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phpmysqlsslnginxload-balancing
Katai
Katai

Reputation: 2937

Load Balancing - How to set it up correctly?

Here it gets a little complicated. I'm in the last few months to finish a larger Webbased Project, and since I'm trying to keep the budget low (and learn some stuff myself) I'm not touching an Issue that I never touched before: load balancing with NGINX, and scalability for the future.

The setup is the following: 1 Web server 1 Database server 1 File server (also used to store backups)

Using PHP 5.4< over fastCGI

Now, all those servers should be 'scalable' - in the sense that I can add a new File Server, if the Free Disk Space is getting low, or a new Web Server if I need to handle more requests than expected.

Another thing is: I would like to do everything over one domain, so that the access to differend backend servers isnt really noticed in the frontend (some backend servers are basically called via subdomain - for example: the fileserver, over 'http://file.myserver.com/...' where a load balancing only between the file servers happens)

  1. Do I need an additional, separate Server for load balancing? Or can I just use one of the web servers? If yes:
    • How much power (CPU / RAM) do I require for such a load-balancing server? Does it have to be the same like the webserver, or is it enough to have a 'lighter' server for that?
    • Does the 'load balancing' server have to be scalable too? Will I need more than one if there are too many requests?
  2. How exactly does the whole load balancing work anyway? What I mean:
    • I've seen many entries stating, that there are some problems like session handling / synchronisation on load balanced systems. I could find 2 Solutions that maybe would fit my needs: Either the user is always directed to the same machine, or the data is stored inside a databse. But with the second, I basically would have to rebuild parts of the $_SESSION functionality PHP already has, right? (How do I know what user gets wich session, are cookies really enough?)
    • What problems do I have to expect, except the unsynchronized sessions?
  3. Write scalable code - that's a sentence I read a lot. But in terms of PHP, for example, what does it really mean? Usually, the whole calculations for one user happens on one server only (the one where NGINX redirected the user at) - so how can PHP itself be scalable, since it's not actually redirected by NGINX?
  4. Are different 'load balancing' pools possible? What I mean is, that all fileservers are in a 'pool' and all web servers are in a 'pool' and basically, if you request an image on a fileserver that has too much to do, it redirects to a less busy fileserver
  5. SSL - I'll only need one certificate for the balance loading server, right? Since the data always goes back over the load balancing server - or how exactly does that work?

I know it's a huge question - basically, I'm really just searching for some advices / and a bit of a helping hand, I'm a bit lost in the whole thing. I can read snippets that partially answer the above questions, but really 'doing' it is completly another thing. So I already know that there wont be a clear, definitive answer, but maybe some experiences.

The end target is to be easily scalable in the future, and already plan for it ahead (and even buy stuff like the load balancer server) in time.

Upvotes: 1

Views: 440

Answers (1)

Volodymyr Smotesko
Volodymyr Smotesko

Reputation: 438

You can use one of web servers for load balacing. But it'll be more reliable to set the balacing on a separate machine. If your web servers responds not very quickly and you're getting many requests then load balancer will set the requests in the queue. For the big queue you need a sufficient amount of RAM.

You don't generally need to scale a load balancer.

Alternatively, you can create two or more A (address) records for your domain, each pointing to different web server's address. It'll give you a 'DNS load-balancing' without a balancing server. Consider this option.

Upvotes: 1

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