gets function in memcached is used when you want to retrieve the value of a specific key and its CAS (Check And Set) token. This operation is typically used when you want to perform compare-and-swap operations, which are important for avoiding race conditions when updating values.
Here's an example using pymemcache, a python client for memcached:
In this example, we set a key in memcached using the
set method. We then use the
gets method to retrieve both the value associated with the key and its CAS token.
Please note that not all memcached clients support
gets, pymemcache being one of them that does.
The CAS token can be used to avoid race conditions during updates. However, it should be noted that not all memcached operations preserve the CAS token. In general, only the
prepend operations do.
gets returns None for both the value and the CAS token, it means that the specified key does not exist in the cache. Always ensure to check if a key exists before proceeding with operations that require the key.
Assuming that all memcached clients support
gets: Always validate the capabilities of your client library before starting to use specific commands such as
None returned by
gets returns None, it means either the key doesn't exist or an error occurred. Always handle these cases in your application code.
Q: What is the CAS token used for in memcached?
A: The CAS token in memcached is a unique identifier for each key-value pair. It's used primarily for the compare-and-swap (
cas) operation which allows you to only update a value if it hasn't been changed since you last fetched it.
Q: How can I retrieve just the value without the CAS token?
A: You can use the
get method instead of
gets to retrieve just the value associated with a key.