Monitoring your production Rails application is a very important part of deploying and operating a web app. There are several more general solutions that work very well: Nagios, Munin, etc. As of late, however, several Rails specific options have come into common use. I’d like to discuss the three big players here:
The FiveRuns client has been out for about a year and offers a terrific suite of monitoring: Server load/memory, MySQL queries, Rails errors, etc. As of version 2.0 (which is in open beta is and will be released for customers during RailsConf) it also supports monitoring your mongrels. It works great, but can get a pretty expensive ( They don’t publish their prices, but I’m paying $30/server ). It is an good choice for most users.
I’ve been beta testing the NewRelic RPM service for the past few months. It’s a decent service, it’s very easy to install, but is very limited. It will monitor your server load/memory, slow queries, etc as will all the other monitoring tools. But beyond that it doesn’t offer much. You are limited to graphing only a 24 hour period of data, so you can’t see any kind of long term trends. They have an amazing backend system for collecting data and their site is the fastest and most responsive I’ve ever seen. Once they get their UI front-end featureset to match their amazing data collection system, they’re going to be awesome. As of today, they opened to the general public and released their pricing. It is based on the number of mongrel/thin instances no matter how many servers (at least that’s my understanding). For a small to medium app running up to 40 mongrels (which would probably be 2-4 servers), you’ll wind up paying $250 / month, as compared to $60-120 for FiveRuns. Overall, given the limited functionality and hefty price, I can’t yet recommend NewRelic. I hope to see it grow and quickly add more features to change my mind.
The third option is Scout App. It offers the same suite of monitoring features as the others, but goes a step further by offering a huge range of additional plugins that will allow you to customize its functionality and easily set up extra functionality such as restart dying mongrels. You can also write your own plugins. To add another scoop on this already monstrous sundae, Scout App is the cheapest of all. It will run you only $29.00 / month for four servers.
If I had to pick one service to recommend, it would likely be Scout. They provide just about everything you can ask for out of a monitoring app at the lowest price point. If anybody else has experience with these services, please add your own comments!