function isSystemError(err) {
    if (!err) {
        return false;
    }
    return (err.code === "ETIMEDOUT" ||
        err.code === "ESOCKETTIMEDOUT" ||
        err.code === "ECONNREFUSED" ||
        err.code === "ECONNRESET" ||
        err.code === "ENOENT" ||
        err.code === "ENOTFOUND");
}
The headers that come back from services representing
the amount of time (minimum) to wait to retry.

"retry-after-ms", "x-ms-retry-after-ms" : milliseconds
"Retry-After" : seconds or timestamp