Can ehCache return old cached value when cache is refreshing

Question

I am using Spring framework and Java CXF services.

There are several clients accessing a fixed list of data, which are fetched from Database. Since fetching from Database is an expensive call and DB doesn't change frequently, I thought it was good to cache value.

DB refresh -> 15 times a day at indefinite intervals

Cache refresh -> Every 15 minutes.

Cache loading by call to DB takes 15 seconds.

Now, If while Cache is refreshing by making a call to DB, it takes 15 secs. Within this 15 seconds, if clients wants to access data, I am OK to send the previous data in cache. Application is that Stale and Outdated data can be tolerated instead of waiting for 15 secs (there is a delta function which brings data after the time cache was loaded which is very inexpensive). Is there a way in ehcache to return old data in cache while the new data is being loaded while cache is refreshing at regular interval of 15 minutes?

Answer 1

A consistent copy of the cache on local disk provides many possibilities for business requirements, such as working with different datasets according to time-based needs or moving datasets around to different locations. It can range from a simple key-value persistence mechanism with fast read performance, to an operational store with in-memory speeds during operation for both reads and writes.

Ehcache has a RestartStore which provides fast restartability and options for cache persistence. The RestartStore implements an on-disk mirror of the in-memory cache. After any restart, data that was last in the cache will automatically load from disk into the RestartStore, and from there the data will be available to the cache.

Cache persistence on disk is configured by adding the sub-element to a cache configuration. The sub-element includes two attributes: strategy and synchronousWrites.

<cache>
  <persistence strategy=”localRestartable|localTempSwap|none|distributed” synchronousWrites=”false|true”/>
</cache>

For more information Ehcache

Answer 2

• If you use a "cache aside" pattern and your application code is responsible for reloading the cached data, before it expires, you will observe exactly the behaviour you desire as long as the cache holds the mapping.
• If you use a "cache through" pattern, with a cache loader, then there is no way to obtain such a behaviour as when the mapping is being reloaded it will lock the key, thus blocking other threads trying to get to it at the same time.