reap rootwrap daemon process when it is timeout

When the daemon process is timeout, it will kill itself. But the parent
doesn't reap it. This patch add a thread to wait the process to be done
once the daemon is started.

Closes-Bug: #1850241
Change-Id: Ic209b8ef86c2522ce7e4bd81ac57bf13f1706a81
(cherry picked from commit c9a57aab08)

oslo_rootwrap/client.py

@@ -85,6 +85,15 @@ class Client(object):
                             (stderr,))
         LOG.info("Spawned new rootwrap daemon process with pid=%d",
                  process_obj.pid)
+
+        def wait_process():
+            return_code = process_obj.wait()
+            LOG.info("Rootwrap daemon process exit with status: %d",
+                     return_code)
+
+        reap_process = threading.Thread(target=wait_process)
+        reap_process.daemon = True
+        reap_process.start()
         self._manager = ClientManager(socket_path, authkey)
         self._manager.connect()
         self._proxy = self._manager.rootwrap()

releasenotes/notes/reap-rootwrap-daemon-process-60aebb56d8015484.yaml

@@ -0,0 +1,11 @@
+---
+fixes:
+  - |
+    Reap the rootwrap daemon process after it is timeout and quit. When the
+    daemon process is timeout, it will kill itself. But the parent doesn't reap
+    it. Fixed this behaviour by adding a thread to wait the process to be done
+    once the daemon is started.
+
+    More info please refer the LP #1850241 [1].
+
+    [1] https://bugs.launchpad.net/oslo.rootwrap/+bug/1850241