From 9c91d6492f227d9db172e634fae7fff099399c23 Mon Sep 17 00:00:00 2001
From: wsimon1982 <wsimon1982@googlemail.com>
Date: Mon, 9 Mar 2026 19:34:15 +0100
Subject: [PATCH] fix: close SQLite connections on exception in
 calculate_table_hash and _get_count

Fixes #767

Both calculate_table_hash() and _get_count() in RustChainSyncManager
opened a SQLite connection with _get_connection() but relied on reaching
conn.close() at the bottom of the function.  Any exception raised by
cursor.execute() or fetchall() / fetchone() would bypass conn.close(),
silently leaking the connection.

SQLite limits the number of open connections per process.  Under
sustained error conditions (e.g. disk I/O errors, locked DB) repeated
calls would exhaust that limit and make the node unable to open any new
database connections.

Wrap all cursor operations in try/finally blocks to guarantee conn.close()
is always called, mirroring the pattern already used in apply_sync_payload
and _load_table_schema.
---
 node/rustchain_sync.py | 37 ++++++++++++++++++++-----------------
 1 file changed, 20 insertions(+), 17 deletions(-)

diff --git a/node/rustchain_sync.py b/node/rustchain_sync.py
index e971746eb..ef7848cec 100644
--- a/node/rustchain_sync.py
+++ b/node/rustchain_sync.py
@@ -99,21 +99,22 @@ def calculate_table_hash(self, table_name: str) -> str:
         if not schema:
             return ""
 
-        conn = self._get_connection()
-        cursor = conn.cursor()
-
         pk = schema["pk"]
-        cursor.execute(f"SELECT * FROM {table_name} ORDER BY {pk} ASC")
-        rows = cursor.fetchall()
+        conn = self._get_connection()
+        try:
+            cursor = conn.cursor()
+            cursor.execute(f"SELECT * FROM {table_name} ORDER BY {pk} ASC")
+            rows = cursor.fetchall()
 
-        hasher = hashlib.sha256()
-        for row in rows:
-            row_dict = dict(row)
-            row_str = json.dumps(row_dict, sort_keys=True, separators=(",", ":"))
-            hasher.update(row_str.encode())
+            hasher = hashlib.sha256()
+            for row in rows:
+                row_dict = dict(row)
+                row_str = json.dumps(row_dict, sort_keys=True, separators=(",", ":"))
+                hasher.update(row_str.encode())
 
-        conn.close()
-        return hasher.hexdigest()
+            return hasher.hexdigest()
+        finally:
+            conn.close()
 
     def get_merkle_root(self) -> str:
         """Generates a master Merkle root hash for all synced tables."""
@@ -262,8 +263,10 @@ def _get_count(self, table_name: str) -> int:
         if table_name not in self.SYNC_TABLES:
             return 0
         conn = self._get_connection()
-        cursor = conn.cursor()
-        cursor.execute(f"SELECT COUNT(*) FROM {table_name}")
-        count = cursor.fetchone()[0]
-        conn.close()
-        return int(count)
+        try:
+            cursor = conn.cursor()
+            cursor.execute(f"SELECT COUNT(*) FROM {table_name}")
+            count = cursor.fetchone()[0]
+            return int(count)
+        finally:
+            conn.close()