On Tue, Sep 23, 2014 at 9:13 AM, Zane Bitter <zbit...@redhat.com> wrote:
> On 22/09/14 22:04, Joe Gordon wrote: > >> To me this is less about valid or invalid choices. The Zaqar team is >> comparing Zaqar to SQS, but after digging into the two of them, zaqar >> barely looks like SQS. Zaqar doesn't guarantee what IMHO is the most >> important parts of SQS: the message will be delivered and will never be >> lost by SQS. >> > > I agree that this is the most important feature. Happily, Flavio has > clarified this in his other thread[1]: > > *Zaqar's vision is to provide a cross-cloud interoperable, > fully-reliable messaging service at scale that is both, easy and not > invasive, for deployers and users.* > > ... > > Zaqar aims to be a fully-reliable service, therefore messages should > never be lost under any circumstances except for when the message's > expiration time (ttl) is reached > > So Zaqar _will_ guarantee reliable delivery. > > Zaqar doesn't have the same scaling properties as SQS. >> > > This is true. (That's not to say it won't scale, but it doesn't scale in > exactly the same way that SQS does because it has a different architecture.) > > It appears that the main reason for this is the ordering guarantee, which > was introduced in response to feedback from users. So this is clearly a > different design choice: SQS chose reliability plus effectively infinite > scalability, while Zaqar chose reliability plus FIFO. It's not feasible to > satisfy all three simultaneously, so the options are: > > 1) Implement two separate modes and allow the user to decide > 2) Continue to choose FIFO over infinite scalability > 3) Drop FIFO and choose infinite scalability instead > > This is one of the key points on which we need to get buy-in from the > community on selecting one of these as the long-term strategy. > > Zaqar is aiming for low latency per message, SQS doesn't appear to be. >> > > I've seen no evidence that Zaqar is actually aiming for that. There are > waaay lower-latency ways to implement messaging if you don't care about > durability (you wouldn't do store-and-forward, for a start). If you see a > lot of talk about low latency, it's probably because for a long time people > insisted on comparing Zaqar to RabbitMQ instead of SQS. > I thought this was why Zaqar uses Falcon and not Pecan/WSME? "For an application like Marconi where throughput and latency is of paramount importance, I recommend Falcon over Pecan." https://wiki.openstack.org/wiki/Zaqar/pecan-evaluation#Recommendation Yes that statement mentions throughput as well, but it does mention latency as well. > > (Let's also be careful not to talk about high latency as if it were a > virtue in itself; it's simply something we would happily trade off for > other properties. Zaqar _is_ making that trade-off.) > > So if Zaqar isn't SQS what is Zaqar and why should I use it? >> > > If you are a small-to-medium user of an SQS-like service, Zaqar is like > SQS but better because not only does it never lose your messages but they > always arrive in order, and you have the option to fan them out to multiple > subscribers. If you are a very large user along one particular dimension (I > believe it's number of messages delivered from a single queue, but probably > Gordon will correct me :D) then Zaqar may not _yet_ have a good story for > you. > > cheers, > Zane. > > [1] http://lists.openstack.org/pipermail/openstack-dev/2014- > September/046809.html > > > _______________________________________________ > OpenStack-dev mailing list > OpenStack-dev@lists.openstack.org > http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev >
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