Question

I wanted to use Ehcache’s disk persistence with the ability to keep the data between restarts. My configuration looks like this:

<ehcache>

  <diskStore path="/tmp/blah"/>

  <defaultCache
      eternal="true"
      maxElementsInMemory="500"
      overflowToDisk="false"
      memoryStoreEvictionPolicy="LRU"
      statistics="true"/>

  <cache
          name="myCache"
      eternal="true"
      maxElementsInMemory="10"
      maxElementsOnDisk="10000"
      overflowToDisk="true"
      diskPersistent="true"
      memoryStoreEvictionPolicy="LRU"
      statistics="true"/>

</ehcache>

Using the above, I have noticed that not only /tmp/blah/myCache.data gets created but also /tmp/blah/ehcache_auto_created_<timestamp>/myCache.data. Persisted data goes into timestamped folder and the problem is that cached data can’t be reused across restarts. Also I see no point in general to have timestamped directory at all.

After few hours of debugging, I have found out that this comes from CacheManager.detectAndFixDiskStorePathConflict method. This method loops over ALL_CACHE_MANAGERS and checks if diskStorePath matches across. This results true (although there’s only one CacheManager in ALL_CACHE_MANAGERS in my case) and diskStorePath gets awkwardly renamed.

The log warning suggests to consider singleton CacheManager. My knowledge about cache managers isn’t deep but I have no intention of using more than one (especially with different settings). The only way I access net.sf.ehcache.CacheManager is via CacheManager.getInstance(), as suggested in the documentation.

Can anyone shed some light here? Is this a bug?

I am using Ehcache version 2.4.4.

Full stack trace:

main@1, prio=5, in group 'main', status: 'RUNNING'
  at net.sf.ehcache.CacheManager.detectAndFixDiskStorePathConflict(CacheManager.java:612)
  at net.sf.ehcache.CacheManager.configure(CacheManager.java:586)
  at net.sf.ehcache.CacheManager.init(CacheManager.java:359)
  at net.sf.ehcache.CacheManager.<init>(CacheManager.java:228)
  at net.sf.ehcache.hibernate.EhCacheRegionFactory.start(EhCacheRegionFactory.java:79)
  at org.hibernate.impl.SessionFactoryImpl.<init>(SessionFactoryImpl.java:250)
  at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1385)
  ...

Thanks in advance.

Answer 1

The problem was coming from the fact I have been using EhCacheRegionFactory in my hibernate bindings (the particular cache wasn’t related to Hibernate at all, but was defined on the same file).

I have switched to SingletonEhCacheRegionFactory and the problem went away.