I'm not offering an opinion for or against the decision to drop XMPP, but I wanted to offer some corrections to what is being said.
I think you've misunderstood how scale works. At scale, problems do not shrink, they grow.
I do not work on anything even closely related to Hangouts, but I used to run an ejabberd server myself, and I've worked with SIP a bit.
XML does have problems, both with bandwidth, (even compressed), high CPU utilization, parsing code is more complex (which leads to more security issues). XMPP also has issues, and I'm not just talking about how hard it is to get multiple Audio/Video clients to communicate[1]. (e.g. kernel resources, the incredible number of failure states, etc.)
Cheers, Doug
#1 At least early versions of iChat used XMPP with SIP. For those who don't know SIP, it stands for Session Initiation Protocol, which means that it doesn't transfer the audio/video, it's just a language for making connections. You have to negotiate a transport layer (which was often but not always RTP or SRTP). You have to exchange connection ports via SDP. If you're lucky and manage to get by all firewalls at this point, you now have to hope you're able to use compatible codecs. Interoperability was a nightmare.
The client-server protocol was simply JSON. XMPP was not involved. (Well, we translated protobuf messages to JSON, so it was ugly JSON, but still JSON).
we translated protobuf messages to JSON
aside, any opinions on others choosing that as a standard way of communicating between internal services on disparate runtimes? (golang<->python, for example)
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I think they meant the scale of Google (total) compared to the scale of just messaging.
i.e: If you could spend a year's worth of working cutting the costs of <sevice X> by 30%, that would be fairly meaningless if it was .000001% of the total cost of operation.
I don't know what Google's operating expenses are[1], but I'll use the public income numbers as a proxy, and you can adjust from there.
If you look at Google's first quarter 2013 numbers, they pulled in 13.97 billion in revenue, and I'll subtract the 2.96 billion in traffic acquisition costs to come up with 11.01 billion. We'll multiply by four[2] to get a rough estimate of yearly income: 44.04 billion.
If we assume that messaging is millionth of a percent = one hundred millionth[3] of Google's expenses, then the total cost to google is $440 per year, so saving 30% just doesn't make sense.
If, however, it's one hundred thousandth of Google's expenses (still a ridiculously small amount), then you're talking about $440k of yearly expenses, and you now need to compare a year of salary to 30%, or $146k.
At this point, depending on the availability of engineers (whether or not you have to factor in hiring costs) it starts to make a lot more sense.
Cheers, Doug
#1 and I probably wouldn't be able to divulge them if I did. :-)
#2 Each quarter is different, but x4 is a good rough estimate.
#3 Your numbers.
Now, XML itself is one problem, but the "culture" (eg, usage norms) around XML is another -- much like Java's cultural preoccupation with abstraction and boilerplate, XML-based formats have a tendency to veer towards the unwieldy and verbose. XMPP is no exception.
While XMPP has been instrumental in propagating standardized presence and IM, its age is showing. Unless we develop a modern, open replacement that is natively suited to the needs of today's Internet (voice, video, file transfer, group messaging, etc+), we will see companies continue to develop proprietary solutions that are locked behind walled gardens.
+XEPs and extensions are insufficient; too many optional extensions hinders interop and contorts the system beyond its original design specifications. Just ask anyone who's tried to implement chat/buddylists on top of SIP presence.
Youtube alone makes up a significant amount of the Internet's total traffic. Sending compressed XML isn't a problem for Google.
Sure, the page has really become a one-page app with some advantages that come from pre-loading, but jeez, it is still 1MB!
Then why comment? If you have nothing to input from either side. Doubt is not a valuable commodity.
Some of us need our thoughts clarified by the community.
In any case, I find that learning happens in an atmosphere of uncertainty, humility and exploration. Doubt, thus, is a valuable commodity in any community which encourages learning, and I'd like to believe HN is one of them.
If you respect people, then their opinions tell you things about the search space in which they live. Heck, even if you don't respect people it at least tells you nsomething about how widely known a particular thing is within comparable sections of society.
There are, potentially, some good arguments for filtering your information to keep newbies out of higher level discussion where people are trying to make progress on a problem - but in the context here it seems to me at the moment that you're just being somewhat mean; I don't see what you hope to gain other than to make someone feel bad.
Maybe you should refrain from commenting until you have something "valuable" to offer, too.
Optimizing parsing cost, at the expense of breaking foundational philosophy of their communication services, is hardly justifiable. XMPP has several overheads, XML will not top that list.
I hate XML as much as the next guy, but for a phone that can do 20 fps OpenGL scene the cost of parsing XML that is most certainly valid and as used by XMPP is effectively nothing.
Don't be a dick.
> for a phone that can do 20 fps OpenGL...
It's not just the phone, there is server overhead too, which everyone seems to be ignoring. While XML has a lot of problems, I never said it was the problem with XMPP (although it certainly isn't helping).
> Don't be a dick.
Oh, puh-lease.
> there is server overhead too
It's all going over the SSL, remember?
I have a life-long passionate hate towards XML, but you have to look at a larger picture to understand why Google is killing XMPP support. It's not the performance, it's not the lack of the protocol elegance. It's the fact that they are building a wall. Facebook got their herd walled and it seems to be working well for them, so it's only natural Google is doing the same. The XMPP was in a way, so it's gotta go.
But NIH/control is an unlikely reason for brewing their own protocol. If they simply wanted a wall, they could just disable federation. They've done it before, and it's working for WhatsApp, it's working for Facebook, it's working for Microsoft [1].
G already has a lot of experience with XMPP and it's probably just the engineering reality between what they want to accomplish with Hangouts and what it would take to retrofit XMPP or an existing protocol. Throwing out the baby with the bathwater? Maybe. But it wouldn't be the first time, and won't be the last.
[1] Remember that FBChat, Lync etc are internally proprietary, but they do expose XMPP gateways. Intentionally preventing federation is shitty, but dropping XMPP at the core is not.
[1] https://developers.google.com/talk/open_communications#devel...
[2] http://xmpp.org/extensions/xep-0138.html