asg-instance-refresh

asg-instance-refresh is a minimal CLI tool to trigger an instance refresh on a EC2 autoscaling group.

Installation

GO111MODULE=off go get -u github.com/INFURA/asg-instance-refresh

Usage

asg-instance-refresh <asg-name>

Flags

• region - The AWS region. Default to us-east-1.
• strategy - the selected refresh strategy. Default to "rolling".
• warmup - How long the new instances need to warm up. Default to the value for the health check grace period defined for the group.
• minhealthy - The minimum percentage capacity to retain during the recycling. Default to 100%.
• wait - Wait until the refresh is complete to return.

Refresh strategies

asg-instance-refresh support the refresh strategies given by AWS. At the time of writing, only one strategy exist: rolling.

Because this rolling strategy is extremely slow, this tool support an additional strategy: infura-refresh. In short, this strategy works the following way:

• double the desired count
• wait for new healthy instances to appear
• enable scale-in protection on the new instances
• set back the desired count to normal
• wait for the old instances to get removed
• set the instance protection or not according to the ASG defined setting

License

MIT