How to do multi-threaded writing in ehcache? - ehcache

Question

Here's my code of using ehcache when I do multi-threaded reading and writing:
write code:
try {
targetCache.acquireWriteLockOnKey(key);
targetCache.putIfAbsent(new Element(key, value));
}
finally {
targetCache.releaseWriteLockOnKey(key);
}
reading code：
try{
cache.acquireReadLockOnKey(key);
cacheCarId = (String)ele.getObjectValue();
}
finally {
cache.releaseReadLockOnKey(key);
}
key and value are both String.
My config is as follows：
CacheConfiguration config = new CacheConfiguration();
config.name("carCache");
config.maxBytesLocalHeap(128, MemoryUnit.parseUnit("M"));
config.eternal(false);
config.timeToLiveSeconds(60);
config.setTimeToIdleSeconds(60);
SizeOfPolicyConfiguration sizeOfPolicyConfiguration = new SizeOfPolicyConfiguration();
sizeOfPolicyConfiguration.maxDepth(10000);
sizeOfPolicyConfiguration.maxDepthExceededBehavior("abort");
config.addSizeOfPolicy(sizeOfPolicyConfiguration);
Cache memoryOnlyCache = new Cache(config);
CacheManager.getInstance().addCache(memoryOnlyCache);
Values are evict within 60s and will be written by multi-thread. The total number of key is less than 25,000.
The reading and writing was ok at the beginning, but after a couple of hours, i get inconsistence of reading and writing...
Could Anybody help me with this problem? Thanks a lot

Answer 1

A Cache is already a thread safe data structure, so you should not need to use explicit locking as you do.
Also the method Cache.putIfAbsent is already an atomic operation that guarantees that only one thread will succeed with the put.
Note that eviction and expiry are two different things. With your configuration, eviction happens when the cache size grows beyond 128MB and expiry indeed happens after 60 seconds. However Ehcache does expiry in-line, so it is triggered when you read or write the mapping.
As for your remark on inconsistence, you will need to describe in more detail what you mean by that.