Merge ~cjwatson/launchpad:improve-memcached-teardown into launchpad:master

[Colin Watson]

Clean up MemcachedLayer subprocess properly

The MemcachedLayer teardown procedure left a zombie process lying around, resulting in a ResourceWarning on Python >= 3.6. Go to some more effort to clean this up.

[Cristian Gonzalez (cristiangsp)]

Looks good! Edited! Again!

review: Approve

diff --git a/lib/lp/testing/layers.py b/lib/lp/testing/layers.py
index 541ef56..ebd1f96 100644
--- a/lib/lp/testing/layers.py
+++ b/lib/lp/testing/layers.py
@@ -607,6 +607,15 @@ class MemcachedLayer(BaseLayer):
         if not BaseLayer.persist_test_services:
             # Kill our memcached, and there is no reason to be nice about it.
             kill_by_pidfile(MemcachedLayer.getPidFile())
+            # Also try killing the subprocess just in case it's different
+            # from what's recorded in the pid file, to avoid deadlocking on
+            # wait().
+            try:
+                MemcachedLayer._memcached_process.kill()
+            except OSError:
+                pass
+            # Clean up the resulting zombie.
+            MemcachedLayer._memcached_process.wait()
             MemcachedLayer._memcached_process = None
 
     @classmethod