How to start with load balancers ?
All of us playing with load balancers started the same way. First you prepare a configuration to alternate between two web servers returning different contents, and you verify with your browser that you indeed get a different response on each reload. This is the most basic load balancing setup one can imagine (and the worst one at the same time). Then you start all these “what if” questions. “What if a server dies”. You manage to address this by enabling health checks., but you feel like you’re cheating when you stop the server by killing the process. “What if now the cable is pulled off while transfering data”. This becomes difficult, you need to start a VM and you’re not completely sure you model the proper failure by stopping the VM, maybe the hypervisor will send some resets or ICMP messages. Then “What if I the load balancer itself fails”. Cheating with VMs that are started and stopped by hand doesn’t make you feel comfortable in that what you’re doing will work in real production. “What if someone by mistake configures two servers with the same IP address”. “What if I enable VRRP to cover hardware failures and my checks are wrong and I end up with two masters”. “What if I provoke a multicast loop”. “What if I setup multiple VRRP instances in multiple VLANs”.
All of these questions may sound very advanced to newcomers but are in fact quite common. In the world of load balancing, you definitely need to imagine a lot of failure cases and how to deal with them. Playing with pure software helps understand the basic concepts. Playing with VMs helps going a little bit further and already becomes quite painful. Add VLANs to the mix, asymmetric routing, DSR, transparent proxying and you’re quickly screwed.
Most of us started by plugging and pulling off cables , both network and power supply. I personally tortured a lot of Alteon AD3 in 2000-2001, but I was extremely lucky to have access to a lab where there were plenty of them (and they were really great devices to learn load balancing by the way).
But since it remains the best way to learn the concepts and to develop skills, HAProxy Technologies wanted to offer this opportunity to beginners again.
What if you could set up a complete load balancing lab on your desk, at school or at home ?
The photo above shows a complete load balancing platform deployed on a desk, with real machines and a real switch. And it’s just an example of what can be achieved. In order to make this possible, we ported our flagship product, the ALOHA load balancer, to a miniature MIPS-based platform which forms the ALOHA Pocket. This platform is designed and built by maker GL-Inet and is originally a WiFi router. But it has quite decent specs (2 FastEthernet ports, a 400 MHz 32-bit CPU, 64 MB of RAM, 16 MB of flash, and powered over USB), which are quite sufficient to run an ALOHA, is very convenient to manipulate, is rock solid and it is affordable. So it’s perfect to mass-produce an ALOHA that we can send around the world to interested participants. For now we have enough in stock to cover several tens of projects, we may order new ones if the stock goes away too quickly.
With this ALOHA Pocket, our goal is very simple : we want to introduce more people to load balancing., because we believe the future is there (load balancing, application delivery, content switching, function chaining, call it as you want, all these concepts are tightly coupled). Thus we are willing to offer a couple of load balancers for free to any student or intern who can describe a project they are working on that involves load balancing, in exchange for their promise to regularly publish their progress, on a blog for example. We’re not going to verify who writes and when (though we welcome links), we bet that most participants will be honnest and will respect their engagement. We estimate that the more people who show what can be achieved using a load balancer, the more people will be attracted and will fall into that addiction in turn. It is even possible that some participants will face some bugs or will suggest improvements, we’re definitely willing to hear about this as well. Don’t be ashamed, suggest and criticize on your articles, we’re not asking people to send us flowers, just to be open! And maybe your comments will make some companies notice your skills and propose you a job after you finish your classes 🙂
This ALOHA Pocket is full-featured. It runs at quite a decent speed (around 450 connections per second with all features turned on, this is more than the vast majority of web sites). We could not put our anti-DDoS protection, PacketShield, in it because it requires more memory than this device contains. But we don’t consider that this is important for beginners. The devices will be shipped with the last version of our ALOHA platform, 8.0. We will intentionally not provide frequent software updates because we want to be sure that they will be used for educational purposes only and not to run production! But we’ll issue updates if users are facing bugs because we want them to learn in comfortable conditions.
Now, if you are interested, please send an email to contact at haproxy dot com with the subject “ALOHA Pocket”. Introduce yourself, what you intend to do (eg: load balance Apache/Nginx web servers, load balance Postfix mail servers, set up a cloud platform involving haproxy, design a CDN involving HAProxy and Varnish, etc). Please provide enough details so that we may advise you if we detect some well-known traps in what you’re describing. Please indicate in what context you’re going to do this (at school, at university, for a company), and where you’re going to publish your progress, We don’t ask you to publicly disclose on your blog the name of the organization you’re working for, we know that some large ones still have problems with this. Indicate an estimated time frame for your project, and of course your shipping address. Try to be descriptive, as we consider that people not willing to write a few lines to get two free load balancers do not even deserve a response. By the way, if you believe you already have a compatible hardware and you’d only need the software image and procedure to flash it, contact us as well, we’ll welcome your demand as it means more people will be able to get one.
For logistics reasons, we’re going to send them in batches, so they will take a bit of time to arrive. Please bear with us, we’re handling all this by hand and installing all of them ourselves, just because we believe that this project is cool.
Let’s hope you’ll have as much fun using it as we had creating it 🙂