[JCS-73] concurrent cache access causes values loss

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: jcs-1.3
• Fix Version/s: jcs-2.0-beta-1
• Component/s: Indexed Disk Cache
• Assignee: Thomas Vandahl
• Reporter: Alexander Kleymenov
• Created: 15/Apr/10 04:26
• Updated: 12/Nov/12 11:52
• Resolved: 09/Nov/12 20:52

Description

The following groovy code demonstrates the problem: several threads write to the cache and try to read previously written values. Sometimes just written values can't be retrieved. In this case, subsequent tries can get the value, but not always.

cache = org.apache.jcs.JCS.getInstance("cache")
group = "group"
worker = {
    def name = Thread.currentThread().name
    10000.times { idx ->
        if (idx) {
            // get previously stored value
            def res = cache.getFromGroup(idx-1, group)
            if (!res) {
                // null value got inspite of the fact it was placed in cache!
                println "ERROR: for ${idx} in " + name
                // try to get the value again:
                def n = 5
                while (n-- > 0) {
                    res = cache.getFromGroup(idx-1, group)
                    if (res) {
                        // the value finally appeared in cache
                        println "ERROR FIXED for ${idx}: ${res} " + name
                        break
                    }
                    println "ERROR STILL PERSISTS for ${idx} in " + name
                    Thread.sleep(1000)
                }
            }
        }
        // put value in the cache
        cache.putInGroup(idx, group, [value:[a:1, b:2, c:3], aux:[1:'a', 2:'b', 3:'c', t:name]])
        if (!(idx % 10000)) {
            println name+" "+idx
        }
    }
}

Thread.start worker
Thread.start worker
Thread.start worker
Thread.start worker
Thread.start worker
Thread.start worker
Thread.start worker
Thread.start worker

Cache configuration:

jcs.default=CACHE
jcs.default.cacheattributes=org.apache.jcs.engine.CompositeCacheAttributes
jcs.default.cacheattributes.MaxObjects=-1
jcs.default.cacheattributes.MemoryCacheName=org.apache.jcs.engine.memory.lru.LRUMemoryCache
jcs.default.cacheattributes.DiskUsagePatternName=UPDATE
jcs.default.cacheattributes.UseMemoryShrinker=true
jcs.default.cacheattributes.MaxMemoryIdleTimeSeconds=10
jcs.default.cacheattributes.ShrinkerIntervalSeconds=10
jcs.default.elementattributes=org.apache.jcs.engine.ElementAttributes
jcs.default.elementattributes.IsRemote=false
jcs.default.elementattributes.IsLateral=false
jcs.default.elementattributes.IsSpool=true
jcs.default.elementattributes.IsEternal=true

jcs.auxiliary.CACHE=org.apache.jcs.auxiliary.disk.indexed.IndexedDiskCacheFactory
jcs.auxiliary.CACHE.attributes=org.apache.jcs.auxiliary.disk.indexed.IndexedDiskCacheAttributes
jcs.auxiliary.CACHE.attributes.DiskPath=./cache
jcs.auxiliary.CACHE.attributes.MaxPurgatorySize=-1
jcs.auxiliary.CACHE.attributes.MaxKeySize=-1
jcs.auxiliary.CACHE.attributes.MaxRecycleBinSize=500
jcs.auxiliary.CACHE.attributes.ShutdownSpoolTimeLimit=60
jcs.auxiliary.CACHE.attributes.OptimizeAtRemoveCount=30000
jcs.auxiliary.CACHE.attributes.OptimizeOnShutdown=true
jcs.auxiliary.CACHE.attributes.EventQueueType=SINGLE

Issue Links

• is duplicated by: JCS-74 Some data may be lost when adding/removing entries with the same key
• is duplicated by: JCS-76 Exception when using the cache from different threads (synchronization problems)