Multi-Region Latency Based Routing now Available for AWS

http://aws.typepad.com/aws/2012/03/latency-based-multi-region-routing-now-available-for-aws.html

by jeffbarr • 14 years ago

89 36 14 years ago

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donavanm3• 14 years ago

I created a quick demo at http://region.strewth.org/ and a introspective TXT record at region.strewth.org. More details http://www.strewth.org/words/.

ryanbales3• 14 years ago

I am utterly floored by the frequency at which new features are being released for AWS... Are you Amazon people getting any sleep?

InclinedPlane• 14 years ago

They've been growing and hiring like crazy for the last 2 years or so.

pzb• 14 years ago

Yes, we sleep.

Come join us and be part of the fun that is AWS: http://aws.amazon.com/careers/

If you can name it, we are probably hiring for it.

jeffbarr2• 14 years ago

Five hours does it for me. And I have to write all of those posts!

As one of my colleagues mentioned, we are hiring (currently 516 open jobs on the AWS team). Here's a list that's easier to read:

http://awsmedia.s3.amazonaws.com/jobs/all_aws_jobs_list.html

jedberg• 14 years ago

And if you want to consume the fruits of their labor, Netflix is hiring too! http://jobs.netflix.com/

(Sorry Jeff, I couldn't resist)

sargun• 14 years ago

This has been one feature that I've been waiting for a while for a while. Otherwise, multi-region load balancing had to be done in the application, via geo-IP, or a third-party provider.

The only thing I'm curious as to is what kind of measurements is Amazon gathering, and how is it gathering them? Is it using ELB, and looking at TCP latency (delta time between SYN/ACK? Curious minds want to know...

gibybo• 14 years ago

So I'm a little fuzzy on how DNS works and this seems like a good place to ask:

I was under the impression that end users typically talked to DNS cache servers rather than directly to the authoritative servers in the domain's registration. If that's true, how can AWS provide different records based on the requesting user?

If end users are talking directly to one of the ~4 authoritative name servers listed in the registration, how does that scale to billions of queries?

electrum• 14 years ago

The caching servers are typically close to the user: at your ISP, in your office's server closet, in your data center, etc. In the case of public recursive DNS providers such as OpenDNS and Google Public DNS, this requires a recent extension to DNS: http://arstechnica.com/telecom/news/2011/08/opendns-and-goog...

mcpherrinm• 14 years ago

The most important thing going on here is Anycast. See http://en.wikipedia.org/wiki/Anycast for a complete description, but basically, multiple machines have the same IP address, and different routes are advertised to different networks. This results in packets being routed to the nearest DNS server.

Then, that DNS server can decide where the other end is and provide them with the correct IP.

You're right that most users use a caching DNS server, so it is actually the location of the DNS caching server. Of course, since most users choose a DNS server close to them (usually, their ISP), this should still result in a correct approximation. If you're using, say, 8.8.8.8 (google public dns), that's (probably) more than 1 server -- you're using the closest one to you. So then AWS will provide you with the closest AWS region to the closest Google DNS server, which is hopefully the closest one to you.

isb• 14 years ago

As mcpherrinm described, anycast plays a big part in how queries are routed to a DNS server in Route 53's global fleet.

You are right that a DNS server sees the query coming from the resolver instead of the user. So how does it pick the region closest to the user? As the blog post describes, we measure latencies from client networks to AWS regions and we also have a mapping of which resolvers are used by which client networks. If you put both of them together, you can compute which region is closest to the users of the resolver.

donavanm3• 14 years ago

> The most important thing going on here is Anycast. ... This results in packets being routed to the nearest DNS server.

Nearest in terms of AS path. This can be wildly different than latency as BGP isn't really implemented with cost/performance in mind. Anyone relying on anycast to answer their latency story is doing a lazy/poor/ignorant job of it.

> You're right that most users use a caching DNS server, so it is actually the location of the DNS caching server.

And another case where end users would be better served by providers implementing edns client-subnet extensions. This would allow savvy content providers to route to the actual end user, and not their resolver.

nl3• 14 years ago

Anycast is good in the absence of better options, but I don't think this is Anycast.

It sounds like here Amazon is doing unicast DNS, but dynamically changing the response depending on the IP address the query comes from.

Since they have a big database of IP addresses and latency, they can choose the best response.

The missing thing here is that they don't get the IP address of the client computer, only the DNS server. In many cases that (along with geo-location of the DNS Server) might be enough, but it is possible to do better. I'd speculate what they do here is correlate the IP addresses with the DNS server either by subnet or by using active measurement techniques.

ez773• 14 years ago

Sorry for bringing this off-topic issue on AWS: is it possible to set hard caps on monthly spending in AWS? I just asked this [1] but didn't receive a single upvote =S. Thanks.

[1] http://news.ycombinator.com/item?id=3737595

ryanbales3• 14 years ago

No. Just keep an eye on it.. it's cheap :p

esrauch2• 14 years ago

Except if you go on vacation to unplug for a week and had some bug or misconfiguration couldn't you easily run up a bill in the hundreds or thousands when you expect it to be in the tens?

If this is so implausible then why can't they provide a cap? It feels to me that they are purposefully trying to capitalize on people's mistakes. Call me paranoid but it is honestly the primary reason why I've been wary to play with AWS.

marquis• 14 years ago

You could set your own cap by monitoring on your server, and shut down services as needed. Maybe a new startup idea here for someone? We monitor our bandwidth here, and while we haven't had to deactivate services it's something we're prepared for.

donavanm3• 14 years ago

No, AFAIk AWS does not have the ability to restrict usage based on expenditure. There are startups that do this though, check http://www.enstratus.com/.

jeffbarr2• 14 years ago

That feature is currently in beta for our Premium Support customers. Here's a third-party blog post with more information:

http://blog.bitnami.org/2011/12/monitor-your-estimated-aws-c...

ez773• 14 years ago

Update for those interested: it looks [1] like it'll never happen...

[1] https://forums.aws.amazon.com/thread.jspa?messageID=249000

kogir2• 14 years ago

Amazon is such a tease. Just give us Anycast Elastic IPs that work in multiple regions already!

There's still no good high-availability story for region-wide outages, and there won't be until they do this.

mrkurt• 14 years ago

Anycast IPs would be lovely, but they're tweaky enough to use that I suspect the support burden would be high (since they suck for long lived connections). And they're not nearly as easy to provision as a complicated DNS setup.

They need to just stop having region wide outages...

jscott11• 14 years ago

Seems unlikely. Not every AWS user is in every region. They would need to have a separate range of anycast IPs for every possible combination of regions (2^N possibilities) to prevent packets from going into a black hole. If they wanted to be able to serve a conservative number of hosts in every region (say 32768) that would require 15-bits of IP space per combination. If AWS expands to 10 regions, that means 25-bits of the IPv4 space. A /8 only gives you 24.

I guess an alternative might be to do some kind of NAT for unbound anycast addresses which forwards packets to an available region, but that is hugely complicated.

kogir2• 14 years ago

I'd be delighted if they offered it for even just two regions. Right now if you want your service to be highly available you either run your own routers in two collocation facilities and forward to AWS, or you don't use AWS.

Multi-Region Latency Based Routing now Available for AWS

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