TerraHome/nixos/kubeadm/scripts/discover-inventory-from-ssh.py

#!/usr/bin/env python3

import concurrent.futures
import ipaddress
import json
import os
import subprocess
import sys
from typing import Dict, Set


def derive_prefix(payload: dict) -> str:
    explicit = os.environ.get("KUBEADM_SUBNET_PREFIX", "").strip()
    if explicit:
        return explicit

    for key in ("control_plane_vm_ipv4", "worker_vm_ipv4"):
        values = payload.get(key, {}).get("value", {})
        for ip in values.values():
            if ip:
                parts = ip.split(".")
                if len(parts) == 4:
                    return ".".join(parts[:3])

    return "10.27.27"


def ssh_hostname(ip: str, users: list[str], key_path: str, timeout_sec: int) -> tuple[str, str] | None:
    cmd_tail = [
        "-o",
        "BatchMode=yes",
        "-o",
        "IdentitiesOnly=yes",
        "-o",
        "StrictHostKeyChecking=accept-new",
        "-o",
        f"ConnectTimeout={timeout_sec}",
        "-i",
        key_path,
    ]
    for user in users:
        cmd = ["ssh", *cmd_tail, f"{user}@{ip}", "hostnamectl --static 2>/dev/null || hostname"]
        try:
            out = subprocess.check_output(cmd, stderr=subprocess.DEVNULL, text=True, timeout=timeout_sec + 2).strip()
        except Exception:
            continue
        if out:
            return out.splitlines()[0].strip(), ip
    return None


def build_inventory(names: Set[str], found: Dict[str, str], ssh_user: str) -> str:
    cp = sorted([n for n in names if n.startswith("cp-")], key=lambda x: int(x.split("-")[1]))
    wk = sorted([n for n in names if n.startswith("wk-")], key=lambda x: int(x.split("-")[1]))

    cp_pairs = " ".join(f"{n}={found[n]}" for n in cp)
    wk_pairs = " ".join(f"{n}={found[n]}" for n in wk)
    primary = cp[0] if cp else "cp-1"

    return "\n".join(
        [
            f"SSH_USER={ssh_user}",
            f"PRIMARY_CONTROL_PLANE={primary}",
            f'CONTROL_PLANES="{cp_pairs}"',
            f'WORKERS="{wk_pairs}"',
            "",
        ]
    )


def main() -> int:
    payload = json.load(sys.stdin)

    cp_names = set(payload.get("control_plane_vm_ids", {}).get("value", {}).keys())
    wk_names = set(payload.get("worker_vm_ids", {}).get("value", {}).keys())
    target_names = cp_names | wk_names
    if not target_names:
        raise SystemExit("Could not determine target node names from Terraform outputs")

    ssh_user = os.environ.get("KUBEADM_SSH_USER", "").strip() or "micqdf"
    users = [u for u in os.environ.get("SSH_USER_CANDIDATES", f"{ssh_user} root").split() if u]
    key_path = os.environ.get("SSH_KEY_PATH", os.path.expanduser("~/.ssh/id_ed25519"))
    timeout_sec = int(os.environ.get("SSH_DISCOVERY_TIMEOUT_SEC", "6"))
    max_workers = int(os.environ.get("SSH_DISCOVERY_WORKERS", "32"))

    prefix = derive_prefix(payload)
    start = int(os.environ.get("KUBEADM_SUBNET_START", "2"))
    end = int(os.environ.get("KUBEADM_SUBNET_END", "254"))

    scan_ips = [str(ipaddress.IPv4Address(f"{prefix}.{i}")) for i in range(start, end + 1)]
    found: Dict[str, str] = {}

    seen_hostnames: Dict[str, str] = {}

    def run_pass(pass_timeout: int, pass_workers: int) -> None:
        with concurrent.futures.ThreadPoolExecutor(max_workers=pass_workers) as pool:
            futures = [pool.submit(ssh_hostname, ip, users, key_path, pass_timeout) for ip in scan_ips]
            for fut in concurrent.futures.as_completed(futures):
                result = fut.result()
                if not result:
                    continue
                host, ip = result
                if host not in seen_hostnames:
                    seen_hostnames[host] = ip
                if host in target_names and host not in found:
                    found[host] = ip
                if all(name in found for name in target_names):
                    return

    run_pass(timeout_sec, max_workers)
    if not all(name in found for name in target_names):
        # Slower second pass for busy runners/networks.
        run_pass(max(timeout_sec + 2, 8), max(8, max_workers // 2))

    missing = sorted([n for n in target_names if n not in found])
    if missing:
        discovered = ", ".join(sorted(seen_hostnames.keys())[:20])
        if discovered:
            sys.stderr.write(f"Discovered hostnames during scan: {discovered}\n")
        raise SystemExit(
            "Failed SSH-based IP discovery for nodes: " + ", ".join(missing) +
            f" (scanned {prefix}.{start}-{prefix}.{end})"
        )

    sys.stdout.write(build_inventory(target_names, found, ssh_user))
    return 0


if __name__ == "__main__":
    raise SystemExit(main())