From 866000fcddffd3fb8dbdb0b811eee41cf5c6244a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Juli=C3=A1n=20Gonz=C3=A1lez=20Calder=C3=B3n?=
 <gonzalezcalderonjulian@gmail.com>
Date: Thu, 9 Jan 2025 18:25:51 -0300
Subject: [PATCH 1/3] Add fs2 dependency

---
 Cargo.lock                  | 1 +
 Cargo.toml                  | 1 +
 rpc-state-reader/Cargo.toml | 1 +
 3 files changed, 3 insertions(+)

diff --git a/Cargo.lock b/Cargo.lock
index 3d3b6f17..d2e3333d 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -6183,6 +6183,7 @@ dependencies = [
  "cairo-native",
  "cairo-vm",
  "flate2",
+ "fs2",
  "pretty_assertions_sorted",
  "serde",
  "serde_json",
diff --git a/Cargo.toml b/Cargo.toml
index f3a768e6..09b6f5a3 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -12,6 +12,7 @@ tracing = "0.1"
 serde_json = "1.0.116"
 serde_with = "3.11.0"
 serde = "1.0.197"
+fs2 = "0.4.3"
 cairo-native = { git = "https://github.com/lambdaclass/cairo_native.git", rev = "6a4efafa26d6a0424dee593d2091206c6e9f428d" }
 anyhow = "1.0"
 # Sequencer Dependencies
diff --git a/rpc-state-reader/Cargo.toml b/rpc-state-reader/Cargo.toml
index 0125c195..f223c5ec 100644
--- a/rpc-state-reader/Cargo.toml
+++ b/rpc-state-reader/Cargo.toml
@@ -30,6 +30,7 @@ starknet_gateway = { workspace = true }
 tracing = { workspace = true }
 anyhow.workspace = true
 sierra-emu.workspace = true
+fs2.workspace = true
 
 [dev-dependencies]
 pretty_assertions_sorted = "1.2.3"

From 6407ab473317e6ffb52ad925b655b1a527f87437 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Juli=C3=A1n=20Gonz=C3=A1lez=20Calder=C3=B3n?=
 <gonzalezcalderonjulian@gmail.com>
Date: Thu, 9 Jan 2025 18:44:33 -0300
Subject: [PATCH 2/3] Implement file locking and cache merging

---
 rpc-state-reader/src/cache.rs | 45 +++++++++++++++++++++++++++++++----
 1 file changed, 41 insertions(+), 4 deletions(-)

diff --git a/rpc-state-reader/src/cache.rs b/rpc-state-reader/src/cache.rs
index 1ce70879..0338a9e4 100644
--- a/rpc-state-reader/src/cache.rs
+++ b/rpc-state-reader/src/cache.rs
@@ -2,11 +2,13 @@ use std::{
     cell::RefCell,
     collections::{hash_map::Entry, HashMap},
     fs::{self, File},
+    io::Seek,
     path::PathBuf,
 };
 
 use blockifier::state::state_api::{StateReader as BlockifierStateReader, StateResult};
 use cairo_vm::Felt252;
+use fs2::FileExt;
 use serde::{Deserialize, Serialize};
 use serde_with::serde_as;
 use starknet::core::types::ContractClass;
@@ -59,8 +61,23 @@ impl Drop for RpcCachedStateReader {
         let path = PathBuf::from(format!("rpc_cache/{}.json", self.reader.block_number));
         let parent = path.parent().unwrap();
         fs::create_dir_all(parent).unwrap();
-        let file = File::create(path).unwrap();
-        serde_json::to_writer_pretty(file, &self.state).unwrap();
+
+        let mut file = File::options()
+            .read(true)
+            .write(true)
+            .create(true)
+            .open(path)
+            .unwrap();
+        file.lock_exclusive().unwrap();
+
+        if let Ok(new_state) = serde_json::from_reader::<_, RpcCache>(&file) {
+            merge_cache(self.state.get_mut(), new_state);
+        }
+        file.set_len(0).unwrap();
+        file.seek(std::io::SeekFrom::Start(0)).unwrap();
+
+        serde_json::to_writer_pretty(&file, &self.state).unwrap();
+        file.unlock().unwrap();
     }
 }
 
@@ -70,9 +87,14 @@ impl RpcCachedStateReader {
             let path = PathBuf::from(format!("rpc_cache/{}.json", reader.block_number));
 
             match File::open(path) {
-                Ok(file) => serde_json::from_reader(file).unwrap(),
+                Ok(file) => {
+                    file.lock_shared().unwrap();
+                    let state = serde_json::from_reader(&file).unwrap();
+                    file.unlock().unwrap();
+                    state
+                }
                 Err(_) => {
-                    warn!("Cache for block {} was not found", reader.block_number);
+                    warn!("Failed to read cache for block {}", reader.block_number);
                     RpcCache::default()
                 }
             }
@@ -220,3 +242,18 @@ impl BlockifierStateReader for RpcCachedStateReader {
         todo!();
     }
 }
+
+fn merge_cache(cache: &mut RpcCache, other: RpcCache) {
+    if cache.block.is_none() {
+        cache.block = other.block
+    }
+    cache.transactions.extend(other.transactions);
+    cache.contract_classes.extend(other.contract_classes);
+    cache.storage.extend(other.storage);
+    cache.nonces.extend(other.nonces);
+    cache.class_hashes.extend(other.class_hashes);
+    cache
+        .transaction_receipts
+        .extend(other.transaction_receipts);
+    cache.transaction_traces.extend(other.transaction_traces);
+}

From a7025c9df2556e355692e85095d648b55e3e0dd9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Juli=C3=A1n=20Gonz=C3=A1lez=20Calder=C3=B3n?=
 <gonzalezcalderonjulian@gmail.com>
Date: Fri, 10 Jan 2025 12:06:57 -0300
Subject: [PATCH 3/3] Clean up

---
 rpc-state-reader/src/cache.rs | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/rpc-state-reader/src/cache.rs b/rpc-state-reader/src/cache.rs
index 0338a9e4..82287a55 100644
--- a/rpc-state-reader/src/cache.rs
+++ b/rpc-state-reader/src/cache.rs
@@ -66,13 +66,17 @@ impl Drop for RpcCachedStateReader {
             .read(true)
             .write(true)
             .create(true)
+            .truncate(false)
             .open(path)
             .unwrap();
         file.lock_exclusive().unwrap();
 
-        if let Ok(new_state) = serde_json::from_reader::<_, RpcCache>(&file) {
-            merge_cache(self.state.get_mut(), new_state);
+        // try to read old cache, and merge it with the current one
+        if let Ok(old_state) = serde_json::from_reader::<_, RpcCache>(&file) {
+            merge_cache(self.state.get_mut(), old_state);
         }
+
+        // overwrite the file with the new cache
         file.set_len(0).unwrap();
         file.seek(std::io::SeekFrom::Start(0)).unwrap();