++ On 08/04/2010 09:23 AM, Eric Day wrote: > Hi Michael, > > ++ On all points. Over the past few days while researching all this, > I went from being in the middle to the Eventlet side. Another couple > points to make: > > * We are not actually using twisted for what it is powerful for - > non-blocking I/O handling. The AMQP and Redis libs are still using > blocking sockets and queues are being polled with a timer every 100ms > with sync operations. There is still some work to be done to use > it properly (replacing libs with twisted versions, restructure app). > > * The places we are using twisted currently may not even need this, > using a multi-process or multi-thread model may make more sense. See > active thread discussing this right now. > > * The application where we do need twisted/eventlet - nova-api - is > currently still on tornado, so we can start using eventlet there and > don't need to worry about converting twisted code already written > (no wasted resources). > > * We have eventlet experts and a large scale app already on hand > with swift, so we can bug them with any questions. :) > > -Eric > > On Wed, Aug 04, 2010 at 12:03:49PM -0400, Michael Gundlach 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 <[email protected]> >> 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 >> >> _______________________________________________ >> Mailing list: https://launchpad.net/~nova >> Post to : [email protected] >> Unsubscribe : https://launchpad.net/~nova >> More help : https://help.launchpad.net/ListHelp >> >> Confidentiality Notice: This e-mail message (including any attached or >> embedded documents) is intended for the exclusive and confidential use of >> the >> individual or entity to which this message is addressed, and unless >> otherwise >> expressly indicated, is confidential and privileged information of >> Rackspace. >> Any dissemination, distribution or copying of the enclosed material is >> prohibited. >> If you receive this transmission in error, please notify us immediately by >> e-mail >> at [email protected], and delete the original message. >> Your cooperation is appreciated. > >> _______________________________________________ >> Mailing list: https://launchpad.net/~nova >> Post to : [email protected] >> Unsubscribe : https://launchpad.net/~nova >> More help : https://help.launchpad.net/ListHelp > > > _______________________________________________ > Mailing list: https://launchpad.net/~nova > Post to : [email protected] > Unsubscribe : https://launchpad.net/~nova > More help : https://help.launchpad.net/ListHelp >
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