T7910: use weakref.finalize for reliable session teardown

3 files changed, 32 insertions, 21 deletions

diff --git a/python/vyos/configsession.py b/python/vyos/configsession.py
index f0a22d930..62ce34b22 100644
--- a/python/vyos/configsession.py
+++ b/python/vyos/configsession.py
@@ -16,6 +16,7 @@
 import os
 import re
 import sys
+import weakref
 import subprocess
 from tempfile import NamedTemporaryFile
 from typing import TypeAlias
@@ -199,10 +200,15 @@ class ConfigSession(object):
 
         self.shared = shared
 
+        if not self.shared and self._vyconf_session:
+            self._finalizer = weakref.finalize(
+                self, self.finalize_vyconf, self._vyconf_session
+            )
+
     def __del__(self):
         if self.shared:
             return
-        if self._vyconf_session is None:
+        if not vyconf_backend():
             try:
                 output = (
                     subprocess.check_output(
@@ -223,12 +229,14 @@ class ConfigSession(object):
                     'Could not tear down session {0}: {1}'.format(self.__session_id, e),
                     file=sys.stderr,
                 )
-        else:
-            if self._vyconf_session.session_changed():
-                Warn('Exiting with uncommitted changes')
-                self._vyconf_session.discard()
-            self._vyconf_session.exit_config_mode()
-            self._vyconf_session.teardown()
+
+    @classmethod
+    def finalize_vyconf(cls, session: VyconfSession):
+        if session.session_changed():
+            Warn('Exiting with uncommitted changes')
+            session.discard()
+        session.exit_config_mode()
+        session.teardown()
 
     def __run_command(self, cmd_list):
         p = subprocess.Popen(
diff --git a/python/vyos/configsource.py b/python/vyos/configsource.py
index 6bf794d9e..33852a182 100644
--- a/python/vyos/configsource.py
+++ b/python/vyos/configsource.py
@@ -355,13 +355,6 @@ class ConfigSourceVyconfSession(ConfigSource):
         # cf. T7374
         self._level = []
 
-    def __del__(self):
-        try:
-            if not self._vyconf_session.in_session():
-                self._vyconf_session.teardown()
-        except AttributeError:
-            pass
-
     def get_level(self):
         return self._level
 
diff --git a/python/vyos/vyconf_session.py b/python/vyos/vyconf_session.py
index 379de4e24..bf1c344b4 100644
--- a/python/vyos/vyconf_session.py
+++ b/python/vyos/vyconf_session.py
@@ -16,6 +16,7 @@
 #
 
 import os
+import weakref
 import tempfile
 from functools import wraps
 from typing import Type
@@ -64,6 +65,12 @@ class VyconfSession:
             self.__token = token
 
         self.in_config_session = in_config_session()
+
+        if not self.in_config_session:
+            # op-mode sessions are ephemeral
+            # config-mode sessions are persistent, and managed by caller (CLI or ConfigSession)
+            self._finalizer = weakref.finalize(self, self._teardown, self.__token)
+
         if self.in_config_session:
             out = vyconf_client.send_request(
                 'enter_configuration_mode', token=self.__token
@@ -73,8 +80,12 @@ class VyconfSession:
 
         self.on_error = on_error
 
+    @classmethod
+    def _teardown(cls, token):
+        vyconf_client.send_request('teardown', token)
+
     def teardown(self):
-        vyconf_client.send_request('teardown', token=self.__token)
+        self._teardown(self.__token)
 
     def exit_config_mode(self):
         if self.session_changed():
@@ -129,6 +140,11 @@ class VyconfSession:
                 out = out + res
         return out
 
+    @config_mode
+    def discard(self) -> tuple[str, int]:
+        out = vyconf_client.send_request('discard', token=self.__token)
+        return self.output(out), out.status
+
     @raise_exception
     @config_mode
     def set(self, path: list[str]) -> tuple[str, int]:
@@ -189,12 +205,6 @@ class VyconfSession:
 
     @raise_exception
     @config_mode
-    def discard(self) -> tuple[str, int]:
-        out = vyconf_client.send_request('discard', token=self.__token)
-        return self.output(out), out.status
-
-    @raise_exception
-    @config_mode
     def load_config(
         self, file_name: str, migrate: bool = False, cached: bool = False
     ) -> tuple[str, int]: