nginx-configurator/ncc/sysaction.py

import os
import signal
import subprocess
import sys
import time
from collections import deque
from pathlib import Path

import click
import sysrsync


def run_shell(cmd, window_height=0):
    out = subprocess.Popen(
        cmd, stdout=subprocess.PIPE, stderr=subprocess.STDOUT, text=True
    )
    stdout = []
    if window_height:
        h = window_height
        try:
            buf = deque()
            for line in out.stdout:
                term_size = os.get_terminal_size()
                prefixed = ("  => " + line).rstrip()[: term_size[0] - 1] + "\n"
                stdout.append(line)
                buf.append(prefixed)

                if h != 0:
                    sys.stdout.write(prefixed)
                    sys.stdout.flush()
                    h -= 1
                    continue

                buf.popleft()
                sys.stdout.write(f"\x1b[{window_height}F\x1b[0J")
                sys.stdout.write("".join(buf))
                sys.stdout.flush()
        finally:
            if h < window_height:
                sys.stdout.write(f"\x1b[{window_height-h}F\x1b[0J")
            sys.stdout.flush()

    out.wait()

    return out.returncode, "".join(stdout) if stdout else out.stdout.read()


def is_keepalived_master():
    keepalived_data = Path("/tmp/keepalived.data")
    keepalived_data.unlink(missing_ok=True)  # do not read old data

    sig = int(os.getenv("KEEPALIVED_DATA_SIGNAL", signal.SIGUSR1))
    os.kill(int(Path("/run/keepalived.pid").read_text()), sig)

    # wait for keepalived
    for _ in range(10):
        time.sleep(0.05)
        if keepalived_data.exists():
            break
    else:
        raise Exception(f"keepalived did not produce data on signal {sig}")

    # TODO: could we do better?
    return "State = MASTER" in Path("/tmp/keepalived.data").read_text()