Train Series Release Notes¶
Added a new memcached driver that uses pymemcache through dogpile.cache.
If willing to use this driver, make sure you have both dogpile.cache>=1.1.2 and pymemcache>=3.4.0 installed.
The default value for
memcache_socket_timeouthas been lowered from 3 seconds to 1 second. The positive side-effect of this can be found in downstream changes. If you deployment relies explicitly on a timeout of 3 seconds, please set that override in your configuration.
[bug 1819957] If a memcache server disappears and then reconnects when multiple memcache servers are used (specific to the python-memcached based backends) it is possible that the server will contain stale data. The default is now to supply the
flush_on_reconnectoptional argument to the backend. This means that when the service connects to a memcache server, it will flush all cached data in the server. This change only impacts the pooled backend as it is the most likely (with heavy use of greenlet) to be impacted by the problem and is the recommended production configuration.
See the help from python-memcached:
- @param flush_on_reconnect: optional flag which prevents a
scenario that can cause stale data to be read: If there’s more than one memcached server and the connection to one is interrupted, keys that mapped to that server will get reassigned to another. If the first server comes back, those keys will map to it again. If it still has its data, get()s can read stale data that was overwritten on another server. This flag is off by default for backwards compatibility.