Rails app with multiple subdomains on separate machines

Question

I've got a Rails application that has 3 main parts:

• www.example.com: This is the main website
• api.example.com: The API
• dashboard.example.com: The dashboard interface for signed up users

I've currently got them setup in a single rails app with namespaces, and share models. I recently got accepted on the RackSpace startup program which gives me $2000 (!) worth of FREE cloud storage each month so I thought I'd distribute the app up into smaller pieces, so that the subdomains are hosted on separate servers.

How can I do that without deploying the same code to 3 different servers? I reviewed this related question, but it seemed to imply using a single Git repo for all three "projects" and I wasn't sure how that could would get deployed.

Answer 1

There are two very different goals intertwined here:

One is distributing the load over multiples machines. You don't need to break out your application into multiple apps for that. You could use a load balancer for this (incoming requests are spread across multiple machines running the same app), or split your app up.

The other is more about the logical architecture of your app. In general the bigger an app is, the more complicated it is and it's easier to work on simple apps. Therefore you might want to split your app up into smaller apps. This is orthogonal to the hardware issue - you could choose to split your app up threeways but still run them on the same machine (it does of course give you the flexibility to allocate resources differently to your app)

Coming back to you question, one aspect worth exploring is should there be any shared models? To what extent can (for example) your dashboard query your api (possibly private apis) rather than querying the database directly? Splitting up your application into multiple services makes some things easier, some things harder, but it does help you keep individual applications smaller and keep the boundaries between them clean without any hidden dependencies. This logical split doesn't have to correspond the the physical layout: one server may host several applications

Lastly the most direct answer to your question is to write a rails engine. An engine can contain pretty much anything an app can (applications are special cases of engines), for example models, views, controllers routes etc. You'd create one with your common code, package this up as a gem (doesn't have to be a public one) and add it each app's Gemfile.

Answer 2

Load Balancer

For lack of more experience, I would say what my gut is telling me - simply, you don't need any more servers (unless of course you have massive throughput)

You may be better putting this on the SuperUser community or something - I personally believe you'll be better with a load balancer (although I've never used one before), to give you the capacity to spread the load of your apps across mulitple server instances.

Quite how this will work is beyond me (I've never had to use one), but I would certainly look at that far quicker than trying to split your app between servers:

Load balancing is a computer networking method for distributing workloads across multiple computing resources, such as computers, a computer cluster, network links, central processing units or disk drives. Load balancing aims to optimize resource use, maximize throughput, minimize response time, and avoid overload of any one of the resources. Using multiple components with load balancing instead of a single component may increase reliability through redundancy.

Load balancing is usually provided by dedicated software or hardware, such as a multilayer switch or a Domain Name System server process. Load balancing is differentiated from channel bonding in that load balancing divides traffic between network interfaces on per network socket (OSI model layer 4) basis, while channel bonding implies a division of traffic between physical interfaces at a lower level, either per packet (OSI model Layer 3) or an data link (OSI model Layer 2) basis.