feat(orchestrator): periodic prune of orchestrator_events

Every 100 ticks, trim per-dst_decky_uuid history down to 10000 rows
(oldest first). Keeps the events table bounded on long-running fleets
without paying the cost on every write.

decnet/orchestrator/worker.py

@@ -25,6 +25,13 @@ from decnet.web.db.repository import BaseRepository
 
 logger = get_logger("orchestrator")
 
+# Periodic-prune knobs. Trim per-decky history every _PRUNE_EVERY_TICKS
+# to keep orchestrator_events from unbounded growth on long-running
+# fleets. Cheap on the write path (zero overhead per tick); the cost
+# pays in once every ~100 ticks.
+_PRUNE_EVERY_TICKS = 100
+_PRUNE_PER_DST_CAP = 10000
+
 
 async def orchestrator_worker(
     repo: BaseRepository,
@@ -54,6 +61,7 @@ async def orchestrator_worker(
     control_task = asyncio.create_task(
         run_control_listener(bus, "orchestrator", shutdown),
     )
+    tick_n = 0
     try:
         while not shutdown.is_set():
             try:
@@ -66,6 +74,19 @@ async def orchestrator_worker(
                 await _one_tick(repo, driver, bus)
             except Exception as exc:  # noqa: BLE001
                 logger.error("orchestrator tick failed: %s", exc)
+            tick_n += 1
+            if tick_n % _PRUNE_EVERY_TICKS == 0:
+                try:
+                    deleted = await repo.prune_orchestrator_events(
+                        per_dst_cap=_PRUNE_PER_DST_CAP,
+                    )
+                    if deleted:
+                        logger.info(
+                            "orchestrator prune deleted=%d cap=%d",
+                            deleted, _PRUNE_PER_DST_CAP,
+                        )
+                except Exception as exc:  # noqa: BLE001
+                    logger.error("orchestrator prune failed: %s", exc)
     finally:
         for t in (heartbeat_task, control_task):
             t.cancel()