nova team mailing list archive

[Eric Day <eday@xxxxxxxxxxxx>]

Hi Vish,

I completely agree, add more tests first and do it gradually. As
Michael said we'll probably start with the rackspace/openstack API
that Todd was working on to make sure it looks solid and integrates
well, and then from there we can start with the other services.

-Eric

On Wed, Aug 04, 2010 at 09:45:22AM -0700, Vishvananda Ishaya wrote:
>    If we are going to go through a major rewrite, I would suggest that we
>    spend some serious time improving our test coverage, especially
>    integration/smoketests. We need to know when our changes are breaking
>    things.  Any manpower that we can devote to this now will dramatically
>    decrease the pain of switching over components in the future.  I think
>    switching one component at a time is probably the right way to go as well.
>    Vish
>    On Wed, Aug 4, 2010 at 9:03 AM, Michael Gundlach
>    <michael.gundlach@xxxxxxxxxxxxx> wrote:
> 
>      All,
>      I propose that we go ahead and decide to use Eventlet.  We've all had a
>      chance to talk, the decision isn't going to make itself, and it seems
>      like we're coalescing around Eventlet:
>        * In a long discussion about how to keep our code loosely coupled and
>          easy to maintain (see Architecture For Shared Components on the
>          openstack list), we concluded that WSGI would be a great solution,
>          and eday has prototyped an Eventlet-powered WSGI app talking AMQP to
>          Rabbit.  The Twisted WSGI approach apparently isn't stable or
>          standard, but WSGI works just as you'd expect in Eventlet.
>        * As hazmat points out in the "twisted v. eventlet" thread, you can't
>          use pdb with Twisted, while pdb works just as you'd hope in
>          Eventlet.
>        * hazmat's experience during his lightning talk (see the same thread)
>          is a good datapoint verifying that people unfamiliar with either
>          project will probably prefer to work with Eventlet over Twisted:
>          good for recruiting.
>        * It's a weaker argument, but it's really hard to find any comparisons
>          between Twisted and Eventlet on the web that say Twisted is
>          preferable (has anyone found any?)
>      And as always, there's the argument that Eventlet code is easier to read
>      and understand, and therefore to maintain.
>      I'm going to be working on adding the RS API to Nova, and I'm going to
>      proceed in Eventlet.  If anyone feels strongly that we must use Twisted
>      instead, speak up; otherwise, shall we call this decision made?
>      trying-to-build-consensus-ly yrs,
>      Michael
>      On Tue, Aug 3, 2010 at 8:13 AM, Soren Hansen
>      <soren.hansen@xxxxxxxxxxxxx> wrote:
> 
>        On Mon, Aug 02, 2010 at 05:21:23PM -0500, Eric Day wrote:
>        > I took a closer look at the inner workings of how Twisted is
>        currently
>        > being used, and I think there is still a good chunk of work to be
>        done
>        > to make things work properly. For example, both Redis and AMQP
>        modules
>        > are not using the Twisted I/O event loop. Both are still issuing
>        sync
>        > socket calls in their own libs which could block the entire
>        > application.
> 
>        Yup, this definitely needs fixing.
>        > These things are very doable in Twisted, it will just require using
>        > the txRedis and txAMQP modules. It will also introduce more
>        deferreds
>        > into the mix since we'll have non-blocking connections dependent on
>        > each other. From this perspective, Eventlet may be easier since we
>        > could still use the current libraries by patching
>        > (http://eventlet.net/doc/patching.html).
> 
>        Yes, both python-redis and python-amqplib use Python's standard socket
>        module, so they can be patched.
> 
>        Does anyone know how eventlet would deal with libvirt calls?
>        python-libvirt just calls into libvirt obviously doesn't use Python's
>        socket module.
>        --
>        Soren Hansen
>        Systems Architect
>        The Rackspace Cloud
> 
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