Speed up API reads with data cache and faster server check/stats.

Co-authored-by: Cursor <cursoragent@cursor.com>

app.py

@@ -2,6 +2,7 @@ import os
 import sys
 import json
 import logging
+from collections import Counter
 
 from dotenv import load_dotenv
 load_dotenv()
@@ -167,6 +168,11 @@ load_translations()
 DATA_LOCK = asyncio.Lock()
 
 
+async def load_data_async():
+    """Load panel state off the event loop (uses in-process cache)."""
+    return await asyncio.to_thread(load_data)
+
+
 async def save_data_async(data):
     """Saves panel state to PostgreSQL in a thread-safe way."""
     async with DATA_LOCK:
@@ -183,6 +189,37 @@ def get_ssh(server):
     )
 
 
+def get_current_user(request: Request, data: Optional[dict] = None):
+    user_id = request.session.get('user_id')
+    if not user_id:
+        return None
+    snapshot = data if data is not None else load_data()
+    for u in snapshot.get('users', []):
+        if u['id'] == user_id:
+            return u
+    return None
+
+
+def tpl(request, template, **kwargs):
+    data = load_data()
+    lang = request.cookies.get('lang', 'en')
+    ctx = {
+        'request': request,
+        'current_user': get_current_user(request, data),
+        'site_settings': data.get('settings', {}).get('appearance', {}),
+        'captcha_settings': data.get('settings', {}).get('captcha', {}),
+        'telegram_settings': data.get('settings', {}).get('telegram', {}),
+        'bot_running': tg_bot.is_running(),
+        'lang': lang,
+        '_': lambda text_id: _t(text_id, lang),
+        'translations_json': json.dumps(TRANSLATIONS.get(lang, TRANSLATIONS.get('en', {}))),
+        # Keep for legacy JS; prefer translations_json on new pages
+        'all_translations_json': json.dumps(TRANSLATIONS),
+    }
+    ctx.update(kwargs)
+    return templates.TemplateResponse(template, ctx)
+
+
 def get_panel_local_url(request: Optional[Request] = None):
     data = load_data()
     ssl_conf = data.get('settings', {}).get('ssl', {})
@@ -1337,36 +1374,6 @@ async def sync_users_with_remnawave(data: dict):
         return 0, f"Error: {str(e)}"
 
 
-def get_current_user(request: Request):
-    user_id = request.session.get('user_id')
-    if not user_id:
-        return None
-    data = load_data()
-    for u in data.get('users', []):
-        if u['id'] == user_id:
-            return u
-    return None
-
-
-def tpl(request, template, **kwargs):
-    data = load_data()
-    lang = request.cookies.get('lang', 'en')
-    ctx = {
-        'request': request,
-        'current_user': get_current_user(request),
-        'site_settings': data.get('settings', {}).get('appearance', {}),
-        'captcha_settings': data.get('settings', {}).get('captcha', {}),
-        'telegram_settings': data.get('settings', {}).get('telegram', {}),
-        'bot_running': tg_bot.is_running(),
-        'lang': lang,
-        '_': lambda text_id: _t(text_id, lang),
-        'translations_json': json.dumps(TRANSLATIONS.get(lang, TRANSLATIONS.get('en', {}))),
-        'all_translations_json': json.dumps(TRANSLATIONS)
-    }
-    ctx.update(kwargs)
-    return templates.TemplateResponse(template, ctx)
-
-
 # ======================== Pydantic Models ========================
 
 class LoginRequest(BaseModel):
@@ -1946,22 +1953,24 @@ async def server_detail(request: Request, server_id: int):
 
 @app.get('/users', response_class=HTMLResponse, tags=["System Templates"])
 async def users_page(request: Request):
-    user = get_current_user(request)
+    data = load_data()
+    user = get_current_user(request, data)
     if not user:
         return RedirectResponse(url='/login', status_code=302)
     if user['role'] not in ('admin', 'support'):
         return RedirectResponse(url='/my', status_code=302)
-    data = load_data()
     users_list = data.get('users', [])
     # Count connections per user
     conns = data.get('user_connections', [])
+    conn_counts = Counter(c.get('user_id') for c in conns if c.get('user_id'))
     for u in users_list:
-        u['connections_count'] = sum(1 for c in conns if c['user_id'] == u['id'])
+        u['connections_count'] = conn_counts.get(u['id'], 0)
     servers = data['servers']
     return tpl(
         request, 'users.html',
         users=users_list,
         servers=servers,
+        current_user=user,
     )
 
 
@@ -2309,54 +2318,97 @@ rm -rf /opt/amnezia
         return JSONResponse({'error': str(e)}, status_code=500)
 
 
+def _docker_container_inventory(ssh) -> dict:
+    """One SSH round-trip: map container name -> running bool."""
+    out, _, _ = ssh.run_sudo_command(
+        "docker ps -a --format '{{.Names}}|{{.Status}}' 2>/dev/null"
+    )
+    inventory = {}
+    for line in (out or '').splitlines():
+        if '|' not in line:
+            continue
+        name, status = line.split('|', 1)
+        name = name.strip()
+        if not name:
+            continue
+        inventory[name] = status.strip().lower().startswith('up')
+    return inventory
+
+
+def _docker_is_ready(ssh) -> bool:
+    ver, _, vcode = ssh.run_command("docker --version 2>/dev/null")
+    return vcode == 0 and bool((ver or '').strip())
+
+
 @app.post('/api/servers/{server_id}/stats', tags=["Servers"])
 async def api_server_stats(request: Request, server_id: int):
     if not _check_admin(request):
         return JSONResponse({'error': 'Forbidden'}, status_code=403)
     try:
-        data = load_data()
+        data = await load_data_async()
         if server_id >= len(data['servers']):
             return JSONResponse({'error': 'Server not found'}, status_code=404)
         server = data['servers'][server_id]
-        ssh = get_ssh(server)
-        ssh.connect()
-        stats = {}
-        out, _, _ = ssh.run_command(
-            "top -bn1 | grep 'Cpu(s)' | awk '{print $2}' | cut -d'%' -f1 2>/dev/null || "
-            "awk '{u=$2+$4; t=$2+$4+$5; if(NR==1){pu=u;pt=t} else printf \"%.1f\", (u-pu)/(t-pt)*100}' "
-            "<(grep 'cpu ' /proc/stat) <(sleep 0.5 && grep 'cpu ' /proc/stat) 2>/dev/null"
-        )
-        try:
-            stats['cpu'] = round(float(out.strip().split('\n')[0]), 1)
-        except (ValueError, IndexError):
-            stats['cpu'] = 0
-        out, _, _ = ssh.run_command("free -b | awk 'NR==2{printf \"%d %d\", $3, $2}'")
-        try:
-            parts = out.strip().split()
-            used, total = int(parts[0]), int(parts[1])
-            stats.update(ram_used=used, ram_total=total, ram_percent=round(used / total * 100, 1) if total > 0 else 0)
-        except (ValueError, IndexError):
-            stats.update(ram_used=0, ram_total=0, ram_percent=0)
-        out, _, _ = ssh.run_command("df -B1 / | awk 'NR==2{printf \"%d %d\", $3, $2}'")
-        try:
-            parts = out.strip().split()
-            used, total = int(parts[0]), int(parts[1])
-            stats.update(disk_used=used, disk_total=total, disk_percent=round(used / total * 100, 1) if total > 0 else 0)
-        except (ValueError, IndexError):
-            stats.update(disk_used=0, disk_total=0, disk_percent=0)
-        out, _, _ = ssh.run_command(
-            "DEV=$(ip route | awk '/default/ {print $5}' | head -1); "
-            "cat /proc/net/dev | awk -v dev=\"$DEV:\" '$1==dev{printf \"%d %d\", $2, $10}'"
-        )
-        try:
-            parts = out.strip().split()
-            stats['net_rx'], stats['net_tx'] = int(parts[0]), int(parts[1])
-        except (ValueError, IndexError):
-            stats['net_rx'] = stats['net_tx'] = 0
-        out, _, _ = ssh.run_command("uptime -p 2>/dev/null || uptime")
-        stats['uptime'] = out.strip()
-        ssh.disconnect()
-        return stats
+
+        def _fetch_stats():
+            ssh = get_ssh(server)
+            ssh.connect()
+            try:
+                script = r"""
+cpu=$(top -bn1 2>/dev/null | grep 'Cpu(s)' | awk '{print $2}' | cut -d'%' -f1)
+if [ -z "$cpu" ]; then cpu=0; fi
+ram=$(free -b 2>/dev/null | awk 'NR==2{printf "%d %d", $3, $2}')
+disk=$(df -B1 / 2>/dev/null | awk 'NR==2{printf "%d %d", $3, $2}')
+dev=$(ip route 2>/dev/null | awk '/default/ {print $5; exit}')
+net=$(awk -v d="${dev}:" '$1==d{printf "%d %d", $2, $10}' /proc/net/dev 2>/dev/null)
+up=$(uptime -p 2>/dev/null || uptime)
+printf 'CPU|%s\nRAM|%s\nDISK|%s\nNET|%s\nUP|%s\n' "${cpu:-0}" "${ram:-0 0}" "${disk:-0 0}" "${net:-0 0}" "$up"
+"""
+                out, _, _ = ssh.run_command(script)
+            finally:
+                ssh.disconnect()
+
+            stats = {
+                'cpu': 0,
+                'ram_used': 0, 'ram_total': 0, 'ram_percent': 0,
+                'disk_used': 0, 'disk_total': 0, 'disk_percent': 0,
+                'net_rx': 0, 'net_tx': 0,
+                'uptime': '',
+            }
+            for line in (out or '').splitlines():
+                if '|' not in line:
+                    continue
+                key, val = line.split('|', 1)
+                key, val = key.strip(), val.strip()
+                try:
+                    if key == 'CPU':
+                        stats['cpu'] = round(float(val.split()[0] if val else 0), 1)
+                    elif key == 'RAM':
+                        parts = val.split()
+                        used, total = int(parts[0]), int(parts[1])
+                        stats.update(
+                            ram_used=used,
+                            ram_total=total,
+                            ram_percent=round(used / total * 100, 1) if total > 0 else 0,
+                        )
+                    elif key == 'DISK':
+                        parts = val.split()
+                        used, total = int(parts[0]), int(parts[1])
+                        stats.update(
+                            disk_used=used,
+                            disk_total=total,
+                            disk_percent=round(used / total * 100, 1) if total > 0 else 0,
+                        )
+                    elif key == 'NET':
+                        parts = val.split()
+                        stats['net_rx'], stats['net_tx'] = int(parts[0]), int(parts[1])
+                    elif key == 'UP':
+                        stats['uptime'] = val
+                except (ValueError, IndexError):
+                    continue
+            return stats
+
+        return await asyncio.to_thread(_fetch_stats)
     except Exception as e:
         logger.exception("Error getting server stats")
         return JSONResponse({'error': str(e)}, status_code=500)
@@ -2367,128 +2419,130 @@ async def api_check_server(request: Request, server_id: int):
     if not _check_admin(request):
         return JSONResponse({'error': 'Forbidden'}, status_code=403)
     try:
-        data = load_data()
+        data = await load_data_async()
         if server_id >= len(data['servers']):
             return JSONResponse({'error': 'Server not found'}, status_code=404)
         server = data['servers'][server_id]
-        ssh = get_ssh(server)
-        ssh.connect()
-        # Just use awg's docker checker since it uses the same command
-        manager = get_protocol_manager(ssh, 'awg')
-        status = {'connection': 'ok', 'docker_installed': manager.check_docker_installed(), 'protocols': {}}
 
-        changed = False
-        if 'protocols' not in server:
-            server['protocols'] = {}
-
-        def merge_saved_protocol_status(proto, result=None, error=None):
-            """Merge live status with saved protocol metadata.
-
-            Multi-instance protocols are source-of-truth in data.json because
-            they cannot be discovered from BASE_PROTOCOLS alone. A transient
-            check failure must not delete awg2__2/awg2__3 from the panel.
-            """
-            db_proto = server.get('protocols', {}).get(proto, {}) or {}
-            merged = dict(result or {})
-            merged.setdefault('protocol', proto)
-            if error:
-                merged['error'] = error
-            if not merged.get('port') and db_proto.get('port'):
-                merged['port'] = db_proto['port']
-            if db_proto.get('awg_params') and not merged.get('awg_params'):
-                merged['awg_params'] = db_proto.get('awg_params')
-            merged['base_protocol'] = db_proto.get('base_protocol') or protocol_base(proto)
-            merged['instance'] = db_proto.get('instance') or protocol_instance(proto)
-            merged['display_name'] = db_proto.get('display_name') or protocol_display_name(proto)
-            merged['container_name'] = db_proto.get('container_name') or protocol_container_name(proto)
-            if protocol_base(proto) == 'adguard':
-                for key in ('web_port', 'mode', 'internal_ip', 'expose_web'):
-                    if db_proto.get(key) not in (None, ''):
-                        if key == 'web_port' and merged.get('web_exposed'):
-                            continue
-                        merged[key] = db_proto[key]
-                if 'expose_web' in db_proto and 'web_exposed' not in merged:
-                    merged['web_exposed'] = bool(db_proto.get('expose_web'))
-            if protocol_base(proto) == 'nginx':
-                for key in ('domain', 'email', 'site_url'):
-                    if db_proto.get(key) not in (None, ''):
-                        merged[key] = db_proto[key]
-            return merged
-
-        def should_preserve_saved_protocol(proto, result=None, err=None):
-            """Return True when check must not remove a saved protocol record."""
-            db_proto = server.get('protocols', {}).get(proto)
-            if not db_proto:
-                return False
-            # Additional AWG-family instances are only known by their saved
-            # dynamic keys (awg__2/awg2__2/awg_legacy__2). Keep them unless
-            # the user explicitly uninstalls them.
-            if protocol_base(proto) in MULTI_INSTANCE_PROTOCOLS and protocol_instance(proto) > 1:
-                return True
-            # Do not delete any saved protocol on command/check errors; only a
-            # clean live result with container_exists=False may prune base apps.
-            if err or (result and result.get('error')):
-                return True
-            return False
-
-        def check_proto(proto):
+        def _run_check():
+            ssh = get_ssh(server)
+            ssh.connect()
             try:
-                p_manager = get_protocol_manager(ssh, proto)
-                result = _manager_call(p_manager, 'get_server_status', proto)
-                return proto, merge_saved_protocol_status(proto, result), None
-            except Exception as e:
-                return proto, merge_saved_protocol_status(proto, {}, str(e)), str(e)
+                status = {
+                    'connection': 'ok',
+                    'docker_installed': _docker_is_ready(ssh),
+                    'protocols': {},
+                }
+                inventory = _docker_container_inventory(ssh) if status['docker_installed'] else {}
 
-        protocols_to_check = list(dict.fromkeys(BASE_PROTOCOLS + list(server.get('protocols', {}).keys())))
-        # Run checks sequentially. Several managers use the same SSH connection;
-        # checking them in parallel through one SSH object can produce false
-        # negatives and previously caused dynamic AWG instances to be removed.
-        for proto in protocols_to_check:
-            proto, result, err = check_proto(proto)
-            status['protocols'][proto] = result
-            if err:
-                continue
-            if result.get('container_exists'):
-                if proto not in server['protocols']:
-                    server['protocols'][proto] = {
-                        'installed': True,
-                        'port': result.get('port', '55424'),
-                        'awg_params': result.get('awg_params', {}),
-                        'base_protocol': protocol_base(proto),
-                        'instance': protocol_instance(proto),
-                        'display_name': protocol_display_name(proto),
-                        'container_name': protocol_container_name(proto),
-                    }
+                changed = False
+                if 'protocols' not in server:
+                    server['protocols'] = {}
+
+                def merge_saved_protocol_status(proto, result=None, error=None):
+                    db_proto = server.get('protocols', {}).get(proto, {}) or {}
+                    merged = dict(result or {})
+                    merged.setdefault('protocol', proto)
+                    if error:
+                        merged['error'] = error
+                    if not merged.get('port') and db_proto.get('port'):
+                        merged['port'] = db_proto['port']
+                    if db_proto.get('awg_params') and not merged.get('awg_params'):
+                        merged['awg_params'] = db_proto.get('awg_params')
+                    merged['base_protocol'] = db_proto.get('base_protocol') or protocol_base(proto)
+                    merged['instance'] = db_proto.get('instance') or protocol_instance(proto)
+                    merged['display_name'] = db_proto.get('display_name') or protocol_display_name(proto)
+                    merged['container_name'] = db_proto.get('container_name') or protocol_container_name(proto)
                     if protocol_base(proto) == 'adguard':
-                        server['protocols'][proto].update({
-                            'mode': result.get('mode'),
-                            'internal_ip': result.get('internal_ip'),
-                            'web_port': result.get('web_port'),
-                            'expose_web': result.get('web_exposed'),
-                        })
+                        for key in ('web_port', 'mode', 'internal_ip', 'expose_web'):
+                            if db_proto.get(key) not in (None, ''):
+                                if key == 'web_port' and merged.get('web_exposed'):
+                                    continue
+                                merged[key] = db_proto[key]
+                        if 'expose_web' in db_proto and 'web_exposed' not in merged:
+                            merged['web_exposed'] = bool(db_proto.get('expose_web'))
                     if protocol_base(proto) == 'nginx':
-                        server['protocols'][proto].update({
-                            'domain': result.get('domain'),
-                            'email': result.get('email'),
-                            'site_url': result.get('site_url'),
-                        })
-                    changed = True
-            else:
-                if proto in server['protocols']:
-                    if should_preserve_saved_protocol(proto, result, err):
-                        # Keep saved dynamic instances visible as installed but stopped/unchecked.
-                        status['protocols'][proto]['container_exists'] = True
-                        status['protocols'][proto].setdefault('container_running', False)
-                        status['protocols'][proto]['status_preserved'] = True
+                        for key in ('domain', 'email', 'site_url'):
+                            if db_proto.get(key) not in (None, ''):
+                                merged[key] = db_proto[key]
+                    return merged
+
+                def should_preserve_saved_protocol(proto, result=None, err=None):
+                    db_proto = server.get('protocols', {}).get(proto)
+                    if not db_proto:
+                        return False
+                    if protocol_base(proto) in MULTI_INSTANCE_PROTOCOLS and protocol_instance(proto) > 1:
+                        return True
+                    if err or (result and result.get('error')):
+                        return True
+                    return False
+
+                def check_proto(proto):
+                    cname = protocol_container_name(proto)
+                    # Fast path: skip deep manager probes when container is absent
+                    if cname and cname not in inventory:
+                        return proto, merge_saved_protocol_status(proto, {
+                            'container_exists': False,
+                            'container_running': False,
+                            'protocol': proto,
+                        }), None
+                    try:
+                        p_manager = get_protocol_manager(ssh, proto)
+                        result = _manager_call(p_manager, 'get_server_status', proto)
+                        return proto, merge_saved_protocol_status(proto, result), None
+                    except Exception as e:
+                        return proto, merge_saved_protocol_status(proto, {}, str(e)), str(e)
+
+                protocols_to_check = list(dict.fromkeys(
+                    BASE_PROTOCOLS + list(server.get('protocols', {}).keys())
+                ))
+                for proto in protocols_to_check:
+                    proto, result, err = check_proto(proto)
+                    status['protocols'][proto] = result
+                    if err:
+                        continue
+                    if result.get('container_exists'):
+                        if proto not in server['protocols']:
+                            server['protocols'][proto] = {
+                                'installed': True,
+                                'port': result.get('port', '55424'),
+                                'awg_params': result.get('awg_params', {}),
+                                'base_protocol': protocol_base(proto),
+                                'instance': protocol_instance(proto),
+                                'display_name': protocol_display_name(proto),
+                                'container_name': protocol_container_name(proto),
+                            }
+                            if protocol_base(proto) == 'adguard':
+                                server['protocols'][proto].update({
+                                    'mode': result.get('mode'),
+                                    'internal_ip': result.get('internal_ip'),
+                                    'web_port': result.get('web_port'),
+                                    'expose_web': result.get('web_exposed'),
+                                })
+                            if protocol_base(proto) == 'nginx':
+                                server['protocols'][proto].update({
+                                    'domain': result.get('domain'),
+                                    'email': result.get('email'),
+                                    'site_url': result.get('site_url'),
+                                })
+                            changed = True
                     else:
-                        del server['protocols'][proto]
-                        changed = True
+                        if proto in server['protocols']:
+                            if should_preserve_saved_protocol(proto, result, err):
+                                status['protocols'][proto]['container_exists'] = True
+                                status['protocols'][proto].setdefault('container_running', False)
+                                status['protocols'][proto]['status_preserved'] = True
+                            else:
+                                del server['protocols'][proto]
+                                changed = True
 
-        if changed:
-            save_data(data)
+                if changed:
+                    save_data(data)
+                return status
+            finally:
+                ssh.disconnect()
 
-        ssh.disconnect()
-        return status
+        return await asyncio.to_thread(_run_check)
     except Exception as e:
         logger.exception("Error checking server")
         return JSONResponse({'error': str(e), 'connection': 'failed'}, status_code=500)
@@ -3470,9 +3524,10 @@ async def api_toggle_connection(request: Request, server_id: int, req: ToggleCon
 async def api_list_users(request: Request, search: str = '', page: int = 1, size: int = 10):
     if not _check_admin(request):
         return JSONResponse({'error': 'Forbidden'}, status_code=403)
-    data = load_data()
+    data = await load_data_async()
     all_users = data.get('users', [])
     conns = data.get('user_connections', [])
+    conn_counts = Counter(c.get('user_id') for c in conns if c.get('user_id'))
     
     # Filter
     filtered = []
@@ -3500,7 +3555,7 @@ async def api_list_users(request: Request, search: str = '', page: int = 1, size
             'telegramId': u.get('telegramId'),
             'email': u.get('email'),
             'description': u.get('description'),
-            'connections_count': sum(1 for c in conns if c['user_id'] == u['id']),
+            'connections_count': conn_counts.get(u['id'], 0),
             'traffic_used': u.get('traffic_used', 0),
             'traffic_total': u.get('traffic_total', 0),
             'traffic_limit': u.get('traffic_limit', 0),

db/store.py

@@ -6,10 +6,12 @@ FastAPI handlers keep working without a full rewrite.
 
 from __future__ import annotations
 
+import copy
 import json
 import logging
 import os
 import shutil
+import threading
 from datetime import datetime, timezone
 from pathlib import Path
 from typing import Any, Optional
@@ -21,6 +23,11 @@ from .connection import get_pool, init_schema
 
 logger = logging.getLogger(__name__)
 
+# Process-wide snapshot cache. load_data() returns a deep copy so callers can
+# mutate safely; save_data() refreshes the cache after a successful write.
+_DATA_CACHE: Optional[dict] = None
+_DATA_CACHE_LOCK = threading.RLock()
+
 DEFAULT_SETTINGS = {
     'appearance': {
         'title': 'Amnezia',
@@ -208,7 +215,13 @@ def _row_to_invite(row) -> dict:
     }
 
 
-def load_data() -> dict:
+def invalidate_data_cache() -> None:
+    global _DATA_CACHE
+    with _DATA_CACHE_LOCK:
+        _DATA_CACHE = None
+
+
+def _fetch_data_from_db() -> dict:
     init_schema()
     pool = get_pool()
     with pool.connection() as conn:
@@ -266,8 +279,20 @@ def load_data() -> dict:
     }
 
 
+def load_data() -> dict:
+    """Return panel state. Uses an in-process cache; always returns a deep copy."""
+    global _DATA_CACHE
+    with _DATA_CACHE_LOCK:
+        if _DATA_CACHE is not None:
+            return copy.deepcopy(_DATA_CACHE)
+        data = _fetch_data_from_db()
+        _DATA_CACHE = data
+        return copy.deepcopy(data)
+
+
 def save_data(data: dict) -> None:
     """Replace panel state in a single transaction (same semantics as rewriting data.json)."""
+    global _DATA_CACHE
     init_schema()
     servers = data.get('servers') or []
     users = data.get('users') or []
@@ -419,6 +444,16 @@ def save_data(data: dict) -> None:
             )
         conn.commit()
 
+    # Keep caller dict and cache aligned with what was actually persisted
+    data['servers'] = servers
+    data['users'] = users
+    data['user_connections'] = connections
+    data['api_tokens'] = tokens
+    data['invite_links'] = invite_links
+    data['settings'] = settings
+    with _DATA_CACHE_LOCK:
+        _DATA_CACHE = copy.deepcopy(data)
+
 
 def export_data_dict() -> dict:
     """Export current DB state as the legacy data.json document."""

managers/ssh_manager.py

@@ -66,7 +66,7 @@ class SSHManager:
         if not self.client:
             raise ConnectionError("Not connected to server")
 
-        logger.info(f"Running command: {command[:100]}...")
+        logger.debug(f"Running command: {command[:100]}...")
         stdin, stdout, stderr = self.client.exec_command(command, timeout=timeout)
         
         # Crucial: set timeout on the channel to prevent hanging indefinitely