This is probably the silliest question today but...
The Rails team & many others recommend using passenger instead of a mongrel cluster, but I cannot find a clear list of exact benefits / advantages of this or what the potential pitfall are. Just wondering if anyone can help explain this?
Also is passenger its own server or does it use mongrel under the hood?
Thanks!
Before Passenger, Mongrel was the way to go, but a Mongrel cluster can be a nuisance to keep properly tuned. As your application grows in complexity, the memory footprint of each Mongrel instance will expand, and this can eat into available disk cache and degrade performance, so you'll have to pay close attention to the memory allocation balance on your deployments. From time to time you'll have to tweak it to add or remove Mongrels.
The other downside is you'll need to manage these Mongrel processes using some kind of launcher like monit and these can be fussy and difficult. Mongrel does not come with its own process manager.
Another serious problem is that each Mongrel is locked to a particular application and shifting loads between one app and another is very difficult to manage.
Mongrel is also dependent on an external load-balancer that you must configure yourself.
Passenger will handle launching all the Rails engine processes and will do its best to allocate memory efficiently. If you have a number of sites with conflicting priorities, Passenger will do a good job of launching servers on demand, and pruning them off when they're not used.
Passenger is also very quick to relaunch all instances of an application by looking for the tmp/restart.txt trigger file. You don't have to kill any processes or wait for a restart.
Under the hood, Passenger uses its own launcher and dispatch system. Although functionally it is similar to Mongrel, there are a number of significant performance improvements that Phusion has introduced that make Passenger significantly more memory-efficient than Mongrel.
Passenger is a complete package that just works and is surprisingly easy to manage. Mongrel is only a very basic web server.
Related
Just wanted to get people's opinions on using Unicorn vs Thin as a rails server. Most of the articles/benchmarks I found online seem very incomplete, so it would nice to have a centralized place to discuss it.
Unicron is a multi-processes server, while thin is an event based/non-blocking server. Event-based servers are great... if your code is asynchronous/non-blocking - vanilla rails is blocking. So unless you use non-blocking rails libraries, I really don't see the advantage of using Thin. Even worse, in a non-blocking server, if your i/o loop is blocking you're going to block the entire loop and not be able to handle any more requests until the blocking call returns. Blocking libraries are going to slow thin down!
Why did Heroku choose Thin as their default server (for cedar)? They are smart guys, so I'm sure they had a reason.
Bellow is a link that suggests replacing Thin with 4 Unicorn workers - this makes perfect sense to me.
4 Unicron workers on Heroku
Thin is easy to configure - not optimal, but it just works in the Heroku environment.
Unicorn can be more efficient, but it needs to be configured: How many workers? Preload App? What do you pick?
I have released Unicorn Heroku apps with workers set to 3, 5 and 8 - just based on how big each app is - how much code, how much memory is used and how much traffic you get all go into picking this number, and you need to monitor over time to make sure you got the number right, and your app isn't running out of memory.
Preload false - this will make your app start slower, but when Unicorn restarts a worker, this is 'safer' with network connections (memcache, postgres, mongo etc)
Preload true - this is better, but you need to handle server re-connections correctly in the pre and post fork code.
Thin has none of these issues out of the box, but you only get process of execution.
Summary: It's really hard to configure Unicorn out of the box to work well (or at all) for everyone, whereas Thin can just work to get people running with fewer support requests.
Recently (only a few months ago) the folks behind Phusion Passenger add support to Heroku. Definitely this is an alternative you should try and see if fits your needs.
Is blazing fast even with 1 dyno and the drop in response time is palpable.
A simple Passenger Ruby Heroku Demo is hosted on github.
The main benefits that Passengers on Heroku claims are:
Static asset acceleration through Nginx - Don't let your Ruby app serve static assets, let Nginx do it for you and offload your app for the really important tasks. Nginx will do a much better job.
Multiple worker processes - Instead of running only one worker on a dyno, Phusion Passenger runs multiple worker on a single dyno, thus utilizing its resources to its fullest and giving you more bang for the buck. This approach is similar to Unicorn's. But unlike Unicorn, Phusion Passenger dynamically scales the number of worker processes based on current traffic, thus freeing up resources when they're not necessary.
Memory optimizations - Phusion Passenger uses less memory than Thin and Unicorn. It also supports copy-on-write virtual memory in combination with code preloading, thus making your app use even less memory when run on Ruby 2.0.
Request/response buffering - The included Nginx buffers requests and responses, thus protecting your app against slow clients (e.g. mobile devices on mobile networks) and improving performance.
Out-of-band garbage collection - Ruby's garbage collector is slow, but why bother your visitors with long response times? Fix this by running garbage collection outside of the normal request-response cycle! This concept, first introduced by Unicorn, has been improved upon: Phusion Passenger ensures that only one request at the same time is running out-of-band garbage collection, thus eliminating all the problems Unicorn's out-of-band garbage collection has.
JRuby support - Unicorn's a better choice than Thin, but it doesn't support JRuby. Phusion Passenger does.
Hope this helps.
Heroku does not use intelligent routing - it will randomly assign jobs to dynos regardless of whether the dyno is busy. Thus, if your dyno cannot handle multiple jobs at once, you will get latency (perhaps massive latency) even if you are paying for lots of other dynos that are free. " That's right — if your app needs 80 dynos with an intelligent router, it needs 4,000 with a random router. "
http://news.rapgenius.com/James-somers-herokus-ugly-secret-lyrics
Heroku says they are working on this, and their plan is to make it easier to use Unicorn. They basically said "Oops, we didn't notice that this was a problem for a few years... and now that we look, it's definitely a problem for Thin... so I guess you need to use a different program than the one we've been pushing all this time."
http://news.rapgenius.com/Jesper-joergensen-routing-performance-update-lyrics
From the official Heroku explanation (second link above):
"Rails, in fact, does not yet reliably support concurrent request handling. This leaves Rails developers unable to leverage the additional concurrency capabilities offered by the Cedar stack, unless they move to a concurrent web server like Puma or Unicorn.
Rails apps deployed to Cedar with Thin can rather quickly end up with request queuing problems. Because the Cedar router no longer does any queuing on behalf of the app, requests queued at the dyno must wait until the single Rails process works its way through the queue. Many customers have run into this issue and we failed to take action and provide them with a better approach to deploying Rails apps on Cedar."
Also of interest is that their performance tools, including New Relic, have not been reporting time spent in the dyno queue.
http://news.rapgenius.com/Lemon-money-trees-rap-genius-response-to-heroku-lyrics
Oops.
I've been using Ruby Enterprise Edition and Passenger (for Apache, since I run Apache anyway for other things) for some time, but I'm wondering if there's a new trend about what to use on servers nowadays.
For example I've heard about Thin, Unicorn... I also know that 1.9.2 is faster than REE, but I wonder about RAM consumption. I'd rather have it consume less RAM even at the expense of some speed.
Thanks for all advice.
If you want minimal memory you should try Thin.
It does not have master worker as Unicorn or Passenger, thus uses less memory.
Suppose you have a very small app that needs to run on a small VM, then you can use 1 thin worker + nginx. I ran several rails 3.2 apps using Thin+nginx+postgres on 256MB VMs without swapping.
Unicorn is faster but it needs a master worker. It's good if you want to run on Heroku, you can set it 2 or 3 workers and be within the 512MB limit.
If your app is very big and you have too many long running requests, I would check out jRuby and Thinidad/Torquebox.
I converted a few apps from MRI+Sidekiq to jruby+Trinidad+Trinidad_Scheduler. I get about 100-200 req/sec using a pool of 50 threads in a trinidad server!
What I like about jRuby is that you can combine everything on one Rails Server. You can put together on the same JavaVM the cache_store with EHcache, Scheduling, Background processing and real multithreading.
You don't need to run redis, memcached, resque or sidekiq separately.
Im not saying they are not good, I love sidekiq and resque, but you can decrease your complexity by combining everything on one process and have high concurrency.
A more advanced and Enterprise solution is Torquebox, it has support for clustering and is super scalable. But I've had problems with my app crashing on torquebox, so i'm sticking to Trinidad for now.
The disadvantages of jRuby? MEmory! A Trinidad server will use minimum 512MB, up to 2-3GB ram.
Also, for Single Thread server, a single request from a rails app running Ruby-1.9.3 is about twice as fast as the same request on jRuby.
Another option is Puma, you can get full multithreading on MRI with puma. I myself could not get it stable enough on my apps.
So, it all depends on your requirements, memory usage, full threading and concurrency.
Apart from Passenger, have a look at Unicorn, Trinidad, Puma and Torquebox. Those seems to be the top rails servers right now.
There is an great book with an introduction of converting your Rails app to jRuby and deploy your app using several methods such as trinidad.
http://pragprog.com/book/jkdepj/deploying-with-jruby
The Torquebox Documentation is amazingly good. It's very detailed and explains really good how to use all Torquebox features.
http://torquebox.org/documentation/
I Hope that sharing my experience has helped.
Passenger is still extremely strong, especially being REE will naturally support 1.9 in the near future. The fact that your application can crash, however it won't affect anything else on your machine is an amazing feature to have. Deploying code is extremely easy because the server will continue to accept connections, which means less frustration/stress for you.
However, in terms of comparisons:
Here is a great resource is check out various comparisons(including memory consumption) with all the new servers.
It compares Thin, Unicorn, Passenger, TorqueBox, Glassfish, and Trinidad:
http://torquebox.org/news/2011/03/14/benchmarking-torquebox-round2/
Mike Lewis' link does a good job of comparing those different ruby servers. My personal experience has been with nginx/REE/Passenger and its been good. I haven't tried the others, so I can't comment on that.
However, I can speak on RAM usage. Your biggest savings of RAM will come from using 32-bit servers. In my experience (3x 3GB app servers), 64-bit REE/passenger processes took up to 2x as much RAM as their 32-bit counterparts. We saw a significant performance increase moving from 64 to 32 bit servers, everything else staying the same. Unless your application requires 64-bit, I would suggest running your application servers (not database) in 32-bit.
Passenger is still a very good choice to use so you are not behind the times or anything. It is also actively supported and has a very good development team that contributes a lot to the community. We have been using Unicorn and it has been very good. Our favorite functionality is to be able to upgrade apps/ruby/nginx without dropping a connection.
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.
My rails sites run Mongrel, I am having a problem with the amount of memory being used. My ruby-bin processes are using up about 66 MB of resident memory. How can I reduce the amount of memory used by rails?
It is not very economical to have many rails servers running on a single machine if they are eating memory at this rate. My php5 fcgi processes sit at between 15-25 MB.
I'm fairly unfamiliar with RoR, would using JRuby help? Any comments helpful in reducing memory footprint and increasing performance are more than welcome.
You might look at Phusion Passenger and Ruby Enterprise Edition, which is the de facto standard setup for Rails apps these days. One of its aims is cutting memory use. It's also simpler than having a bunch of Mongrels.
If you are not tied to apache for something else, i would also try nginx with Phusion Passenger. If you're concerned about memory usage, you should see a smaller footprint from nginx than apache, and the lastest version of Passenger will download, compile and install nginx for you with minimal headaches.
You can also replace your mongrel process with Thin which is more efficient and has recently been patched in its Garbage Collection (thru eventmachine), to make it even better.
We use thin cluster behind nginx frontends with fine results.
I wouldn't go so far as to say Passenger is the de facto standard, but it's gaining a lot of traction. We just switched to Nginx+Passenger, and our ruby app (i.e. Mongrels vs. Passenger) memory footprint dropped from about 450MB to 295MB. It can drop less, as Passenger will kill off procs if they idle (this is configurable), but of course if you're getting traffic and it's using all of the instances you have it configured to, then they'll use up memory accordingly.
Note, that we are not using Ruby Enterprise Edition in our config yet (mainly because it's not yet available at Engine Yard), but we still are seeing a smaller memory footprint. Memory was the initial top reason we made the switch, but there are other benefits, such as faster and easier configuration for scaling up or down, and so on.
I have a Ruby on Rails application that will be a CMS in way which means it's mostly DB intensive. I expect it to have decent amount of traffic so before designing I'm choosing what servers to use. Most important for me is performance.
I heard good things about Nginx and many developers in the Rails community recommends it my only concern about it was that its version is 0.8 which is Beta I believe so I was concerned about potential problems. What is your say?
Also, I want to decide between using Mongrel cluster or Phusion Passenger. What do you think?
I'm planning to user Ruby 1.9 as it has better performance that Ruby 1.8 and I will be using VPS to host my website.
My main things is performance even if it takes longer to setup one over the other.
Your opinion is highly appreciated.
Thanks,
Tam
I'd second for Passenger + Nginx. Very low memory and it's not too difficult to setup. What type of server are your deploying too? Specs? OS? I'd take that into consideration as well considering your available hardware. If you've got enough memory already, then it shouldn't be an issue whether its Passenger or Apache, just optimize and cache your app efficiently.
Two comments:
You can deploy any rails app to any of your mentioned servers, so no need to decide this once and for all now.
IMO mongrel clusters are no longer worth the trouble. Go for passenger on whatever server makes you happy.
Id recommend passenger nginx, the configs are nice and tidy plus the memory footprint is really low compared to passenger apache.