We have a website which provides services for people based in particular city.
We want to scale and provide it for more cities but we want to remain separated IT within the city realm: one webhost, cloud service , database etc for one location. It does not only enables us to scale individually (some cities are bigger than other several times) but most significantly it improves our code-base and db queries to not use city's predicates - despite the fact it is more expensive in general.
At the same time we do not want to use subdomain. User can switch city through dropdown and request should go to appropriate VM without url being changed so the routing should work seamlessly.
Based on Azure documentation we are still not sure what solution would meet our needs, Traffic Manager, Load balancer or custom redirects.
How you accomplish this is ultimately up to you, but from an Azure-specific perspective, the only multi-region built-in load-balancing service is Traffic Manager. This operates in one of three routing modes:
Primary/failover
Round-robin
Closest (based on latency, not physical distance)
For any other type of routing (such as letting the user choose location, per your question), you'd need to implement this on your own or via 3rd-party service (and how to accomplish that would be a matter of opinion/debate/discussion, which is off-topic for StackOverflow).
Since you're looking to have a separate DB, cloud-role and webhost per city, I do not see how you can get away from doing subdomains.
Do you not want subdomains because of SEO? If so, it'd be easier to find another way to solve SEO problem.
But whatever Traffic Manager or other DNS based routing solution you use, it'll be splitting users by where they come FROM and not where they're going TO.
The destination problem is solved thru separate sub-domains
Related
I have an azure traffic manager configured to route traffic over two data centres based on performance (latency). The two DCs are replicas of each other, and is engineered in this way so that our global customers are givin a good performance no matter where they are connecting from.
The application tiers do not hold state, and the data tiers are set up using SQL merge replication on a 1 minute timer to keep the DBS in sync as to provide service continuity in the event of a Datacenter failover.
The issues that I have found is that the traffic managers routing is slightly erratic. I have observed registering a user under one Datacenter only to find the login has bee routed to the other one - the SQL replication hasn't synced at this point and the second DC isn't aware that the user exists. Even though the user both registered and logged in from the same location! The DCs are in the West US and South east asia.
I'm looking at a few options to fix this. Solution A is to Silo the users data to a specific data center, therefor whatever DC the user registers to is used thereafter. I wouldn't have syncing issues but I lose the advantage of continuity that the SQL replication provides.
Solution B is to use a different more predictable global load balancer. But first I want some opinions and to perhaps see if I am doing something wrong or perhaps my architecture is flawed.
Thanks for advice.
My solution had challenges using the traffic manager also, although slightly different to yours. The traffic manager is a great value solution if it can work for you. As far as I am aware no configuration in traffic manager allows it to be aware of sessions, therefore it is blinkered to its config setting of performance in your case. This means its acting erratic based on your expectation for it to use sessions to be persistent to an endpoint subject to it being available.
In terms of your solution, it is very much Enterprise. To move backwards with solution A probably doesn't fit the requirement given what you went to the effort of building. Solution B brings many more features that Traffic Manager lacks and one of them will resolve your issue. For other reasons I am looking at
http://kemptechnologies.com/uk/server-load-balancing-appliances/virtual-loadbalancer/loadmaster-azure
It is designed for Azure and is available as a pre-installed VM. There are others available but this has been my choice and what I would use if I were in your position and wanted to keep the level of resilience you currently have.
Hope this helps.
We're developing a client-server game that communicates with our server in real time. During development we directed the client to the server's IP address directly.
Moving forward to release, we'd like to switch the target server IP to a domain name.
I'm looking for feedback whether we should use a sub-domain within our web-site main domain (say: server.mygame.com), or, setup a different domain for the game server (mygame-server.com).
If there is no difference either way I'd love to get feedback on that as well.
Thanks!
This question might be better asked at serverfault.com because it is not strictly related to programming...
Anyway, providing my opinion on your quesion: I'd go for a subdomain of a new game-related main domain.
Here's why: this should give you the most flexability for future changes, assuming the following thoughts:
A new domain especially for that game allows you to promote game information on the www. subdomain.
The game endpoint sits (for example) at api. which points to a different server than any of the websites (improves stability, allows different software for same ports, e.g. web servers).
You can add round-robin DNS load balancing (or any other load-balancing) later. This might be easier if this can be done on a spearate main domain.
You don't have to mess with the main company DNS entries for any game-related settings, improving the stability of both services (as they are separated).
If you might sell the game one day, and a different domain makes it easier to transfer all services and data.
Using a subdomain makes it easier in general because normally the second-level domains (like the A record for example.com) is handled by the DNS servers at a "lower" level in "DNS authority tree" (e.g. at you DNS provider), so it might be more difficult to add special features like load-balancing there.
So these are only some thoughts. Basically it should not matter which way you set up the DNS entries, but if one of the topics above applies (or otherwise sounds reasonable) then you might choose a subdomain on a new domain ;)
Normally, we restrict access to our website from certain countries at the edge of our network. We are about to deploy our application to Azure and need to block certain countries from accessing it. This is due to U.S. Embargo policies... What is the best way to block certain countries so we meet U.S. laws and regulations?
Thanks,
Mike
One idea is to build a simple proxy that attempts to filter on region. My teammate Ricardo Villalobos co-wrote an MSDN article explaining how someone might do that with node.js, in Azure, filtering against the MaxMind geolocation database. It's probably not an exact fit, as it deals with media stream filtering, but you should be able to use the basic technique and proxy described, as a starting point.
I have seen on the web some domain names having prefix of ww2 or ww3 or so (ww2.somedomain.example, ww3.yourdomain.example). And these happen mostly when traveling from a page to page. What would be the reason of having such subdomains? Is there anything special about them or are they just another sub domain? I mean, are they useful in any particular context?
People running large(-ish) sites used to do this when they needed to break up the load between more than one server. One machine would be called www then the next one would be called www2, etc.
Today, much better load balancing solutions are available that don't require you to expose your internal machine naming conventions to the browser clients.
Technically, the initials before the primary domain name (e.g. the "mail" in mail.yahoo.com) can be best though of as a machine name, identifying the web server/mail server, whatever. They can also identify a group of machines (a web farm).
So the person building up that machine can call it anything they want. The initials www are a (somewhat arbitrary) convention.
Oftentimes, ww{x} is used to indicate a particular server of a set of mirrored servers. If properly configured, I could have www.mydomain.example point to my web site on a load balancer, while I could use ww1, ww2, ww3, etc to access the site guaranteed from a specific LBed server.
I can see 3 possibilities
make the browser load resources more faster. the browser would open a fixed number of connection to same domain not to load the server
they are using more then one server so they can share the load between servers
separate some content to a separate virtual host or server. some kind of organization ...
As various answers have pointed out, modern day load-balancers can balance load without having to resort to using different sub-domains for each machine. However, there is still one benefit of dividing your site into various sub-domains: maximize browser connections.
All browsers limit the number of concurrent connections to a particular host (6 for most modern browsers). If a page contains lots of assets, page-load would be slow as the browser queue those requests because of connection limit. By loading different assets from different subdomain, you get around the connection limit, speeding up page-load.
Typically it's a partitioning strategy. When sites get sufficiently large that they can't run (or run well) on a single server you then have to look at solutions for scaling the application out horizontally (ie more servers) rather than vertically (ie bigger servers).
Some example partitioning strategies are:
Certain users always use certain servers. This can be arbitrary or based on some criteria (user type, geographic location, etc);
When a user gets a session that session is assigned to a particular server (sometimes called "sticky sessions" although this can also be used where such different machines are transparent); and
Certain activities are always on certain machines.
Another common case is organizational reasons. In an extremely large company, www might be for their main marketing website. And, ww2 might be, say, for product documentation pages.
In an ideal world, all departments would share perfectly. In practise, a big company might have their (www) marketing pages managed by an external agency. Their internal (ww2) pages done by their internal team. Often, the marketing agency just doesn't update pages quickly or refuses to run certain stacks, may be too limiting in terms of bureaucratic needs.
The marketing agency may insist on controlling the www and not sharing due to past situations where a company website went down due to internal reasons and yet the agency got blamed, or vice versa.
So, theoretically, there's no need to do this with modern load balancing and such. But, in practise, it can be a lot cheaper, straightforward and allow better business productivity.
I'm interested in cross-colo fail-over strategies for web applications, such that if the main site fails users seamlessly land at the fail-over site in another colo.
The application side of things looks to be mostly figured out with a master-slave database setup between the colos and services designed to recover and be able to pick up mid-stream. I'm trying to figure out the strategy for moving traffic from the main site to the fail-over site. DNS failover, even with low TTLs, seems to carry a fair bit of latency.
What strategies would you recommend for quickly moving traffic between colos, assuming the servers at the main colo are unreachable?
If you have other interesting experience / words of wisdom about cross-colo failover I'd love to hear those as well.
DNS based mechanisms are troublesome, even if you put low TTLs in your zone files.
The reason for this is that many applications (e.g. MSIE) maintain their own caches which ignore the TTL. Other software will do a single gethostbyname() or equivalent call and store the result until the program is restarted.
Worse still, many ISPs' recursive DNS servers are known to ignore TTLs below their own preferred minimum and impose their own higher TTLs.
Ultimately if the site is to run from both data centers without changing its IP address then you need to look at arrangements for "Multihoming" via global BGP4 route announcements.
With multihoming you need to get at least a /24 netblock of "provider independent" (aka "PI") IP address space, and then have that only be announced to the global routing table from the backup site if the main site goes offline.
As for DNS, I like to reference, "Why DNS Based Global Server Load Balancing Doesn't Work". For everything else -- use BGP.
Designing networks in order to load balance using BGP is still not an easy task and I myself certainly am not an expert on this. It's also more complex than Wikipedia can tell you but there are a couple interesting articles on the web that detail how it can be done:
Load Balancing In BGP Networks
Load Sharing in Single and Multi homed environments
There is always more if you search for BGP and load balancing. There are also a couple whitepapers on the net which describe how Akamai does their global loadbalancing (I believe it's BGP too.), which is always interesting to read and learn about.
Beyond the obvious concepts you can use software and hardware to achieve, you might also want to check with your ISP/provider/colo if they can set you up.
Also, no offense in regard to your choice of colo (Who's the provider?), but most places should be setup to deal with downtimes and so on, they should not require you to take actions. Of course floods or aliens can always strike, but in that case I guess there are more important issues. :-)
If you can, Multicast - http://en.wikipedia.org/wiki/Multicast or AnyCast - http://en.wikipedia.org/wiki/Anycast