When working with Memcached in a Java environment, it's often necessary to purge all data from the cache. This might be needed during application testing when you want to ensure a clean state for each test, or in production when you've updated a large number of records and need to ensure the cache is in sync.
Here's an example using the widely-used
This will delete all items from your Memcached instance. The flush operation is asynchronous in nature, so changes may not reflect immediately.
Here's another example using the
xmemcached library, which provides more detailed control over the Memcached server:
flushAll() method in
xmemcached works similar to the
flush() method in
net.spy.memcached, flushing all items from the cache.
flushAll, remember these operations are powerful and will clear all keys from your cache irrespective of namespaces or other organizational units within the cache. Be sure to use them judiciously in order to avoid causing unnecessary load on your database servers by causing a sudden surge in cache misses.
Not understanding the asynchronous nature of
flush operations can lead to issues. The operation returns immediately while the actual deletion happens in the background. Trying to read or write data immediately after a flush call may lead to unexpected results.
Q: Is it bad to use Memcached's 'flush' too often?
A: Yes, flushing your cache frequently can defeat the purpose of having a cache by causing a sudden increase in cache misses and potentially overloading your database servers.
Q: Can I undo a flush operation?
A: No, once a flush operation has been initiated, it can't be undone. The only way to repopulate the cache is through normal application usage.