BUG30764641: Fix dnspython dependency

In the WL#13372 implementation, the dnspython module dependency was added
for host configuration using DNS SRV.

This patch removes the need of having dnspython installed if no DNS SRV
functionality is not being used. But raises an exception if it's used.

Author: nmariz

docs/mysqlx/requirements.rst

@@ -3,6 +3,6 @@ Requirements
 
 * MySQL 8.0.0 or higher, with the X Plugin enabled
 * Python 2.7 or >= 3.4
-* Protobuf C++ (version >= 3.6.1)
-* Python Protobuf (version >= 3.6.1)
-* dnspython (version==1.16.0)
+* Protobuf C++ (version >= 3.0.0)
+* Python Protobuf (version >= 3.0.0)
+* dnspython (version >= 1.16.0)

docs/mysqlx/tutorials/getting_started.rst

@@ -190,6 +190,8 @@ Resolving DNS SRV records
 
 If you are using a DNS server with service discovery utility that supports mapping `SRV records <https://tools.ietf.org/html/rfc2782>`_, you can use the ``mysqlx+srv`` scheme or ``dns-srv`` connection option and Connector/Python will automatically resolve the available server addresses described by those SRV records.
 
+.. note:: MySQL host configuration using DNS SRV requires `dnspython <http://www.dnspython.org/>`_ module.
+
 .. code-block:: python
 
    session = mysqlx.get_session('mysqlx://root:@foo.abc.com')

lib/mysql/connector/__init__.py

@@ -1,4 +1,4 @@
-# Copyright (c) 2009, 2019, Oracle and/or its affiliates. All rights reserved.
+# Copyright (c) 2009, 2020, Oracle and/or its affiliates. All rights reserved.
 #
 # This program is free software; you can redistribute it and/or modify
 # it under the terms of the GNU General Public License, version 2.0, as
@@ -38,8 +38,14 @@
 else:
     HAVE_CEXT = True
 
-import dns.resolver
-import dns.exception
+try:
+    import dns.resolver
+    import dns.exception
+except ImportError:
+    HAVE_DNSPYTHON = False
+else:
+    HAVE_DNSPYTHON = True
+
 import random
 
 from . import version
@@ -189,6 +195,10 @@ def connect(*args, **kwargs):
         raise InterfaceError("The value of 'dns-srv' must be a boolean")
 
     if dns_srv:
+        if not HAVE_DNSPYTHON:
+            raise InterfaceError('MySQL host configuration requested DNS '
+                                 'SRV. This requires the Python dnspython '
+                                 'module. Please refer to documentation')
         if 'unix_socket' in kwargs:
             raise InterfaceError('Using Unix domain sockets with DNS SRV '
                                  'lookup is not allowed')

lib/mysqlx/connection.py

@@ -1,4 +1,4 @@
-# Copyright (c) 2016, 2019, Oracle and/or its affiliates. All rights reserved.
+# Copyright (c) 2016, 2020, Oracle and/or its affiliates. All rights reserved.
 #
 # This program is free software; you can redistribute it and/or modify
 # it under the terms of the GNU General Public License, version 2.0, as
@@ -58,8 +58,13 @@
 import re
 import threading
 
-import dns.resolver
-import dns.exception
+try:
+    import dns.resolver
+    import dns.exception
+except ImportError:
+    HAVE_DNSPYTHON = False
+else:
+    HAVE_DNSPYTHON = True
 
 from datetime import datetime, timedelta
 from functools import wraps
@@ -1716,6 +1721,10 @@ def __init__(self, settings):
 
         # Check for DNS SRV
         if settings.get("host") and settings.get("dns-srv"):
+            if not HAVE_DNSPYTHON:
+                raise InterfaceError("MySQL host configuration requested DNS "
+                                     "SRV. This requires the Python dnspython "
+                                     "module. Please refer to documentation")
             try:
                 srv_records = dns.resolver.query(settings["host"], "SRV")
             except dns.exception.DNSException:

setup.py

@@ -1,7 +1,7 @@
 #!/usr/bin/env python
 # -*- coding: utf-8 -*-
 
-# Copyright (c) 2009, 2017, Oracle and/or its affiliates. All rights reserved.
+# Copyright (c) 2009, 2020, Oracle and/or its affiliates. All rights reserved.
 #
 # This program is free software; you can redistribute it and/or modify
 # it under the terms of the GNU General Public License, version 2.0, as
@@ -69,5 +69,6 @@
     cmdclass=setupinfo.command_classes,
     ext_modules=setupinfo.extensions,
     install_requires=setupinfo.install_requires,
+    extras_require=setupinfo.extras_require,
 )
 

setupinfo.py

@@ -139,4 +139,5 @@
     'Topic :: Software Development :: Libraries :: Application Frameworks',
     'Topic :: Software Development :: Libraries :: Python Modules'
 ]
-install_requires = ["protobuf>=3.6.1", "dnspython==1.16.0"]
+install_requires = ["protobuf>=3.0.0"],
+extras_require = {"dns-srv": ["dnspython>=1.16.0"]}

tests/test_connection.py

@@ -1,4 +1,4 @@
-# Copyright (c) 2009, 2019, Oracle and/or its affiliates. All rights reserved.
+# Copyright (c) 2009, 2020, Oracle and/or its affiliates. All rights reserved.
 #
 # This program is free software; you can redistribute it and/or modify
 # it under the terms of the GNU General Public License, version 2.0, as
@@ -53,7 +53,8 @@
 
 from mysql.connector.conversion import (MySQLConverterBase, MySQLConverter)
 from mysql.connector import (connect, connection, network, errors,
-                             constants, cursor, abstracts, catch23)
+                             constants, cursor, abstracts, catch23,
+                             HAVE_DNSPYTHON)
 from mysql.connector.errors import InterfaceError
 from mysql.connector.optionfiles import read_option_files
 from mysql.connector.network import TLS_V1_3_SUPPORTED
@@ -2155,6 +2156,8 @@ def test_connection_attributes_user_defined(self):
 
     @unittest.skipIf(tests.MYSQL_VERSION < (8, 0, 19),
                      "MySQL 8.0.19+ is required for DNS SRV")
+    @unittest.skipIf(not HAVE_DNSPYTHON,
+                     "dnspython module is required for DNS SRV")
     def test_dns_srv(self):
         config = tests.get_mysql_config().copy()
         config.pop("unix_socket", None)

tests/test_mysqlx_connection.py

@@ -1,6 +1,6 @@
 # -*- coding: utf-8 -*-
 
-# Copyright (c) 2016, 2019, Oracle and/or its affiliates. All rights reserved.
+# Copyright (c) 2016, 2020, Oracle and/or its affiliates. All rights reserved.
 #
 # This program is free software; you can redistribute it and/or modify
 # it under the terms of the GNU General Public License, version 2.0, as
@@ -46,8 +46,7 @@
 from time import sleep
 
 from . import check_tls_versions_support
-from mysqlx.connection import SocketStream
-from mysqlx.connection import TLS_V1_3_SUPPORTED
+from mysqlx.connection import SocketStream, TLS_V1_3_SUPPORTED, HAVE_DNSPYTHON
 from mysqlx.compat import STRING_TYPES
 from mysqlx.errors import InterfaceError, OperationalError, ProgrammingError
 from mysqlx.protocol import  Message, MessageReaderWriter, Protocol
@@ -1532,6 +1531,8 @@ def test_connection_attributes(self):
 
     @unittest.skipIf(tests.MYSQL_VERSION < (8, 0, 19),
                      "MySQL 8.0.19+ is required for DNS SRV")
+    @unittest.skipIf(not HAVE_DNSPYTHON,
+                     "dnspython module is required for DNS SRV")
     def test_dns_srv(self):
         # The value of 'dns-srv' must be a boolean
         uri = "root:@localhost/myschema?dns-srv=invalid"