11 Things to Consider Before Deploying Your Rails Application

from: http://vinsol.com/blog 

At VinSol, we have been developing and deploying Rails applications for more than four years. During this period, we have identified some best practices that we prefer to follow while deploying rails application to production server. 

Below is the checklist of these practices: 



1. Ensure that NS records and MX records are changed if they need to be changed 

Changing nameservers will point the domain to the hosting server, and changing MX records will redirect incoming mails to the mail server. As a very first step, we should make sure that name servers of the domain are set to be the correct one. Changing MX record is a must if our application is parsing incoming mails or we wants to use other mail services for e-mail exchange, for example Gmail. 



2. Ensure some backup mechanism in place for both data as well as user uploaded content like images/documents etc. 

Since production data is very critical, we must setup backup mechanism. It could be some type of scheduled task that takes periodic backup of all critical data, Or it could be some type of backup service provided by hosting company. When we talk about critical production data, it includes production DB, content generated by application users like images, documents, etc. 



3. Ensure database indexes 

We might have done development without having proper database indexes, but we should avoid going to production without them. Adding indexes might slow down insert queries a bit but it increases the performance of read queries. It applies when application in production has percentage of read operations much more than write operations. 



4. Enable your slow query log 

This is specific to MySQL. Enabling slow query log allows MySQL to log slow running queries to a file. And this log can be used to find queries that take a long time to execute and are therefore candidates for optimization. 



5. Ensure exception capturing is in place 

We might want to be notified when something bad happens to our application. There are several hosted services available who receive and track exceptions, for example Hoptoadapp.com, GetExceptional.com etc… Either we can choose one from these hosted services or we can use “exception notifier” plugin. 



6. Ensure adding entries for cron/scheduled jobs 

Most of the applications have some functionality/jobs that need to be run periodically, for example generating invoices, sending newsletters etc. In most cases these jobs are done by a rake task. We should make sure that we have added such jobs to cron or similar program. 



7. Monitoring important processes 

To ensure that our site is up 24×7 we need to ensure that all processes that our application needs are up. There can be many processes like MySQL, Mongrel, Apache etc.. These processes are very important as our application directly depends on them. For example if MySQL process get killed accidentally, our application would not be able to connect to MySQL and will start throwing exceptions. 

We can choose any of the available monitoring tools like God, Monit, 24×7 etc… 



8. Ensure confidential data filtering 

We would never like to leak/share confidential information of our application users. We should make sure that none of the user’s confidential data like SSN, Credit card info, password are being written to log files. We might not have paid much attention on this while developing the application. 



9. Rotate log files 

Once our site is up and running, every single request write some text in log file. And hence size of the log file keeps on increasing. Larger log files can put us in trouble if we get it beyond certain size. Its difficult to manage these log files, as larger files need more memory to open and need more time to download. In one of the rescue project we did , the log file size was 3GB. 

We would recommend having logrotate setup for the application. 



10. Setup Asset Host 

Setting up asset hosts can reduce loading time by 50% or more. We must setup asset hosts for our application. Once asset hosts are all set, our static files will be delivered via asset hosts for example asset1.hostname.com, asset2.hostname.com 



11. Clearing up stale sessions 

We should make sure we should not left any stale session on the server. If our application is using DB or file system as session store, we must add a schedule task to delete stale sessions. 

These are some of the points we have identified from our past experience and we might be missing some. Feel free to always add them as comments, and I’ll keep this post updated.