Why ehcache doesn't propagate expiration events?

Question

Why ehcache doesn't propagate expiration events ? How do you deal with it ?

Here is my situation. I have two nodes that syncronize with each other using RMI. My config is below:

<cacheManagerPeerProviderFactory class="net.sf.ehcache.distribution.RMICacheManagerPeerProviderFactory"
        properties="peerDiscovery=manual, rmiUrls=//localhost:51001/sessionCache|//localhost:51002/sessionCache"/>

<cacheManagerPeerListenerFactory class="net.sf.ehcache.distribution.RMICacheManagerPeerListenerFactory"
                                 properties="hostName=0.0.0.0, port=51002, socketTimeoutMillis=2000"/>

<diskStore path="java.io.tmpdir"/>

<cache name="sessionCache"
       maxEntriesLocalHeap="20000"
       maxEntriesLocalDisk="100000"
       eternal="false"
       diskSpoolBufferSizeMB="20"
       timeToIdleSeconds="60"
       memoryStoreEvictionPolicy="LRU"
       transactionalMode="off">

    <persistence strategy="localTempSwap"/>
    <cacheEventListenerFactory class="net.sf.ehcache.distribution.RMICacheReplicatorFactory" properties="replicateAsynchronously=true" />
    <bootstrapCacheLoaderFactory
            class="net.sf.ehcache.distribution.RMIBootstrapCacheLoaderFactory"
            properties="bootstrapAsynchronously=false"
            propertySeparator=","/>
</cache>

Now imagine following scenario:

1. Login call to server A creates session which is put to replicated cache.
2. Continuous calls to server A to get session object from cache will reset timeToIdleSeconds counter for it.
3. Continue calling server A for 65 seconds to make sure that session is going to be expired on server B which was never called after session object was put into cache in step 1.
4. Call server B. Internally it will remove session object from local cache and will call RegisteredEventListeners.internalNotifyElementExpiry which ends up calling RMISynchronousCacheReplicator.notifyElementExpired.

In step 4 I expect server B to send RmiEventType.REMOVE to server A. Instead RMISynchronousCacheReplicator.notifyElementExpired has following body

public final void notifyElementExpired(final Ehcache cache, final Element element) {
    /*do not propagate expiries. The element should expire in the remote cache at the same time, thus
      preseerving coherency.
      */
}

It looks like creator of RMICacheReplicatorFactory never accounted for timeToIdleSeconds algorithm of eviction.

Is manual call of cache.replace() right after each cache.get() only way to reset TTI (timeToIdle) in cluster ?

Is additional cacheEventListener with cache.remove() call in notifyElementExpired only way to remove expired element from cluster ?

Answer 1

Well, I ended up making hack. Let me know guys if there is more elegant solution.

I created additional cache event listener which looks like this

class MyCacheEventListener(properties: Properties) extends CacheEventListener {

  override def notifyElementExpired(cache: Ehcache, element: Element): Unit = {

    cache.getCacheEventNotificationService.notifyElementRemoved(element, false)
  }

  override def notifyElementRemoved(cache: Ehcache, element: Element): Unit = {}
  override def notifyElementEvicted(cache: Ehcache, element: Element): Unit = {}
  override def notifyRemoveAll(cache: Ehcache): Unit = {}
  override def notifyElementPut(cache: Ehcache, element: Element): Unit = {}
  override def notifyElementUpdated(cache: Ehcache, element: Element): Unit = {}
  override def dispose(): Unit = {}
}

which is responsible for sending fake RmiEventType.REMOVE to cluster. It's specified with scope local in config

<cacheEventListenerFactory class="com.zzzz.MyCacheEventListenerFactory" listenFor="local" />

For refreshing I had to do this after successful cache.get()

cache.getCacheEventNotificationService.notifyElementUpdated(element, false)

It's ugly but not sure what else I could do. Frankly I think Terracotta could easily implement it in their RMICacheReplicatorFactory.