From 41d8a86df4889ae6c1619c93fcaf3a8d9f997c10 Mon Sep 17 00:00:00 2001
From: Renato Dinhani <101204870+dinhani-cw@users.noreply.github.com>
Date: Wed, 24 Apr 2024 14:51:14 -0300
Subject: [PATCH] feat: conflict detection between executions (#690)

---
 src/eth/primitives/execution.rs               | 49 +++++++++++++++++++
 src/eth/primitives/execution_conflict.rs      | 18 +++----
 .../postgres_permanent/postgres_permanent.rs  | 10 +++-
 3 files changed, 63 insertions(+), 14 deletions(-)

diff --git a/src/eth/primitives/execution.rs b/src/eth/primitives/execution.rs
index 1194aa140..eb8cc40b4 100644
--- a/src/eth/primitives/execution.rs
+++ b/src/eth/primitives/execution.rs
@@ -16,6 +16,8 @@ use crate::eth::primitives::Account;
 use crate::eth::primitives::Address;
 use crate::eth::primitives::Bytes;
 use crate::eth::primitives::ExecutionAccountChanges;
+use crate::eth::primitives::ExecutionConflicts;
+use crate::eth::primitives::ExecutionConflictsBuilder;
 use crate::eth::primitives::ExecutionResult;
 use crate::eth::primitives::ExternalBlock;
 use crate::eth::primitives::ExternalReceipt;
@@ -104,6 +106,53 @@ impl Execution {
         None
     }
 
+    /// Checks conflicts between two executions.
+    ///
+    /// Assumes self is the present execution and next should happen after self in a serialized context.
+    pub fn check_conflicts(&self, next_execution: &Execution) -> Option<ExecutionConflicts> {
+        let mut conflicts = ExecutionConflictsBuilder::default();
+
+        for current in self.changes.values() {
+            let Some(next) = next_execution.changes.get(&current.address) else {
+                continue;
+            };
+
+            // nonce conflict
+            let current_nonce = current.nonce.take_modified_ref();
+            let next_nonce = next.nonce.take_original_ref();
+            match (current_nonce, next_nonce) {
+                (Some(current_nonce), Some(next_nonce)) if current_nonce != next_nonce => {
+                    conflicts.add_nonce(current.address, *current_nonce, *next_nonce);
+                }
+                _ => {}
+            }
+
+            // balance conflict
+            let current_balance = current.balance.take_modified_ref();
+            let next_balance = next.balance.take_original_ref();
+            match (current_balance, next_balance) {
+                (Some(current_balance), Some(next_balance)) if current_balance != next_balance => {
+                    conflicts.add_balance(current.address, *current_balance, *next_balance);
+                }
+                _ => {}
+            }
+
+            // slot conflicts
+            for (slot_index, current_slot_change) in &current.slots {
+                let current_slot = current_slot_change.take_modified_ref();
+                let next_slot = next.slots.get(slot_index).and_then(|slot| slot.take_original_ref());
+                match (current_slot, next_slot) {
+                    (Some(current_slot), Some(next_slot)) if current_slot != next_slot => {
+                        conflicts.add_slot(current.address, *slot_index, current_slot.value, next_slot.value);
+                    }
+                    _ => {}
+                }
+            }
+        }
+
+        conflicts.build()
+    }
+
     /// Checks if current execution state matches the information present in the external receipt.
     pub fn compare_with_receipt(&self, receipt: &ExternalReceipt) -> anyhow::Result<()> {
         // compare execution status
diff --git a/src/eth/primitives/execution_conflict.rs b/src/eth/primitives/execution_conflict.rs
index 13503008b..045e948a0 100644
--- a/src/eth/primitives/execution_conflict.rs
+++ b/src/eth/primitives/execution_conflict.rs
@@ -46,18 +46,10 @@ impl ExecutionConflictsBuilder {
 #[derive(Debug)]
 pub enum ExecutionConflict {
     /// Account nonce mismatch.
-    Nonce {
-        address: Address,
-        expected: Nonce,
-        actual: Nonce,
-    },
+    Nonce { address: Address, expected: Nonce, actual: Nonce },
 
     /// Account balance mismatch.
-    Balance {
-        address: Address,
-        expected: Wei,
-        actual: Wei,
-    },
+    Balance { address: Address, expected: Wei, actual: Wei },
 
     /// Slot value mismatch.
     Slot {
@@ -67,7 +59,9 @@ pub enum ExecutionConflict {
         actual: SlotValue,
     },
 
-    Account,
+    /// Number of modified accounts mismatch.
+    AccountModifiedCount { expected: usize, actual: usize },
 
-    PgSlot,
+    /// Number of modified slots mismatch.
+    SlotModifiedCount { expected: usize, actual: usize },
 }
diff --git a/src/eth/storage/postgres_permanent/postgres_permanent.rs b/src/eth/storage/postgres_permanent/postgres_permanent.rs
index 88b1d65a2..1552a40e2 100644
--- a/src/eth/storage/postgres_permanent/postgres_permanent.rs
+++ b/src/eth/storage/postgres_permanent/postgres_permanent.rs
@@ -689,13 +689,19 @@ impl PermanentStorage for PostgresPermanentStorage {
 
         if modified_accounts != expected_modified_accounts {
             tx.rollback().await.context("failed to rollback transaction")?;
-            let error: StorageError = StorageError::Conflict(ExecutionConflicts(nonempty![ExecutionConflict::Account]));
+            let error: StorageError = StorageError::Conflict(ExecutionConflicts(nonempty![ExecutionConflict::AccountModifiedCount {
+                expected: expected_modified_accounts,
+                actual: modified_accounts,
+            }]));
             return Err(error);
         }
 
         if modified_slots != expected_modified_slots {
             tx.rollback().await.context("failed to rollback transaction")?;
-            let error: StorageError = StorageError::Conflict(ExecutionConflicts(nonempty![ExecutionConflict::PgSlot]));
+            let error: StorageError = StorageError::Conflict(ExecutionConflicts(nonempty![ExecutionConflict::SlotModifiedCount {
+                expected: expected_modified_slots,
+                actual: modified_slots
+            }]));
             return Err(error);
         }