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On 11/07/14 19:20, Clark Boylan wrote:
> Before we get too far ahead of ourselves mysql-connector is not
> hosted on pypi. Instead it is an external package link. We recently
> managed to remove all packages that are hosted as external package
> links from openstack and will not add new ones in. Before we can
> use mysql-connector in the gate oracle will need to publish 
> mysql-connector on pypi properly.

There is misunderstanding in our community on how we deploy db client
modules. No project actually depends on any of them. We assume
deployers will install the proper one and configure 'connection'
string to use it. In case of devstack, we install the appropriate
package from distribution packages, not pip.

What we do is recommending a module for our users in our documentation.

That said, I assume the gate is a non-issue. Correct?

> 
> That said there is at least one other pure python alternative, 
> PyMySQL. PyMySQL supports py3k and pypy. We should look at using 
> PyMySQL instead if we want to start with a reasonable path to
> getting this in the gate.

MySQL Connector supports py3k too (not sure about pypy though).

> 
> Clark
> 
> On Fri, Jul 11, 2014 at 10:07 AM, Miguel Angel Ajo Pelayo 
> <mangelajo at redhat.com> wrote:
>> +1 here too,
>> 
>> Amazed with the performance gains, x2.4 seems a lot, and we'd get
>> rid of deadlocks.
>> 
>> 
>> 
>> ----- Original Message -----
>>> +1
>>> 
>>> I'm pretty excited about the possibilities here.  I've had
>>> this mysqldb/eventlet contention in the back of my mind for
>>> some time now. I'm glad to see some work being done in this
>>> area.
>>> 
>>> Carl
>>> 
>>> On Fri, Jul 11, 2014 at 7:04 AM, Ihar Hrachyshka
>>> <ihrachys at redhat.com> wrote:
> On 09/07/14 13:17, Ihar Hrachyshka wrote:
>>>>>> Hi all,
>>>>>> 
>>>>>> Multiple projects are suffering from db lock timeouts due
>>>>>> to deadlocks deep in mysqldb library that we use to
>>>>>> interact with mysql servers. In essence, the problem is
>>>>>> due to missing eventlet support in mysqldb module,
>>>>>> meaning when a db lock is encountered, the library does
>>>>>> not yield to the next green thread, allowing other 
>>>>>> threads to eventually unlock the grabbed lock, and
>>>>>> instead it just blocks the main thread, that eventually
>>>>>> raises timeout exception (OperationalError).
>>>>>> 
>>>>>> The failed operation is not retried, leaving failing
>>>>>> request not served. In Nova, there is a special retry
>>>>>> mechanism for deadlocks, though I think it's more a hack
>>>>>> than a proper fix.
>>>>>> 
>>>>>> Neutron is one of the projects that suffer from those
>>>>>> timeout errors a lot. Partly it's due to lack of
>>>>>> discipline in how we do nested calls in l3_db and
>>>>>> ml2_plugin code, but that's not something to change in
>>>>>> foreseeable future, so we need to find another solution
>>>>>> that is applicable for Juno. Ideally, the solution
>>>>>> should be applicable for Icehouse too to allow
>>>>>> distributors to resolve existing deadlocks without
>>>>>> waiting for Juno.
>>>>>> 
>>>>>> We've had several discussions and attempts to introduce a
>>>>>> solution to the problem. Thanks to oslo.db guys, we now
>>>>>> have more or less clear view on the cause of the failures
>>>>>> and how to easily fix them. The solution is to switch
>>>>>> mysqldb to something eventlet aware. The best candidate
>>>>>> is probably MySQL Connector module that is an official
>>>>>> MySQL client for Python and that shows some
>>>>>> (preliminary) good results in terms of performance.
> 
> I've made additional testing, creating 2000 networks in parallel
> (10 thread workers) for both drivers and comparing results.
> 
> With mysqldb: 215.81 sec With mysql-connector: 88.66
> 
> ~2.4 times performance boost, ok? ;)
> 
> I think we should switch to that library *even* if we forget about
> all the nasty deadlocks we experience now.
> 
>>>>>> 
>>>>>> I've posted a Neutron spec for the switch to the new
>>>>>> client in Juno at [1]. Ideally, switch is just a matter
>>>>>> of several fixes to oslo.db that would enable full
>>>>>> support for the new driver already supported by
>>>>>> SQLAlchemy, plus 'connection' string modified in service
>>>>>> configuration files, plus documentation updates to refer
>>>>>> to the new official way to configure services for MySQL.
>>>>>> The database code won't, ideally, require any major
>>>>>> changes, though some adaptation for the new client
>>>>>> library may be needed. That said, Neutron does not seem
>>>>>> to require any changes, though it was revealed that there
>>>>>> are some alembic migration rules in Keystone or Glance
>>>>>> that need (trivial) modifications.
>>>>>> 
>>>>>> You can see how trivial the switch can be achieved for a
>>>>>> service based on example for Neutron [2].
>>>>>> 
>>>>>> While this is a Neutron specific proposal, there is an
>>>>>> obvious wish to switch to the new library globally
>>>>>> throughout all the projects, to reduce devops burden,
>>>>>> among other things. My vision is that, ideally, we switch
>>>>>> all projects to the new library in Juno, though we still
>>>>>> may leave several projects for K in case any issues
>>>>>> arise, similar to the way projects switched to
>>>>>> oslo.messaging during two cycles instead of one. Though
>>>>>> looking at how easy Neutron can be switched to the new
>>>>>> library, I wouldn't expect any issues that would postpone
>>>>>> the switch till K.
>>>>>> 
>>>>>> It was mentioned in comments to the spec proposal that
>>>>>> there were some discussions at the latest summit around
>>>>>> possible switch in context of Nova that revealed some
>>>>>> concerns, though they do not seem to be documented
>>>>>> anywhere. So if you know anything about it, please
>>>>>> comment.
>>>>>> 
>>>>>> So, we'd like to hear from other projects what's your
>>>>>> take on that move, whether you see any issues or have
>>>>>> concerns about it.
>>>>>> 
>>>>>> Thanks for your comments, /Ihar
>>>>>> 
>>>>>> [1]: https://review.openstack.org/#/c/104905/ [2]: 
>>>>>> https://review.openstack.org/#/c/105209/
>>>>>> 
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>>>>>> OpenStack-dev mailing list
>>>>>> OpenStack-dev at lists.openstack.org 
>>>>>> http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
>>>>>>
>>>>
>>>>
>>>>>> 
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>>>> 
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