Fix #1: FileNotFoundError on multiple SnmpSession usages

CHANGELOG.md

@@ -15,6 +15,8 @@ To see unreleased changes, please see the [CHANGELOG on the main branch guide](h
 ### Fixed
 
 * Fix SnmpSession allow_bulk handling.
+* Fix [#1][#1]: Getting FileNotFoundError exception if multiple instances
+  of SnmpSession were previously used.
 
 ### Infrastructure
 
@@ -25,4 +27,6 @@ To see unreleased changes, please see the [CHANGELOG on the main branch guide](h
 
 ### Added
 
-* Initial implementation
+* Initial implementation
+
+[#1]: https://github.com/gufolabs/gufo_snmp/issues/1

src/gufo/snmp/client.py

@@ -115,10 +115,13 @@ async def get(self: "SnmpSession", oid: str) -> ValueType:
 
         async def get_response() -> ValueType:
             while True:
-                r_ev = asyncio.Event()
                 # Wait until data will be available
+                r_ev = asyncio.Event()
                 loop.add_reader(self._fd, r_ev.set)
-                await r_ev.wait()
+                try:
+                    await r_ev.wait()
+                finally:
+                    loop.remove_reader(self._fd)
                 # Read data or get BlockingIOError
                 # if no valid data available.
                 try:
@@ -130,8 +133,10 @@ async def get_response() -> ValueType:
         # Wait for socket became writable
         w_ev = asyncio.Event()
         loop.add_writer(self._fd, w_ev.set)
-        await w_ev.wait()
-        loop.remove_writer(self._fd)
+        try:
+            await w_ev.wait()
+        finally:
+            loop.remove_writer(self._fd)
         # Send request
         self._sock.send_get(oid)
         # Await response or timeout
@@ -167,10 +172,13 @@ async def get_many(
 
         async def get_response() -> Dict[str, ValueType]:
             while True:
-                r_ev = asyncio.Event()
                 # Wait until data will be available
+                r_ev = asyncio.Event()
                 loop.add_reader(self._fd, r_ev.set)
-                await r_ev.wait()
+                try:
+                    await r_ev.wait()
+                finally:
+                    loop.remove_reader(self._fd)
                 # Read data or get BlockingIOError
                 # if no valid data available.
                 try:
@@ -182,8 +190,10 @@ async def get_response() -> Dict[str, ValueType]:
         # Wait for socket became writable
         w_ev = asyncio.Event()
         loop.add_writer(self._fd, w_ev.set)
-        await w_ev.wait()
-        loop.remove_writer(self._fd)
+        try:
+            await w_ev.wait()
+        finally:
+            loop.remove_writer(self._fd)
         # Send request
         self._sock.send_get_many(list(oids))
         # Await response or timeout

src/gufo/snmp/getbulk.py

@@ -51,10 +51,13 @@ async def __anext__(self: "GetBulkIter") -> Tuple[str, ValueType]:
 
         async def get_response() -> List[Tuple[str, ValueType]]:
             while True:
-                r_ev = asyncio.Event()
                 # Wait until data will be available
+                r_ev = asyncio.Event()
                 loop.add_reader(self._fd, r_ev.set)
-                await r_ev.wait()
+                try:
+                    await r_ev.wait()
+                finally:
+                    loop.remove_reader(self._fd)
                 # Read data or get BlockingIOError
                 # if no valid data available.
                 try:
@@ -69,11 +72,12 @@ async def get_response() -> List[Tuple[str, ValueType]]:
             raise StopAsyncIteration
         # Send request
         loop = asyncio.get_running_loop()
-        # Wait for socket became writable
-        w_ev = asyncio.Event()
-        loop.add_writer(self._fd, w_ev.set)
-        await w_ev.wait()
-        loop.remove_writer(self._fd)
+        r_ev = asyncio.Event()
+        loop.add_writer(self._fd, r_ev.set)
+        try:
+            await r_ev.wait()
+        finally:
+            loop.remove_writer(self._fd)
         # Send request
         self._sock.send_getbulk(self._ctx)
         # Await response or timeout

src/gufo/snmp/getnext.py

@@ -43,10 +43,13 @@ async def __anext__(self: "GetNextIter") -> Tuple[str, ValueType]:
 
         async def get_response() -> Tuple[str, ValueType]:
             while True:
-                r_ev = asyncio.Event()
                 # Wait until data will be available
+                r_ev = asyncio.Event()
                 loop.add_reader(self._fd, r_ev.set)
-                await r_ev.wait()
+                try:
+                    await r_ev.wait()
+                finally:
+                    loop.remove_reader(self._fd)
                 # Read data or get BlockingIOError
                 # if no valid data available.
                 try:
@@ -58,8 +61,10 @@ async def get_response() -> Tuple[str, ValueType]:
         # Wait for socket became writable
         w_ev = asyncio.Event()
         loop.add_writer(self._fd, w_ev.set)
-        await w_ev.wait()
-        loop.remove_writer(self._fd)
+        try:
+            await w_ev.wait()
+        finally:
+            loop.remove_writer(self._fd)
         # Send request
         self._sock.send_getnext(self._ctx)
         # Await response or timeout

tests/test_snmp.py

@@ -341,3 +341,21 @@ async def inner() -> None:
             assert n > 0
 
     asyncio.run(inner())
+
+
+@pytest.mark.parametrize("allow_bulk", [False, True])
+def test_fetch_file_not_found(allow_bulk: bool, snmpd: Snmpd) -> None:
+    """Test issue #1 condition."""
+
+    async def inner() -> None:
+        for _ in range(10):
+            async with SnmpSession(
+                addr=SNMPD_ADDRESS,
+                port=SNMPD_PORT,
+                community=SNMP_COMMUNITY,
+                allow_bulk=allow_bulk,
+            ) as session:
+                async for _ in session.fetch("1.3.6.1.2.1.1.3"):
+                    pass
+
+    asyncio.run(inner())