Wait for tcp service

connection.py

import socket
from typing import Callable
from linuxfd import timerfd
from itertools import (
        starmap,
        repeat,
        )

def wait_for_tcp_service(
        addr: str,
        port: int,
        *,
        timeout: float=5.0,
        interval: float=0.1,
        tcp_timeout_calc: Callable[[float], float] =
            lambda t: 1 if t > 1 else t
        ):

    if interval <= 0:
        raise TypeError("interval value must be positive")

    tfd = timerfd()
    tfd.settime(interval, interval)

    err_msg = f"Can't establish connection to {addr}:{port}"

    elapsed = 0
    err: Exception
    with socket.socket() as s:
        try:
            # try to fight exploding retransmision time
            s.settimeout(tcp_timeout_calc(timeout)) 
            s.connect((addr, port))
        except socket.error as e:
            err = e
        else:
            return

    with socket.socket() as s:
        for i in starmap(tfd.read, repeat([])):
            elapsed += i * interval
            if elapsed >= timeout and err:
                raise TimeoutError(err_msg) from err
            try:
                remaining = timeout - elapsed
                s.settimeout(tcp_timeout_calc(remaining))
                s.connect((addr, port))
            except socket.error as e:
                err = e
            else:
                return