Backoff in Bash

backoff.sh

function backoff_delay {
  local -r -i factor=${BACKOFF_FACTOR-2}
  local -i min=$(($1*$factor))
  local -r -i max=$2
  if [[ $max < $min ]]; then
    min=$max
  fi
  echo $min
}

function with_backoff {
  local -r -i max_attempts=${BACKOFF_MAX_ATTEMPTS-3}
  local -i attempts=0
  local -r -i max_delay=${BACKOFF_MAX_DELAY-30}
  local -i delay=1
  local exit_code=1
  while [[ $((attempts++)) < $max_attempts ]]; do
    "$@" && return 0
    exit_code=$?
    sleep $delay
    delay=$(backoff_delay $delay $max_delay)
  done
  return $exit_code
}