This gem can be used to create a Parameter Group with sane defaults for your PostgreSQL RDS instances. It can also be used in a ruby program to give programmatic access to those defaults.

Note it doesn't actually create any RDS instances so no charges should be incurred via the use of this gem.


  • Ruby 2.0.0 and up
  • AWS Credentials


Configure your AWS-SDK environment. (optional)

export AWS_REGION='REGION' # ex: us-west-2
gem install rdstune

If you're using rbenv you'll want to use

rbenv rehash

To add the shim for the binary.

Commandline Usage

rdstune -h

This gem creates a Parameter Group with sane defaults for your PostgreSQL RDS instances

  -t, --type=<s>                 Type of Database Server (Web/DW/Mixed/Desktop) (default: web)
  -i, --instance-type=<s>        Generate values based on an AWS instance type
  -m, --memory=<f>               Amount of Memory on the Server (GiB)
  -c, --connections=<i>          Specify the Target Max Connections
  -o, --oversubscribe=<i>        Oversubscribe the number of connections
  -n, --name=<s>                 Name of your RDS Parameter Group
  -f, --family=<s>               Database Family (Postgres version) (default: postgres9.4)
  -a, --access-key-id=<s>        Set the AWS Access Key for the account (default: $AWS_ACCESS_KEY_ID)
  -s, --secret-access-key=<s>    Set the AWS Secret Key for the account (default: $AWS_SECRET_ACCESS_KEY)
  -r, --region=<s>               Specify the AWS Region for the account (default: $AWS_REGION) 
  -d, --dry                      Dry Run - Do not Create
  -v, --version                  Show the current version of rdstune
  -h, --help                     Show this message
  • "name" is optional. If you do not specify a name one will be generated for you in the format rdstune-$type-$memory-$connections
  • "family" is optional. Valid options are postgres9.3 and postgres9.4


While not encouraged it's often the reality that you want to tune your database for a sane number of connections but allow more. This is especially true when working with persistent connection pools across multiple applications, where most of the time you can expect any single connection to be active, but you don't expect all connections to be used at the same time.

To accommodate this i've created the oversubscribe flag on rdstune. What this will do is tune your database for --connections connections but it will set max_connections to --oversubscribe

Embedded Usage

require 'rdstune'

tune = RdsTune.new (type: 'web', memory: 2, options: { connections => 200 })

myconfig = tune.get_config

puts myconfig # => {:max_connections=>200, :maintenance_work_mem=>134217728.0, :work_mem=>10485760.0, :checkpoint_completion_target=>0.7, :shared_buffers=>536870912.0, :effective_cache_size=>2147483648.0, :checkpoint_segments=>8}


  • Allow modification of the values and have that affect other areas of the config.
  • Tests