kubectl-otk-ssh

#!/bin/bash
#
# kubectl-otk-ssh
#
# this script provides a way to SSH/SSM into hosts. this is backed
# by AWS SSM and is not a true ssh. this scripts provides the functionality
# to select random hosts by status or labels or directly choose a host.
#
# Install:
#
#   place this script anywhere in your path named `kubectl-otk-ssh`
#   and then you can run it as a subcommand of `kubectl`
#
# Examples:
#   
#   kubectl otk ssh --hostname <hostname>
#   kubectl otk ssh --random
#

set -e -o pipefail

declare hosts
declare random
declare status
declare hostname

get_host_instance_id() {
    echo $(kubectl get nodes/$1 -o=custom-columns='ID:.spec.providerID' --no-headers) | cut -f5 -d/
}

get_host_region() {
    echo $(kubectl get nodes/$1 -o jsonpath='{.metadata.labels.failure-domain\.beta\.kubernetes\.io/region}')
}

get_all_hosts() {
    $(kubectl get nodes -o=custom-columns='ID:.spec.providerID' --no-headers)
}

main() {
    while [[ "$1" =~ ^- && ! "$1" == "--" ]]; do case $1 in
        -h | --hostname )
            shift; hostname=$1
            ;;
        -r | --random )
            random=1
            ;;
        -s | --status )
            shift; status=$1
            ;;
    esac; shift; done
    if [[ "$1" == '--' ]]; then shift; fi

    # check required args are provided
    if [[ -z "$hostname" ]] && [[ -z "$random" ]]; then 
        echo '[ERR] --hostname or --random need to be set' >&2
        exit
    fi

    # ensure the session-manager-plugin is installed
    if ! [ -x "$(command -v session-manager-plugin)" ]; then
        echo '[ERR] session-manager-plugin is not installed, please run `brew install session-manager-plugin`' >&2
        exit 1
    fi

    # if a hostname is specified ignore everything else and login
    # directly to that host
    if [[ -n "$hostname" ]]; then 
        aws ssm start-session --target $(get_host_instance_id $hostname) --region $(get_host_region $hostname)
        exit 0
    fi 

    # select all hosts
    for i in $(kubectl get nodes --output name --no-headers); do
        host=$(echo $i | cut -f2 -d/)
        hosts+=($host)
    done

    # select a random host
    rando=$[$RANDOM % ${#hosts[@]}]
    rando=${hosts[rando]}
    aws ssm start-session --target $(get_host_instance_id $rando) --region $(get_host_region $rando)
}

main "$@"