Implement compliance key lifecycle on main service, add message retention and rate limits

backend/services/main/key_lifecycle_task.py

@@ -0,0 +1,45 @@
+"""
+Periodic key lifecycle cleanup (compliance MEK, deleted-message keys, edit history).
+Poll interval is derived from MESSAGE_RETENTION_DAYS (no separate env var).
+"""
+
+import asyncio
+import logging
+
+from .db import SessionLocal
+from .key_lifecycle import run_key_lifecycle_cleanup
+
+logger = logging.getLogger("uvicorn.error")
+
+
+def key_lifecycle_poll_seconds() -> int | None:
+    try:
+        from services.shared.message_retention import get_message_retention
+    except ImportError:
+        from backend.services.shared.message_retention import get_message_retention  # type: ignore
+    r = get_message_retention()
+    if not r.cleanup_enabled():
+        return None
+    sec = r.retention_timedelta().total_seconds()
+    # Bound poll: responsive after cutoff without hammering the DB
+    return max(15, min(3600, max(1, int(sec / 1000))))
+
+
+async def start_key_lifecycle_cleanup_task(interval_seconds: int) -> None:
+    while True:
+        try:
+            with SessionLocal() as db:
+                run_key_lifecycle_cleanup(db)
+        except asyncio.CancelledError:
+            break
+        except Exception as e:
+            logger.error("Error in key lifecycle cleanup task: %s", e)
+            try:
+                await asyncio.sleep(60)
+            except asyncio.CancelledError:
+                break
+            continue
+        try:
+            await asyncio.sleep(interval_seconds)
+        except asyncio.CancelledError:
+            break