Question

I am currently using Heroku’s Memcached in a Rails 3 app and would like to move over to Elasticache because the pricing is much more favorable. Is this possible? Is the configuration relatively straightforward? Is there anything that I should be aware of as regards the performance?

Answer 1

DANGER: I do NOT recommend using this solution for production use. While this does work, @btucker pointed out that it allows any Heroku-hosted app to access your ElastiCache cluster.

Yes you can. The setup is similar to the guide Heroku has on Amazon RDS. The steps that differ go like this:

1. Follow the “Get Started with Amazon ElastiCache” guide to create a cache cluster and node
2. Install the ElastiCache Command Line Toolkit

3. Allow Heroku’s servers ingress to your ElastiCache cluster like the RDS guide explains but replace the rds- commands with elasticache- ones:

   elasticache-authorize-cache-security-group-ingress \
     --cache-security-group-name default \ 
     --ec2-security-group-name default \
     --ec2-security-group-owner-id 098166147350 \
   
     # If your AWS_CREDENTIAL_FILE environment setting is configured,
     # this option is not necessary.
     --aws-credential-file ../credential-file-path.template
   

4. Set a Heroku config value for your production app with your cluster’s hostname:

   heroku config:set MEMCACHE_SERVERS=elasticachehostname.amazonaws.com
   

After that, follow the Memcache Rails setup, and you’re set.