<str>;
 
     async fn handle(
         ctx: Ctx<impl Blockstore>,
         (): Self::Params,
         _: &http::Extensions,
     ) -> Result<Self::Ok, ServerError> {
-        Ok(ctx.chain_config().eth_chain_id.to_string())
+        // `eth_chain_id` is fixed for the process lifetime; cache the decimal form.
+        static CACHED: OnceLock<Arc<str>> = OnceLock::new();
+        Ok(CACHED
+            .get_or_init(|| Arc::<str>::from(ctx.chain_config().eth_chain_id.to_string()))
+            .clone())
     }
 }