resolve ip

pytorrent/services/reverse_dns.py

@@ -0,0 +1,99 @@
+from __future__ import annotations
+
+import ipaddress
+import socket
+import time
+from concurrent.futures import ThreadPoolExecutor, wait
+from threading import Lock
+from typing import Any
+
+_CACHE_TTL_SECONDS = 24 * 60 * 60
+_NEGATIVE_TTL_SECONDS = 60 * 60
+_CACHE_LIMIT = 2048
+_LOOKUP_LIMIT_PER_REQUEST = 24
+_LOOKUP_TIMEOUT_SECONDS = 0.8
+
+_cache: dict[str, tuple[str, float]] = {}
+_pending: dict[str, Any] = {}
+_lock = Lock()
+_executor = ThreadPoolExecutor(max_workers=3, thread_name_prefix="reverse-dns")
+
+
+def _is_resolvable_ip(value: str) -> bool:
+    try:
+        ipaddress.ip_address(str(value or "").strip())
+        return True
+    except ValueError:
+        return False
+
+
+def _lookup_host(ip: str) -> str:
+    try:
+        host = socket.gethostbyaddr(ip)[0]
+        return str(host or "").rstrip(".")
+    except Exception:
+        return ""
+
+
+def _trim_cache(now: float) -> None:
+    expired = [ip for ip, (_, expires_at) in _cache.items() if expires_at <= now]
+    for ip in expired:
+        _cache.pop(ip, None)
+    if len(_cache) <= _CACHE_LIMIT:
+        return
+    for ip, _ in sorted(_cache.items(), key=lambda item: item[1][1])[: len(_cache) - _CACHE_LIMIT]:
+        _cache.pop(ip, None)
+
+
+def _store(ip: str, host: str, now: float | None = None) -> None:
+    now = now or time.monotonic()
+    ttl = _CACHE_TTL_SECONDS if host else _NEGATIVE_TTL_SECONDS
+    _cache[ip] = (host, now + ttl)
+
+
+def attach_reverse_dns(peers: list[dict[str, Any]]) -> list[dict[str, Any]]:
+    """Attach cached or newly resolved PTR hostnames to peer rows with a small request budget."""
+    now = time.monotonic()
+    missing: list[str] = []
+    with _lock:
+        _trim_cache(now)
+        for peer in peers:
+            ip = str(peer.get("ip") or "").strip()
+            if not ip or not _is_resolvable_ip(ip):
+                peer["host"] = ""
+                continue
+            cached = _cache.get(ip)
+            if cached and cached[1] > now:
+                peer["host"] = cached[0]
+                continue
+            peer["host"] = ""
+            if ip not in _pending and ip not in missing and len(missing) < _LOOKUP_LIMIT_PER_REQUEST:
+                missing.append(ip)
+        for ip in missing:
+            _pending[ip] = _executor.submit(_lookup_host, ip)
+        futures = list(_pending.items())
+
+    if futures:
+        wait([future for _, future in futures], timeout=_LOOKUP_TIMEOUT_SECONDS)
+
+    done_hosts: dict[str, str] = {}
+    with _lock:
+        now = time.monotonic()
+        for ip, future in list(_pending.items()):
+            if not future.done():
+                continue
+            try:
+                host = str(future.result() or "")
+            except Exception:
+                host = ""
+            _store(ip, host, now)
+            done_hosts[ip] = host
+            _pending.pop(ip, None)
+
+    for peer in peers:
+        ip = str(peer.get("ip") or "").strip()
+        if ip in done_hosts:
+            peer["host"] = done_hosts[ip]
+        elif not peer.get("host") and ip in _pending:
+            peer["host_pending"] = True
+    return peers