fix: order pending txs by admission time

node/rustchain_tx_handler.py

@@ -84,6 +84,7 @@
 -- Index for faster queries
 CREATE INDEX IF NOT EXISTS idx_pending_from ON pending_transactions(from_addr);
 CREATE INDEX IF NOT EXISTS idx_pending_nonce ON pending_transactions(from_addr, nonce);
+CREATE INDEX IF NOT EXISTS idx_pending_admission ON pending_transactions(created_at, tx_hash);
 CREATE INDEX IF NOT EXISTS idx_history_from ON transaction_history(from_addr);
 CREATE INDEX IF NOT EXISTS idx_history_to ON transaction_history(to_addr);
 CREATE INDEX IF NOT EXISTS idx_history_block ON transaction_history(block_height);
@@ -170,6 +171,7 @@ def _ensure_schema(self):
                         if "already exists" not in str(e):
                             logger.warning(f"Schema statement failed: {e}")
 
+            self._ensure_pending_created_at(cursor)
             conn.commit()
 
     def _recover_interrupted_balances_migration(self, cursor) -> None:
@@ -193,6 +195,29 @@ def _recover_interrupted_balances_migration(self, cursor) -> None:
             cursor.execute("ALTER TABLE balances_old RENAME TO balances")
             logger.warning("Recovered interrupted balances migration from balances_old")
 
+    def _ensure_pending_created_at(self, cursor) -> None:
+        """Backfill admission-time ordering support for older pending tables."""
+        cursor.execute(
+            "SELECT name FROM sqlite_master WHERE type='table' AND name='pending_transactions'"
+        )
+        if not cursor.fetchone():
+            return
+        cursor.execute("PRAGMA table_info(pending_transactions)")
+        columns = [col[1] for col in cursor.fetchall()]
+        if "created_at" not in columns:
+            cursor.execute(
+                "ALTER TABLE pending_transactions ADD COLUMN created_at INTEGER NOT NULL DEFAULT 0"
+            )
+            if "timestamp" in columns:
+                cursor.execute(
+                    "UPDATE pending_transactions SET created_at = timestamp WHERE created_at = 0"
+                )
+            logger.info("Added created_at column to pending_transactions table")
+        cursor.execute(
+            "CREATE INDEX IF NOT EXISTS idx_pending_admission "
+            "ON pending_transactions(created_at, tx_hash)"
+        )
+
     @contextmanager
     def _get_connection(self):
         """Get database connection with proper locking"""
@@ -490,13 +515,13 @@ def submit_transaction(self, tx: SignedTransaction) -> Tuple[bool, str]:
                 return False, f"Transaction already exists: {e}"
 
     def get_pending_transactions(self, limit: int = 100) -> List[SignedTransaction]:
-        """Get pending transactions ordered by nonce"""
+        """Get pending transactions in deterministic admission order."""
         with self._get_connection() as conn:
             cursor = conn.cursor()
             cursor.execute(
                 """SELECT * FROM pending_transactions
                    WHERE status = 'pending'
-                   ORDER BY nonce ASC
+                   ORDER BY created_at ASC, tx_hash ASC
                    LIMIT ?""",
                 (limit,)
             )

tests/test_tx_handler_pending_order.py

@@ -0,0 +1,149 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: MIT
+"""Regression tests for pending transaction ordering."""
+
+import importlib
+import os
+import sqlite3
+import sys
+import types
+
+NODE_DIR = os.path.abspath(os.path.join(os.path.dirname(__file__), "..", "node"))
+if NODE_DIR not in sys.path:
+    sys.path.insert(0, NODE_DIR)
+
+mock = types.ModuleType("rustchain_crypto")
+
+
+class FakeSignedTransaction:
+    def __init__(
+        self,
+        from_addr,
+        to_addr,
+        amount_urtc,
+        nonce,
+        timestamp,
+        memo,
+        signature,
+        public_key,
+        tx_hash,
+    ):
+        self.from_addr = from_addr
+        self.to_addr = to_addr
+        self.amount_urtc = amount_urtc
+        self.nonce = nonce
+        self.timestamp = timestamp
+        self.memo = memo
+        self.signature = signature
+        self.public_key = public_key
+        self.tx_hash = tx_hash
+
+
+mock.SignedTransaction = FakeSignedTransaction  # type: ignore[attr-defined]
+mock.Ed25519Signer = object  # type: ignore[attr-defined]
+mock.blake2b256_hex = lambda data: "00" * 32  # type: ignore[attr-defined]
+mock.address_from_public_key = lambda data: "addr-from-pub"  # type: ignore[attr-defined]
+previous_crypto = sys.modules.get("rustchain_crypto")
+sys.modules["rustchain_crypto"] = mock
+
+TransactionPool = importlib.import_module("rustchain_tx_handler").TransactionPool
+
+if previous_crypto is None:
+    sys.modules.pop("rustchain_crypto", None)
+else:
+    sys.modules["rustchain_crypto"] = previous_crypto
+
+
+def _insert_pending(conn, tx_hash, from_addr, nonce, created_at):
+    conn.execute(
+        """INSERT INTO pending_transactions
+           (tx_hash, from_addr, to_addr, amount_urtc, nonce, timestamp,
+            memo, signature, public_key, created_at, status)
+           VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, 'pending')""",
+        (
+            tx_hash,
+            from_addr,
+            "receiver",
+            1,
+            nonce,
+            created_at,
+            "",
+            "sig",
+            "00",
+            created_at,
+        ),
+    )
+
+
+def test_pending_transactions_use_fifo_order_across_wallets(tmp_path):
+    pool = TransactionPool(str(tmp_path / "tx.db"))
+
+    with sqlite3.connect(pool.db_path) as conn:
+        _insert_pending(conn, "b" * 64, "wallet-a", 9, 100)
+        _insert_pending(conn, "a" * 64, "wallet-b", 1, 200)
+
+    pending = pool.get_pending_transactions()
+
+    assert [tx.tx_hash for tx in pending] == ["b" * 64, "a" * 64]
+
+
+def test_pending_transactions_use_hash_tiebreaker_for_same_admission_time(tmp_path):
+    pool = TransactionPool(str(tmp_path / "tx.db"))
+
+    with sqlite3.connect(pool.db_path) as conn:
+        _insert_pending(conn, "d" * 64, "wallet-a", 1, 100)
+        _insert_pending(conn, "c" * 64, "wallet-b", 1, 100)
+
+    pending = pool.get_pending_transactions()
+
+    assert [tx.tx_hash for tx in pending] == ["c" * 64, "d" * 64]
+
+
+def test_legacy_pending_table_gets_created_at_migration(tmp_path):
+    db_path = tmp_path / "legacy.db"
+    with sqlite3.connect(db_path) as conn:
+        conn.execute(
+            """CREATE TABLE balances (
+               wallet TEXT PRIMARY KEY,
+               balance_urtc INTEGER NOT NULL DEFAULT 0,
+               wallet_nonce INTEGER DEFAULT 0
+            )"""
+        )
+        conn.execute(
+            """CREATE TABLE pending_transactions (
+               tx_hash TEXT PRIMARY KEY,
+               from_addr TEXT NOT NULL,
+               to_addr TEXT NOT NULL,
+               amount_urtc INTEGER NOT NULL,
+               nonce INTEGER NOT NULL,
+               timestamp INTEGER NOT NULL,
+               memo TEXT DEFAULT '',
+               signature TEXT NOT NULL,
+               public_key TEXT NOT NULL,
+               status TEXT DEFAULT 'pending'
+            )"""
+        )
+        conn.execute(
+            """INSERT INTO pending_transactions
+               (tx_hash, from_addr, to_addr, amount_urtc, nonce, timestamp,
+                memo, signature, public_key, status)
+               VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, 'pending')""",
+            ("b" * 64, "wallet-a", "receiver", 1, 9, 100, "", "sig", "00"),
+        )
+        conn.execute(
+            """INSERT INTO pending_transactions
+               (tx_hash, from_addr, to_addr, amount_urtc, nonce, timestamp,
+                memo, signature, public_key, status)
+               VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, 'pending')""",
+            ("a" * 64, "wallet-b", "receiver", 1, 1, 200, "", "sig", "00"),
+        )
+
+    pool = TransactionPool(str(db_path))
+
+    with sqlite3.connect(db_path) as conn:
+        columns = [row[1] for row in conn.execute("PRAGMA table_info(pending_transactions)")]
+        assert "created_at" in columns
+
+    pending = pool.get_pending_transactions()
+
+    assert [tx.tx_hash for tx in pending] == ["b" * 64, "a" * 64]