اضافه شدن قابلیت share و نگهداری بلندمدت

backend/app/db.py

@@ -6,7 +6,7 @@ to Redis. Versioned artifact keys fence out expired worker leases.
 """
 import time
 from functools import lru_cache
-from sqlalchemy import create_engine, String, Text, Float, Integer, select, update, func, text
+from sqlalchemy import create_engine, String, Text, Float, Integer, select, update, func, text, or_
 from sqlalchemy.orm import DeclarativeBase, Mapped, mapped_column, sessionmaker
 from .config import settings
 
@@ -39,6 +39,9 @@ def engine():
 @lru_cache
 def sessions(): return sessionmaker(engine(), expire_on_commit=False)
 
+def active_jobs(now):
+    return or_(Job.expires_at == -1, Job.expires_at > now)
+
 def initialize():
     # Initial schema only. Subsequent schema changes must use explicit migrations.
     if engine().dialect.name == 'postgresql':
@@ -55,7 +58,7 @@ def claim():
     now = time.time()
     with sessions().begin() as db:
         # Expired jobs are never revived. A crashed worker can be retried once.
-        eligible = ((Job.status == 'queued') | ((Job.status == 'processing') & (Job.lease_until < now))) & (Job.expires_at > now)
+        eligible = ((Job.status == 'queued') | ((Job.status == 'processing') & (Job.lease_until < now))) & active_jobs(now)
         q = select(Job).where(eligible).order_by(Job.created_at).limit(1)
         if engine().dialect.name == 'postgresql': q = q.with_for_update(skip_locked=True)
         job = db.scalar(q)