Bash function to wait for a url to be available with a fibonacci backoff

wait_for_it.sh

#!/usr/bin/env bash

# Function to wait for a url to be available with a fibonacci backoff
#
# Usage:
#  wait_for_it <url>
#
# Examples:
#  wait_for_it "http://some-service:port/path/"
#  wait_for_it "google.com"
#  wait_for_it "$1"
function wait_for_it() {
    local url=${1}

    local backoff=(1 1 2 3 5 8 13 21)
    local attempt=0

    until curl --output /dev/null --silent --head --fail "${url}"; do
        local wait=${backoff[(attempt++)]:-34}
        echo "waiting for ${url}, retry in ${wait}s"; sleep "${wait}"
    done
}

wait_for_it "$1"