mysql: refuse to start if max_allowed_packet is too small

neo/storage/database/mysqldb.py

@@ -50,6 +50,8 @@ class MySQLDatabaseManager(DatabaseManager):
     # (tested with testOudatedCellsOnDownStorage).
     _use_partition = False
 
+    _max_allowed_packet = 32769 * 1024
+
     def __init__(self, *args, **kw):
         super(MySQLDatabaseManager, self).__init__(*args, **kw)
         self.conn = None
@@ -87,9 +89,18 @@ class MySQLDatabaseManager(DatabaseManager):
                 logging.exception('Connection to MySQL failed, retrying.')
                 time.sleep(1)
         self._active = 0
-        self.conn.autocommit(False)
-        self.conn.query("SET SESSION group_concat_max_len = %u" % (2**32-1))
-        self.conn.set_sql_mode("TRADITIONAL,NO_ENGINE_SUBSTITUTION")
+        conn = self.conn
+        conn.autocommit(False)
+        conn.query("SET SESSION group_concat_max_len = %u" % (2**32-1))
+        conn.set_sql_mode("TRADITIONAL,NO_ENGINE_SUBSTITUTION")
+        conn.query("SHOW VARIABLES WHERE variable_name='max_allowed_packet'")
+        r = conn.store_result()
+        (name, value), = r.fetch_row(r.num_rows())
+        if int(value) < self._max_allowed_packet:
+            raise DatabaseFailure("Global variable %r is too small."
+                " Minimal value must be %uk."
+                % (name, self._max_allowed_packet // 1024))
+        self._max_allowed_packet = int(value)
 
     def commit(self):
         logging.debug('committing...')

neo/tests/storage/testStorageMySQL.py

@@ -91,6 +91,25 @@ class StorageMySQLdbTests(StorageDBTests):
         self.assertEqual(self.db.escape('a"b'), 'a\\"b')
         self.assertEqual(self.db.escape("a'b"), "a\\'b")
 
+    def test_max_allowed_packet(self):
+        EXTRA = 2
+        # Check EXTRA
+        x = "SELECT '%s'" % ('x' * (self.db._max_allowed_packet - 11))
+        assert len(x) + EXTRA == self.db._max_allowed_packet
+        self.assertRaises(DatabaseFailure, self.db.query, x + ' ')
+        self.db.query(x)
+        # Check MySQLDatabaseManager._max_allowed_packet
+        query_list = []
+        query = self.db.query
+        self.db.query = lambda query: query_list.append(EXTRA + len(query))
+        self.assertEqual(2, max(len(self.db.escape(chr(x)))
+                                for x in xrange(256)))
+        self.assertEqual(2, len(self.db.escape('\0')))
+        self.db.storeData('\0' * 20, '\0' * (2**24-1), 0)
+        size, = query_list
+        max_allowed = self.db.__class__._max_allowed_packet
+        self.assertTrue(max_allowed - 1024 < size <= max_allowed, size)
+
 class StorageMySQLdbTokuDBTests(StorageMySQLdbTests):
 
     engine = "TokuDB"