Update the default etcd3gw endpoint to v3

* Recent versions of etcd no longer support the /v3alpha/ endpoint
* It's probably better to skip directly to the /v3/ endpoint
  as a default.
* Note that this probably means a new minor version of tooz, while
  the behaviour can be worked around in config, this is enough to
  break existing systems on upgrade.
* Updated the test to test backwards compatibility.
* Updated the tests to use etcd 3.3.27, unfortunately we need
  a newer version of pifpaf that supports 3.4 before the default
  api can be used.
* The etcd backend tests have been removed: the deprecated backend
  uses the v2 api which is no longer provided - a future commit
  should remove the deprecated backend. The etcd3gw backend is the
  replacement.

This fix is required in pifpaf, but it's not in any release:
7496e5e1c3

Depends-On: https://review.opendev.org/c/openstack/devstack/+/891353
Change-Id: Ibb5e587f6b1348794b1bf4d6405bc4a32a653c2c

.zuul.yaml

@@ -8,8 +8,6 @@
       - release-notes-jobs-python3
     check:
       jobs:
-        - tooz-tox-py38-etcd
-        - tooz-tox-py310-etcd
         - tooz-tox-py38-etcd3gw
         - tooz-tox-py310-etcd3gw
         - tooz-tox-py38-zookeeper
@@ -28,8 +26,6 @@
         - tooz-tox-py310-consul
     gate:
       jobs:
-        - tooz-tox-py38-etcd
-        - tooz-tox-py310-etcd
         - tooz-tox-py38-etcd3gw
         - tooz-tox-py310-etcd3gw
         - tooz-tox-py38-zookeeper
@@ -55,14 +51,6 @@
     vars:
       tox_envlist: py38-consul
 
-- job:
-    name: tooz-tox-py38-etcd
-    parent: openstack-tox-py38
-    description: |
-      Run tests using ``py38-etcd`` environment.
-    vars:
-      tox_envlist: py38-etcd
-
 - job:
     name: tooz-tox-py38-etcd3gw
     parent: openstack-tox-py38
@@ -131,14 +119,6 @@
     vars:
       tox_envlist: py310-consul
 
-- job:
-    name: tooz-tox-py310-etcd
-    parent: openstack-tox-py310
-    description: |
-      Run tests using ``py310-etcd`` environment.
-    vars:
-      tox_envlist: py310-etcd
-
 - job:
     name: tooz-tox-py310-etcd3gw
     parent: openstack-tox-py310

releasenotes/notes/etcd-3.4-eee8300c942a1263.yaml

@@ -0,0 +1,7 @@
+---
+upgrade:
+  - |
+    This version of tooz defaults to the `v3` endpoint for the `etcd3gw`
+    backend. The previous behavior can be restored by appending
+    `?api_version=v3alpha` to the coordination URL. The `v3alpha` and
+    `v3beta` endpoints have been deprecated by upstream etcd.

setup-etcd-env.sh

@@ -1,7 +1,7 @@
 #!/bin/bash
 set -eux
 if [ -z "$(which etcd)" ]; then
-    ETCD_VERSION=3.1.3
+    ETCD_VERSION=3.3.27
     case `uname -s` in
         Darwin)
             OS=darwin

tooz/drivers/etcd3gw.py

@@ -181,7 +181,7 @@ class Etcd3Driver(coordination.CoordinationDriverCachedRunWatchers,
     ==================  =======
     Name                Default
     ==================  =======
-    api_version         v3alpha
+    api_version         v3
     ca_cert             None
     cert_key            None
     cert_cert           None
@@ -201,7 +201,7 @@ class Etcd3Driver(coordination.CoordinationDriverCachedRunWatchers,
     DEFAULT_PORT = 2379
 
     #: Default api version if none provided
-    DEFAULT_API_VERSION = "v3alpha"
+    DEFAULT_API_VERSION = "v3"
 
     GROUP_PREFIX = b"tooz/groups/"
 

tooz/tests/__init__.py

@@ -58,7 +58,10 @@ class TestWithCoordinator(testcase.TestCase, metaclass=SkipNotImplementedMeta):
         if os.getenv("TOOZ_TEST_ETCD3"):
             self.url = self.url.replace("etcd://", "etcd3://")
         if os.getenv("TOOZ_TEST_ETCD3GW"):
-            self.url = self.url.replace("etcd://", "etcd3+http://")
+            # TODO(jan.gutter): When pifpaf supports etcd 3.4 we should use the
+            # defaults
+            self.url = self.url.replace("etcd://", "etcd3+http://") + \
+                "?api_version=v3beta"
         self.useFixture(fixtures.NestedTempfile())
         self.group_id = get_random_uuid()
         self.member_id = get_random_uuid()

tooz/tests/drivers/test_etcd3gw.py

@@ -39,14 +39,14 @@ class TestEtcd3Gw(testcase.TestCase):
                'timeout': etcd3gw_driver.Etcd3Driver.DEFAULT_TIMEOUT},
               {'coord_url': ('etcd3+https://my_host:666?ca_cert=/my/ca_cert&'
                              'cert_key=/my/cert_key&cert_cert=/my/cert_cert&'
-                             'timeout=42&api_version=v3'),
+                             'timeout=42&api_version=v3alpha'),
                'protocol': 'https',
                'host': 'my_host',
                'port': 666,
                'ca_cert': '/my/ca_cert',
                'cert_key': '/my/cert_key',
                'cert_cert': '/my/cert_cert',
-               'api_path': '/v3/',
+               'api_path': '/v3alpha/',
                'timeout': 42})
     @ddt.unpack
     @mock.patch('etcd3gw.client')