fix(mint): graceful shutdown of background tasks and db connections

cashu/lightning/base.py

@@ -119,6 +119,10 @@ def assert_unit_supported(self, unit: Unit):
         if unit not in self.supported_units:
             raise Unsupported(f"Unit {unit} is not supported")
 
+    async def cleanup(self) -> None:
+        """Cleanup method for backends to release resources like connections"""
+        pass
+
     @abstractmethod
     def __init__(self, unit: Unit, **kwargs):
         pass

cashu/lightning/blink.py

@@ -85,6 +85,12 @@ def __init__(self, unit: Unit = Unit.sat, **kwargs):
             timeout=None,
         )
 
+    async def cleanup(self):
+        try:
+            await self.client.aclose()
+        except RuntimeError as e:
+            logger.warning(f"Error closing wallet connection: {e}")
+
     async def status(self) -> StatusResponse:
         try:
             data = {

cashu/lightning/fake.py

@@ -63,6 +63,16 @@ class FakeWallet(LightningBackend):
     def __init__(self, unit: Unit = Unit.sat, **kwargs):
         self.assert_unit_supported(unit)
         self.unit = unit
+        self.tasks: set[asyncio.Task] = set()
+
+    async def cleanup(self) -> None:
+        """Cancel any running background tasks when the backend is cleaned up."""
+        for task in self.tasks:
+            if not task.done():
+                task.cancel()
+        if self.tasks:
+            await asyncio.gather(*self.tasks, return_exceptions=True)
+            self.tasks.clear()
 
     async def status(self) -> StatusResponse:
         return StatusResponse(
@@ -179,7 +189,9 @@ async def create_invoice(
         payment_request = encode(bolt11, self.privkey)
 
         if settings.fakewallet_brr:
-            asyncio.create_task(self.mark_invoice_paid(bolt11))
+            task = asyncio.create_task(self.mark_invoice_paid(bolt11))
+            self.tasks.add(task)
+            task.add_done_callback(self.tasks.discard)
 
         return InvoiceResponse(
             ok=True, checking_id=payment_hash, payment_request=payment_request

cashu/lightning/lnbits.py

@@ -45,6 +45,12 @@ def __init__(self, unit: Unit = Unit.sat, **kwargs):
         self.ws_url = f"{self.endpoint.replace('http', 'ws', 1)}/api/v1/ws/{settings.mint_lnbits_key}"
         self.old_api = True
 
+    async def cleanup(self):
+        try:
+            await self.client.aclose()
+        except RuntimeError as e:
+            logger.warning(f"Error closing wallet connection: {e}")
+
     async def status(self) -> StatusResponse:
         try:
             r = await self.client.get(url=f"{self.endpoint}/api/v1/wallet", timeout=15)

cashu/lightning/lndrest.py

@@ -105,6 +105,12 @@ def __init__(self, unit: Unit = Unit.sat, **kwargs):
         if self.supports_mpp:
             logger.info("LNDRestWallet enabling MPP feature")
 
+    async def cleanup(self):
+        try:
+            await self.client.aclose()
+        except RuntimeError as e:
+            logger.warning(f"Error closing wallet connection: {e}")
+
     async def status(self) -> StatusResponse:
         try:
             r = await self.client.get("/v1/balance/channels")

cashu/lightning/strike.py

@@ -2,6 +2,7 @@
 from typing import AsyncGenerator, Dict, Optional, Union
 
 import httpx
+from loguru import logger
 from pydantic import BaseModel
 
 from ..core.base import Amount, MeltQuote, Unit
@@ -133,6 +134,12 @@ def __init__(self, unit: Unit, **kwargs):
             timeout=None,
         )
 
+    async def cleanup(self):
+        try:
+            await self.client.aclose()
+        except RuntimeError as e:
+            logger.warning(f"Error closing wallet connection: {e}")
+
     async def status(self) -> StatusResponse:
         try:
             r = await self.client.get(url=f"{self.endpoint}/v1/balances", timeout=15)

cashu/mint/ledger.py

@@ -190,8 +190,6 @@ async def _check_backends(self) -> None:
         logger.info(f"Data dir: {settings.cashu_dir}")
 
     async def shutdown_ledger(self) -> None:
-        logger.debug("Disconnecting from database")
-        await self.db.engine.dispose()
         logger.debug("Shutting down invoice listeners")
         for task in self.invoice_listener_tasks:
             task.cancel()
@@ -201,6 +199,20 @@ async def shutdown_ledger(self) -> None:
         for task in self.regular_tasks:
             task.cancel()
 
+        # Wait for all background tasks to finish cancellation
+        tasks_to_wait = self.invoice_listener_tasks + self.watchdog_tasks + self.regular_tasks
+        if tasks_to_wait:
+            await asyncio.gather(*tasks_to_wait, return_exceptions=True)
+
+        logger.debug("Shutting down backends")
+        for method, unitbackends in self.backends.items():
+            for unit, backend in unitbackends.items():
+                if hasattr(backend, "cleanup"):
+                    await backend.cleanup()
+
+        logger.debug("Disconnecting from database")
+        await self.db.engine.dispose()
+
     async def _check_pending_proofs_and_melt_quotes(self):
         """Startup routine that checks all pending melt quotes and either invalidates
         their pending proofs for a successful melt or deletes them if the melt failed.