Allow using pymemcache's socket keepalive and retry mechanisms

Socket keepalive capabilities have been introduced [1][2][3] with pymemcache
3.5.0 [4][5]. These changes allow to pass keepalive configuration to the
pymemcache client.

Retry mechanisms have been implemented [6][7] with pymemcache 3.5.0 [5][8].
These changes allow to instantiate a ``RetryingClient`` by using
dogpile.cache.

[1] https://github.com/pinterest/pymemcache/commit/b289c87bb89b3ab477bd5d92c8951ab42c923923
[2] https://github.com/pinterest/pymemcache/commit/c782de1cac7cfaf4f6868d17682197022dad2d6b
[3] https://github.com/pinterest/pymemcache/commit/4d46f5ad8ddbd860e5219965df0714bdc15062f6
[4] https://github.com/pinterest/pymemcache/commit/07b5ecc21ce5d388d4312c943d79f813311e349f
[5] https://pypi.org/project/pymemcache/3.5.0/
[6] https://github.com/pinterest/pymemcache/commit/75fe5c81c35d2bcfc8e6a697aef948efbfebe8ba
[7] https://pymemcache.readthedocs.io/en/latest/getting_started.html#using-the-built-in-retrying-mechanism
[8] https://github.com/pinterest/pymemcache/commit/07b5ecc21ce5d388d4312c943d79f813311e349f

Closes: #205
Pull-request: https://github.com/sqlalchemy/dogpile.cache/pull/205
Pull-request-sha: 8a7ea5dfb0653b675f2ce9eb4873d8bf08841028

Change-Id: Ia2e76475943bc8ec86b5974217d1c92110be5b43

1 files changed, 27 insertions, 0 deletions

diff --git a/tests/cache/test_memcached_backend.py b/tests/cache/test_memcached_backend.py
index bac7445..407502a 100644
--- a/tests/cache/test_memcached_backend.py
+++ b/tests/cache/test_memcached_backend.py
@@ -2,11 +2,13 @@ import os
 import ssl
 from threading import Thread
 import time
+from unittest import mock
 from unittest import TestCase
 import weakref
 
 import pytest
 
+from dogpile.cache import make_region
 from dogpile.cache.backends.memcached import GenericMemcachedBackend
 from dogpile.cache.backends.memcached import MemcachedBackend
 from dogpile.cache.backends.memcached import PylibmcBackend
@@ -200,6 +202,17 @@ class PyMemcacheSerializerTest(
     backend = "dogpile.cache.pymemcache"
 
 
+class PyMemcacheRetryTest(_NonDistributedMemcachedTest):
+    backend = "dogpile.cache.pymemcache"
+    config_args = {
+        "arguments": {
+            "url": MEMCACHED_URL,
+            "enable_retry_client": True,
+            "retry_attempts": 3,
+        }
+    }
+
+
 class MemcachedTest(_NonDistributedMemcachedTest):
     backend = "dogpile.cache.memcached"
 
@@ -327,6 +340,20 @@ class MemcachedArgstest(TestCase):
         backend.set("foo", "bar")
         eq_(backend._clients.memcached.canary, [{"min_compress_len": 20}])
 
+    def test_pymemcache_enable_retry_client_not_set(self):
+        with mock.patch("warnings.warn") as warn_mock:
+            _ = make_region().configure(
+                "dogpile.cache.pymemcache",
+                arguments={"url": "foo", "retry_attempts": 2},
+            )
+            eq_(
+                warn_mock.mock_calls[0],
+                mock.call(
+                    "enable_retry_client is not set; retry options "
+                    "will be ignored"
+                ),
+            )
+
 
 class LocalThreadTest(TestCase):
     def setUp(self):