Discover HA cluster of HashiCorp tools (Consul, Nomad, and Vault)

hashicorp-cluster-discover.sh

#!/bin/bash

hash curl || exit 1
hash jq || exit 2

usage_msg="
Usage:
    $0 <leader|followers> <consul|nomad|vault> <host_address> [<query_string>]
Examples:
    $0 leader vault my-vault.example.com
    $0 leader consul my-consul.example.com '?dc=us-dc'
    $0 followers nomad my-nomad.example.com '?region=us'
"
role="${1?"$usage_msg"}"
service="${2?"$usage_msg"}"
host_address="${3?"$usage_msg"}"
query_string="$4"

case "$service" in
    consul|nomad)
        leader_response="$(curl --silent "https://$host_address/v1/status/leader$query_string")"
        leader_response="$(jq -r "." <<< "$leader_response")"
        ;;
    vault)
        if [[ "$role" == "followers" ]]
        then
            echo "Not supported." 1>&2 ; exit 3
        fi
        leader_response="$(curl --silent "https://$host_address/v1/sys/leader$query_string")"
        leader_response="$(jq -r ".leader_cluster_address" <<< "$leader_response")"
        leader_response="${leader_response#*//}"
        ;;
    *) echo "Error: service '$service' not in <consul|nomad|vault>" 1>&2 ; exit 4 ;;
esac

case "$role" in
    leader)
        echo "$leader_response"
        ;;
    followers)
        peers_response="$(curl --silent "https://$host_address/v1/status/peers$query_string")"
        cluster_followers="$(jq -c "[ .[] | select(. != \"$leader_response\") ]" <<< "$peers_response")"
        echo "$cluster_followers"
        ;;
    *) echo "Error: role '$role' not in <leader|followers> (leader: $leader_response)" 1>&2 ; exit 5 ;;
esac