Fix parsing of zone from path in executor API

The get() method of the executor API receives the full path to a build
request. In case of a zoned request the zone wasn't correctly derived
from the given path so that the resulting "zone" still contained the
request's UUID.

This lead to the creation of an `ExecutorQueue` for each build request
through the default factory of the `DefaultKeyDict`.

Change-Id: I9aafcee0ea24b45d095e35e242c24639dc149536

tests/unit/test_zk.py

@@ -591,6 +591,9 @@ class TestExecutorApi(ZooKeeperBaseTestCase):
         d = executor_api.get(path_d)
         e = executor_api.get(path_e)
 
+        # Make sure the get() method used the correct zone keys
+        self.assertEqual(set(executor_api.zone_queues.keys()), {"zone", None})
+
         b.state = BuildRequest.RUNNING
         executor_api.update(b)
 

zuul/zk/executor.py

@@ -131,7 +131,9 @@ class ExecutorApi:
 
     def get(self, path):
         if path.startswith(self.zones_root):
-            zone = path[len(self.zones_root):]
+            # Remove zone root so we end up with: <zone>/requests/<uuid>
+            rel_path = path[len(f"{self.zones_root}/"):]
+            zone = rel_path.split("/")[0]
         else:
             zone = None
         return self.zone_queues[zone].get(path)