discovery

consul/discovery

Discovery is a utility that allows you to discover healthy instances that are behind an Elastic Load Balancer.

Usage

Install the binary to /usr/bin or /usr/local/bin.

[#] elb-discovery --help
   --region, -r "us-east-1"    aws region to query [$AWS_REGION]
   --load-balancer-name        name of elb to query
   --count "1"                 Number of results to return. 0 returns all. Note: Any number that is *NOT* 1 returns as a json array.
   --private-ip-only           If set, application will only return private IP Addresses.
   --debug                     Verbose: Turn on logging.
   --help, -h                  show help
   --version, -v               print the version

Example response:

[#] elb-discovery --load-balancer-name consul --private-ip-only
10.0.3.119

[#] elb-discovery --load-balancer-name consul --count 0 --private-ip-only
["10.0.4.22","10.0.3.119"]

[#] elb-discovery --load-balancer-name consul
127.0.0.1

Defaults

• --region: Defaults to "us-east-1". This can be overridden by the ENV Variable $AWS_REGION or the --region flag.
• --count: Defaults to 1. If Count equals 0 then it will return an "unlimited" number of results.
• --private-ip-only: Defaults to false. If not set the utility will return public ip addresses.

Credentials

The utility attempts three methods of retrieving AWS Credentials and they are attempted in the order listed:

• EnvProvider: This method looks for the following environment variables: Access Key ID: AWS_ACCESS_KEY_ID or AWS_ACCESS_KEY - Secret Access Key: AWS_SECRET_ACCESS_KEY or AWS_SECRET_KEY
• SharedCredentialsProvider: This method looks for an ini file located at $HOME/.aws/credentials See here for more info.
• EC2RoleProvider: This method uses an instance role, please see iam-policy.json for an IAM Policy that works with the instance role.

Examples

For an example of how to use the json output see example.sh. We use something similar in a system init script.

Why not use Atlas?

Atlas states that they will not always be free so we have developed this so there is no need to depend on Atlas.