On 04/30/2015 07:48 PM, Mike Bayer wrote:
On 4/30/15 11:00 AM, Victor Stinner wrote:
Hi,
I propose to replace mysql-python with mysqlclient in OpenStack
applications to get Python 3 support, bug fixes and some new features
(support MariaDB's libmysqlclient.so, support microsecond in TIME
column).
It is not feasible to use MySQLclient in Python 2 because it uses the
same module name as Python-MySQL, and would wreak havoc with distro
packaging and many other things.
I don't see what it would break. If I do:
Package: python-mysqlclient
Breaks: python-mysqldb
Replaces: python-mysqldb
Provides: python-mysqldb
everything is fine, and python-mysqlclient becomes another
implementation of the same thing. Then I believe it'd be a good idea to
simply remove python-mysqldb from Debian, since it's not maintained
upstream anymore.
It is also imprudent to switch
production openstack applications to a driver that is new and untested
(even though it is a port), nor is it necessary.
Supporting Python 3 is necessary, as we are going to remove Python 2
from Debian from Buster.
There should be no
reason Openstack applications are hardcoded to one database driver.
If they share the same "import mysqldb", and if they are API compatible,
how is this a problem?
The
approach should be simply that in Python 3, the mysqlclient library is
installed instead of mysql-python.
So, in Python 3, we'd have some bugfixes, and not in Python 2? This
seems a very weird approach to me, which *will* lead to lots of issues.
MySQLclient installs under the same
name, so in this case there isn't even any change to the SQLAlchemy URL
required.
Nor there should be in anything else, if they are completely API compatible.
PyMySQL is monkeypatchable, so as long as we are using eventlet, it is
*insane* that we are using MySQL-Python at all, because it is actively
making openstack applications perform much much more poorly than if we
just removed eventlet. So as long as eventlet is running, PyMySQL
wins the performance argument hands down (as described at the link
http://www.diamondtin.com/2014/sqlalchemy-gevent-mysql-python-drivers-comparison/
which is in the third paragraph of that wiki page). And it's Py3k
compatible.
Ok, so you are for switching to pymysql. Good. But is this realistic?
Are you going to provide yourself all the patches for absolutely all
projects of OpenStack that is using python-mysqldb?
1. keep Mysql-python on Py2K, use mysqlclient on py3k, changing the
implementation of the "MySQLdb" module on Py2K, server-wide, would be
very disruptive
I'm sorry to say it this way, because I respect you a lot and you did a
lot of very good things. But Mike, this is a very silly idea. We are
already having difficulties to push support for Py3, and in some cases,
it's hard to deal with the differences. Now, you want to add even more
source of problems, with bugs specific to Py2 or Py3 implementation? Why
should we make our life even more miserable? I completely fail to
understand what we would try to achieve by doing this.
2. if we actually care about performance, we either A. dump eventlet or
B. use pymysql. All other performance arguments are moot right now as
we are in the basement.
Eventlet has to die, we all know it. Not only for performances reason.
But this is completely orthogonal to the discussion we're having about
having Python 3 support. Please don't stand on the way to do it, just
because we have other (unrelated) issues with Eventlet + MySQL.
Switching to mysqlclient is basically almost "free" (by that, I mean
effortless), if I understand what Victor wrote. The same thing can't be
said of removing Eventlet or switching to pymysql, even though if both
may be needed. So why add the later as a blocker for the former?
Cheers,
Thomas Goirand (zigo)
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