How to run multiple tiny Ruby (Rack) apps on one server? - ruby-on-rails

I want to run several (more than 2) tiny Rack-based apps on my VPS, which already has one large Rails app running.
The Rails app uses the traditional pair of Unicorn & nginx, and it requires most of the RAM that I have on my VPS.
I've tried adding similar Unicorn configurations for each app and it led me to conclude the RAM is insufficient.
So my question is: is it possible to set up one small memory-saving server which allows me to run several Sinatra apps at once?
UPDATE: in case it matters, I don't care much about the performance. These apps are not intended to do any serious jobs.
UPDATE 2: an approach based on sockets shared with Nginx is preferred over the one with ports.
Thanks!

I did my own exploration of this question and I think I found a solution which will allow me having one web-server running all my tiny apps at once.
It is based on RackStack not-yet-a-gem created by Remi Taylor (#remi on Github) https://github.com/remi/rack-stack.
RackStack is inspired by Rack::Builder, which as well seems being good for accomplishing a task like this - RackStack just goes in the same direction further, abstracting "stack" functionality in a way I found very nice and handy.
Here is a demonstration of RackStack which consists of two sample apps (Sinatra and Rack): https://github.com/stanislaw/skeletons/tree/master/rack_stack. To mimic stack app behavior on a real server I modified my /etc/hosts file to have localhost2 host pointing to 127.0.0.1.
I fire up Thin server and then run requests on localhost or localhost2: the requests to 'localhost' are served by FirstApp, to 'localhost2' by SecondApp.
I can't now foresee any problems that can appear, when I will test my apps on a real server, but now this approach seems to be exactly what I was looking for: I imagine, that on a real server Nginx will pass requests to all the hosts associated with my rack apps to a socket listened by Thin server. So, RackStack will meet only those requests which are addressed to the apps I have in my stack.
Any suggestions, improvements of this scheme or alternatives are still appreciated!

Related

Is it necessary to use Nginx when deploy a Rails API ONLY app?

Currently I've already read a lot tutorials teaching about Rails App deployment, almost every one of them use Nginx or other alternatives like Apache to serve static pages. Also in this QA Why do we need nginx with thin on production setup? they said Nginx is used for load balancing.
I can understand the reasons mentioned above, but I write a Rails App as a pure API backend service, the only purpose is to serve JSON formatted data for other client-side apps, no pages rendering at all. So my questions are:
In my situation, do I really need Nginx just to deploy a pure API Rails App?
If not, how should I deploy my app? just running it (with unicorn in production env) at background is good enough? like rails server -e production -d?
I'm so curious about these two question, hope someone can explain the details or show me some good references for me, thanks in advance.
See basically, Unicorn or thin are all single threaded servers. Which in a way means they handle single requests at a time, using defering and other techniques.
For a production setup you would generally run many instances of unicorn or thin ( depending on your load etc ), you would need to load balance b/w those rails application server instances, thats why you need Nginx or something similar on top.
to serve JSON formatted data for other client-side apps, no pages rendering at all
You see, it makes no difference. These tasks are similar: format certain data into a specific text-based structure. Much like rendering a view in HAML, ERB or whatever.
The difference is, you won't be serving static assets. At least, it's not practical for pure JSON APIs.
If you aim for compact JSON responses, your best bet is Unicorn (several workers) + nginx.
Unicorn is simpler and aims for fast single-client response. That is, a slow client could force Unicorn to waste a lot of time serving him a response. When backed by nginx though, it fires the entire response into nginx's buffer and heads for the next one only waiting for nginx to accept the response (since it's usually on the same machine, it's blazing fast). nginx then hands out responses. There could possibly be multiple instances of Unicorn, if one is not enough: but using only one could eliminate any kinds of data races on app level (which are possible in multithreaded apps).
Thin is designed by itself to handle multiple clients concurrently by itself, through use of threads and workers. Keep in mind though that MRI ("classic" Ruby) doesn't have "truly concurrent threads" because of GIL. Technoligies it's based on (Ruby+C) make it inferior to nginx (pure C) in terms of resource usage efficiency. nginx is even used sometimes to counter DDoS attacks, efficiency is proven in the wild (<1> <2> <3> and many more).
You could benefit from Thin if your app implied concurrent service for multiple clients, like Server-Sent Events or WebSocket usage, that require maintaining a constant connection. This one doesn't seem to. Don't count on concurrency too much where it's not required.

Best web/app server to host multiple low hit rails/sinatra apps

I need to host a lot of simple rails/sinatra/padrino applications of different ruby versions each with 0..low hits per day. They belong to different owners and should be well isolated from each other.
When an app is hit it should respond in reasonably short time, but I expect several simultaneous visitors are hitting the same site to be a rare case.
I'm going to create separate os user for each application. Surely I'd like to put them as many per server as it's possible. Thus I need to choose the web server with the lowest memory footprint, which can run applications on behalf of different users with different ruby versions and gemsets.
I consider webrick,nginx+passenger,thin,apache+passenger. I suppose the reliability of all choices is sufficient for such a job, and while performance isn't an issue, the memory consumption is.
I found many posts regarding performance issues, but most of them discuss the performance tuning and issues. I couldn't find a comparison of web servers memory usage when idle.
Is "in process" webrick the best choice? Which one would you choose for that job?
And I couldn't figure out how to resolve subdomains to application ports with webrick. Shall I use nginx or apache for that?
I don't have much experience with hosting myself, but using Webrick for production is not a good idea I think. You can also check out mongrel which I saw used in production. In most cases though you will probably want to choose between thin and unicorn. Check out this http://cmelbye.github.com/2009/10/04/thin-vs-unicorn.html or google around. Good luck :-)
Why not use Heroku? Its free and gets you out of the hassle of server configuration and maintenance.

Selecting a Rails host [closed]

Closed. This question is opinion-based. It is not currently accepting answers.
Want to improve this question? Update the question so it can be answered with facts and citations by editing this post.
Closed 9 years ago.
Improve this question
I'm close to picking a Rails host. I think I need a VPS solution, because (1) my Rails app has gems and plugins that I need to install to get it working, and (2) I need an SMTP server to send emails from my rails app out to users.
But then it occured to today...
1) Do I actually need VPS and root access to get my app up and running, just because I need to install gems, or can I just copy my Rails app folder up to a Rails-supporting hosting server and start it?
2) If I get a Google Apps account, which would include a business-class GMail solution, would that give me an SMTP server which I could use to send emails to users?
I'm looking for least-support-needed-solution. I can afford to pay for VPS hosting, and a Google Apps account, but I just wonder if this is really my best option.
UPDATE: It's now been just over three years since I first posted this question and answer. I still prefer AWS for all new deployments of a professional or serious horsepower nature (that is, if I don't self-host), but I also regularly deploy demo and tutorial apps to Heroku. I haven't tried any of the many VPS providers that have popped up such as Linode or DigitalOcean, but generally hear good things about them.
The key thing that keeps me from choosing Heroku for all my apps is cost. Since most of my indie projects outside of work are things where I'd prefer to absolutely minimize costs, AWS remains the better deal between AWS vs. Heroku. AWS (or any VPS provider for that matter) has the nice side effect of teaching you the OS along the way, which turns out to be hugely valuable in the long term.
=======================
So, two years later, here's my update. I've used three services for hosting, and here's my take on each of them (I actually love them all, but for various reasons).
Slicehost (now part of Rackspace Cloud Hosting)
This was the first VPS host I tried, and I loved them. The people there were amazing, support was awesome, and it had a really cool grassroots kind of feel. Now that VPS as a solution is more mainstream, and Rackspace has long since purchased Slicehost, I feel that the service offering is still awesome. If you want a simple way to setup a server, plenty of Linux distro choices, and control over your server, this is an awesome option.
Heroku
Love these guys too. I built a hobby app that is hosted there, rpglogger.com (which as of Nov. 2012 has actually migrated to Amazon Web Services), and developing and deploying to Heroku is a no-brainer. I really like working on Heroku for two reasons:
It's dead simple to setup. It really is as easy as they say, in my experience, to get an app running on their platform.
A single dyno (web server instance) is free. So hobby apps, and smaller apps basically get free hosting. It's not just for hobbies though - their plugin architecture is second-to-none, making the addition of 3rd party plugins such as NewRelic, Exceptional, and anything else on their platform a matter of just a few clicks.
You absolutely cannot beat Heroku for ease of use. Deploying an updated version of your app is literally as simple as pushing to your git repo. Heroku isn't necessarily cheap (for anything other than the small app), but if you're in a situation where you believe developer time is more valuable than having control over the server, then this is an amazing option. You can always migrate your app to any other platform anyhow, if it gets big, or the needs of the app vs. the cost of Heroku no longer make sense for you.
Amazon Web Services
I do quite a few small apps, and AWS reserved instances are awesome. For $60 I can basically get a reserved instance for an entire year. That one server is enough to run 3-4 small apps on the same machine, with more optimized memory usage, and the ability to run multiple web server instances (vs. Heroku's one free dyno, though I hear you can custom config your Heroku dyno using unicorn to get more scalability). Basically, AWS scales really well, and lets you share a server among multiple small apps, or spread a larger app across multiple servers.
On top of that initial cost for the reserved instance, I only have to pay for bandwidth and other AWS usage (S3, for example). I think AWS is an amazing mix of ultimate scalability, great costs, ultimate control, and for enterprise customers who want to build their entire infrastructure in the sky, it can't be beat. Rackspace Cloud Hosting provides similar services, and they're probably comparable for most things. But if what you want is the Swiss army knife of cloud services, I think AWS is still way ahead of everyone else.
===============
So, that being said, I started on Slicehost, then went to AWS, then tried Heroku, and today I spend most of my time back on AWS.
AWS is the kind of platform that, after you invest a little time in setting up your collection of VPS machines, it often makes sense to stay on this platform and leverage their ever increasing set of tools.
Granted, it took me two years of trying several options, and trying every level of management from fully managed servers (i.e. Heroku, where you don't even think of the server, just the app) to fully controlled servers (Slicehost and AWS). After all that I've come to this point where I'm ready to manage my own machines in order to get the flexibility and low costs that I want.
Through automation, the actual management of the servers on AWS becomes a non-event, so I don't spend my time constantly patching my machines, or doing other sysadmin tasks. I just check periodically to see if my servers need reboots, I set them to automatically install all security updates (I happen to deploy to Ubuntu servers), which means I spend 99% of my time (at least day-to-day) writing the application - not managing the servers (managing services is instead an occasional task of a few day's work, and then nothing else for months) - which is where I want to spend my time as a developer.
Neither of your requirements are VPS-specific. I use shared hosting from Site5 and currently run two rails apps through the account, both with gems that are not installed on the server by default and sending email. Installing gems does not require root access.
If you want to use a VPS anyway, both Slicehost and Linode are often recommended for Rails apps. A few more are listed under Deploy on the Rails site. I would encourage you to do some research on your choice in either case. Good luck!
You could check out Ruby on Rails Hosting, What is a good Ruby on Rails hosting service?, Good Ruby on Rails free hosting, and What is a good Ruby on Rails and PHP hosting?.
I personally prefer Heroku which has offers free low-scale hosting and is very easily upgraded. Also, they allow you to install gems (similarly to the gem dependencies and rake gems:install, but with different syntax/files), and send a few free emails (200, but it is easily upgraded).
I hate Heroku, it gives you no control over services you want to use and it's massively over priced. Just try to make use of a gem or service they don't specifically support and you will quickly find the limitations and the horrendous pricing.
Heroku is my host of choice.
You can send messages using GMail SMTP as well as the commercial SMTP plugin.
I have also used Slicehost, Linode, Dreamhost and RailsMachine.
Slicehost/Linode are awesome if you can set up the box yourself.
Dreamhost is cheap-as and great for staging. Sites are ponderously slow at times though.
RailsMachine is second to none as a managed service. Highly recommended for the support and the well-tuned stack.
I prefer linode, aws or so.
linode : is a standard linux server. you can login, install 3rd party dependencies and play around just like in your own server. Installing nginx/rails/ruby is the same way as what you did on your own pc/laptop/server.
heroku : is a service. I have to learn lots of stuffs that are not valuable at all if one day you switch to another platform(e.g. linode) or you have your own real server, for example, check the logs, install databases, or install gems. I have printed out most of its documents and read them in 1/2 days, and then I realize that I can't use these knowledges in my working server( that my company offered to me)
linode is cheap enough, $20 per month.
heroku is not always free. and I don't think it's stable enough for demonstration purpose.(e.g. your free heroku app will fall in sleep in spare time, and will cost you several seconds to wake up. this SEVERAL seconds is long enough to make you lost your customers if they want FAST web app )
so, forget heroku, buy or setup your own VPS, use it for years, then you will be an linux expert.
I use HawkHost for all my hosting needs, and I'm 90% sure they meet all your criteria. They provide web hosting and VPS services for very good prices, and their basic web host plan lets you have Rails applications running as well.
I'm used Joyent host- http://www.joyent.com. It's good Rails host.

Recommendations for a snappy Ubuntu + Rails server

I run an Ubuntu 8.04 shared host (VMWare) with Apache + Passenger (= Mod Rails), MySQL and Acts_As_Ferret (in server mode). It's too slow at the first requests. I do a lot of REST operations on it and have very few users.
Now I want to do a fresh installation...
Which setup (based on Ubuntu) do you recommend for a really snappy RoR server? (e.g. Ngnix, Thin, Mongrels or other fancy stuff)
Passenger is slow at first requests because it is idling and it shuts down all the rails processes so the first request has to load a rails process. You need to either ping regularly to avoid it idling and closing rails processes or set the idle timeout to a high value.
Look in the documentation for RailsPoolIdleTime
Check the ec2onrails mailing list, where there has been a lot of discussion of the various thin/nginx/passenger/apache alternatives and permutations, plus some hard data posted based on some decent tests.
You'll also find a nice packaged RoR/Ubuntu stack in the shape of the ec2onrails image (google ec2onrails) - it's for running on the amazon EC2 cloud but it's got a lot of nice stuff in there + capistrano tasks. Currently it's based on apache, but the version in progress is looking at the alternatives. No reason you couldn't use the same build script for a non EC2 server.
If your problem is simply the initial requests, try warming your server up before considering it live (e.g. by running a script to automatically exercise the basic operations).
Oh and I should add - are you sure the problem is your stack? More likely it is your code. It may be worth seeing where your bottlenecks are first and what you can get out of caching, improved queries and indexing, and especially memcached before tweaking anything else.
Well you could get a big speed boost by switching to Ubuntu 9.04 or even 8.10
I personally use nginx+passenger on my ubuntu stack. and use sphinx instead of ferret as well

Recommendations (and Differences) between different Ruby on Rails Production Web Servers

Very soon I plan on deploying my first Ruby on Rails application to a production environment and I've even picked a webhost with all the managed server and Capistrano goodness you'd expect from a RoR provider.
The provider allows for Mongrel, Thin, Passenger & FastCGI web servers, which seems very flexible, but I honestly don't know the differences between them. I have looked into them some, but it all gets a bit much when they start talking about features and maximum simultaneous requests - and that this data seems to vary depending on who's publishing it.
I have looked at Passenger (on the surface) - which does seem very appealing to me - but I was under the impression that Passenger wasn't the actual webserver, and instead was more like a layer on top of Apache or nginx and managed spawned instances of the application (like a Mongrel cluster).
Can anyone please set me straight with the differences in layman's terms so as I can choose wisely (because anyone who's seen Indiana Jones and the Last Crusade knows what happens if you choose poorly).
Short answer
Go with Apache/Nginx + Passenger. Passenger is fast, reliable, easy to configure and deploy. Passenger has been adopted by a large number of big Rails applications, including Shopify.
(source: modrails.com)
The long answer
Forget about CGI and FastCGI. In the beginning there were no other alternatives so the only way to run Rails was using CGI or the faster browser FastCGI. Nowadays almost nobody runs Rails under CGI. The latest Rails versions no longer provides .cgi and .fcgi runners.
Mongrel has been a largely adopted solution, the best replacement for CGI and FCGI. Many sites still use Mongrel and Mongrel cluster, however Mongrel project is almost dead and many projects already moved to other solutions (mostly Passenger).
Also, a Mongrel based architecture is quite hard to configure because it needs a frontend proxy (thin, ngnix) and a backend architecture composed of multiple Mongrel instances.
Passenger has been gaining widespread attention since it was released. Many projects switched from Mongrel to Passenger for many reasons, including (but not limited to) easy deployment, maintainability and performance. Additionally, Passenger is now available for both Apache and Ngnix.
The simplest way to use Passenger is the Apache + Passenger configuration. One Apache installation and multiple Passenger processes.
If you need better performance and scalability, you can use Ngnix as a frontend proxy and forward all Rails requests to multiple backend servers, each one composed of Apache + Passenger.
I'm not going into the technical details here, this solution is intended to be used by Rails projects with an high level of traffic.
Even more complex solutions include a combination of different levels including http proxies and servers. You can have an idea of what I'm talking about reading some internal details from GitHub and Heroku.
Right now, Passenger is the best answer for most Rails projects.
Mongrel and Thin are single ruby process servers that you would run multiple of as a cluster behind some type of proxy (like Apache or Nginx). The proxy would manage which instance of Mongrel or Thin services the requests.
Passenger creates an interface between Apache or Nginx that creates an application spawning process and then forks out processes to server up incoming requests as they come in. There are a lot of configuration options for how long those processes live, how many there can be, and how many requests they will serve before they die. This is by far the most common way to scale up and handle a high traffic application, but it is not without drawbacks. This can only be done on a *nix operating system (linux, mac os x, etc). Also, these processes spin up on demand, so if no one accesses your site for a while, they processes die and the next request has the delay of it starting back up again. With Mongrel and Thin, the process is always running. Sometimes though, your processes being new and fresh can be a good thing for memory usage etc.
If it is going to be a relatively low traffic site, Mongrel or Thin provides a simple, easy to manage way to deploy the application. For higher traffic sites where you need the smart queuing and process management of something like Passenger, it is a very good solution.
As for fastcgi, you probably want to use that as a last option.
I use Passenger + nginx. It works really, really well.
To get some instant performance boast with passenger, I recommend using ruby enterprise edition.

Resources