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Compare instance reservations and running instances for AWS services

Project Description


Check Reserved Instances - Compare instance reservations with running instances

Inspired by epheph/ec2-check-reserved-instances, and pull request #5 by DavidGoodwin

Amazon’s reserved instances are a great way to save money when using EC2, RDS, ElastiCache, etc. An instance reservation is specified by an availability zone, instance type, and quantity. Correlating the reservations you currently have active with your running instances is a manual, time-consuming, and error prone process.

This quick little Python script uses boto3 to inspect your reserved instances and running instances to determine if you currently have any reserved instances which are not being used. Additionally, it will give you a list of non-reserved instances which could benefit from additional reserved instance allocations. The report may also be sent via email.

Regional Benefit Reserved Instances are also supported!


Install the package using pip:

$ pip install check_reserved_instances


A sample configuration file is provided for easy use. By default, the script loads the configuration from config.ini in the current directory.

$ cp config.ini.sample config.ini

Configuring AWS Accounts/Credentials

Multiple AWS accounts/regions are supported! Specify one or many sections with name [AWS <name here>]. These are the lists of AWS credentials that will be used to query for instances. Replace <name here> with a nickname will be provided in the report.

The following configuration options are supported:

  • aws_access_key_id (Required str): The AWS IAM access key for a specific user.
  • aws_secret_access_key (Required str): The AWS IAM secret key for a specific user.
  • region (Optional str): The AWS region to query for the account. Defaults to us-east-1. If multiple regions are desired, another [AWS <name here>] section is required.
  • rds (Optional bool): Boolean for whether or not to check RDS reserved instances.
  • elasticache (Optional bool): Whether or not to check ElastiCache reserved instances.

Email Report

The report can be sent via email (SMTP). Specify a section with name [Email].

The following configuration options are supported:

  • smtp_host (Required str): The hostname of the SMTP server.
  • smtp_port (Optional int): The port the server uses for SMTP. Defaults to 25.
  • smtp_user (Optional str): If your SMTP server requires authentication, specify a username. Defaults to None (no authentication).
  • smtp_password (Optional str): If your SMTP server requires authentication, specify a password. Defaults to None (no authentication).
  • smtp_recipients (Required str): The email addresses to send the email alert to. Specify one or many email addresses delimited by comma.
  • smtp_sendas (Optional str): The email address to send the emails as. Defaults to root@localhost.
  • smtp_tls (Optional bool): Whether or not the SMTP server should use TLS to connect. Defaults to False.


The following optional parameter is supported:

  • -–config : Specify a custom path to the configuration file.

Ideally, this script should be ran in a cronjob:

# Run on the first day of every month
0 0 1 * * check-reserved-instances --config config.ini

For one-time use, execute the script:

$ check-reserved-instances --config config.ini
AWS account1 Reserved Instances Report

Below is the report on EC2 reserved instances:

UNUSED RESERVATION! (1) c4.large    All     Expires in [42] days.

UNUSED RESERVATION! (1) m1.small    us-east-1b    Expires in [201] days.

UNUSED RESERVATION! (1) m2.2xlarge  us-east-1a    Expires in [60] days.

NOT RESERVED!  (1) t1.micro    us-east-1c    i-sxcs34na

NOT RESERVED!  (2) m1.small    us-east-1d    i-dfgeqa53, i-456sdf4g

NOT RESERVED!  (3) m1.medium   us-east-1d    test_instance1, i-sdf3f4d6, test_instance2

NOT RESERVED!  (1) m2.2xlarge  us-east-1b    i-21asdf4a

(23) running on-demand EC2 instances
(18) EC2 reservations

Not sending email for this report

In this example, you can easily see that an m2.2xlarge was spun up in the wrong AZ (us-east-1b vs. us-east-1a). A c4.large regional benefit reserved instance is also unutilized. The “NOT RESERVED!” section shows that you could benefit from reserving:

  • (1) t1.micro
  • (1) m1.small (not 2, since you’ll likely want to move your us-east-1b small to us-east-1d)
  • (3) m1.medium

Additionally, instance IDs or Name tags are provided for unreserved instances, and time to expiration for unused reservations are reported.

Ignoring Reservations for Running Instances

If you wish to ignore certain running instances when performing the calculation, you may tag these instances as follows:

Key: NoReservation
Value: True

NOTE: This feature is currently only supported for EC2 instances.

Required IAM Permissions

The following example IAM policy is the minimum set of permissions needed to run the reporter:

    "Version": "2012-10-17",
    "Statement": [
            "Effect": "Allow",
            "Action": [
            "Resource": "*"


  • Overhaul format of report (one table with all accounts/services?)
  • In report, add
    • time since launch with each instance in the NOT RESERVED
    • cost-savings of each UNUSED RESERVATION instance type
  • Install templates to operating system folder (ex. /etc/check-reserved-instances) for easy editing
  • Support ‘NoReservation’ tag for ElastiCache/RDS instances
  • Add support for Redshift reserved nodes


Bug reports and pull requests are welcome. If you would like to contribute, please create a pull request against master. Include unit tests if necessary, and ensure that your code passes all linters (see tox.ini).

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