Ehcache synchronization principle, ehcache Synchronization

Ehcache synchronization principle, ehcache Synchronization

A problem found during a recent study on ehcache synchronization:

Currently, server A and server B synchronize information from server A to server B and use RMI for manual synchronization.

The configuration information is as follows:

<?xml version="1.0" encoding="UTF-8"?><ehcache xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"    xsi:noNamespaceSchemaLocation="ehcache.xsd" updateCheck="false"    monitoring="autodetect" dynamicConfig="true">            <cacheManagerPeerListenerFactory        class="net.sf.ehcache.distribution.RMICacheManagerPeerListenerFactory"        properties="hostName = 127.0.0.1,                    port = 50001,                    socketTimeoutMillis=10000" />        <cacheManagerPeerProviderFactory        class="net.sf.ehcache.distribution.RMICacheManagerPeerProviderFactory"        properties="peerDiscovery=manual,                      rmiUrls=//127.0.0.1:40001/clusterCache"/>        <cache name="clusterCache" maxEntriesLocalHeap="999999999" eternal="false"        timeToIdleSeconds="1800" timeToLiveSeconds="1800" overflowToDisk="false">        <cacheEventListenerFactory             class="net.sf.ehcache.distribution.RMICacheReplicatorFactory"/>     </cache></ehcache> 

Core code for synchronization:

String key = StringUtils.leftPad(Thread.currentThread().getName() + a, 20, "a");Element element = new Element(key, value);CacheInstance.cache.put(element);

All values reference the same static variable static final byte [] bytes = new byte [1024*100];

Test found a problem: Assume that a single byte [1024*100] is synchronized with 16000 data records, the size of the synchronized data is about GB. However, during the synchronization process, the network adapter of server B is monitored, no such big data is found on the NIC.

 

After analysis, we know that:

The RMI protocol is composed of java serialization and HTTP protocol. During synchronization, all the synchronized data is serialized, and the value put into the Element is actually a reference to the static variable value, by default, 1000 elements are synchronized during ehcache synchronization. Therefore, the data of these 1000 elements passing through the NIC is only one byte [1024*100.

Ehcache synchronization source code:

    private void writeReplicationQueue() {        List<EventMessage> eventMessages = extractEventMessages(maximumBatchSize);        if (!eventMessages.isEmpty()) {            for (CachePeer cachePeer : listRemoteCachePeers(eventMessages.get(0).getEhcache())) {                try {                    cachePeer.send(eventMessages);                } catch (UnmarshalException e) {                    String message = e.getMessage();                    if (message.contains("Read time out") || message.contains("Read timed out")) {                        LOG.warn("Unable to send message to remote peer due to socket read timeout. Consider increasing" +                                " the socketTimeoutMillis setting in the cacheManagerPeerListenerFactory. " +                                "Message was: " + message);                    } else {                        LOG.debug("Unable to send message to remote peer.  Message was: " + message);                    }                } catch (Throwable t) {                    LOG.warn("Unable to send message to remote peer.  Message was: " + t.getMessage(), t);                }            }        }    }

MaximumBatchSize indicates the number of elements to be synchronized. The value can be customized in the following Configuration:

<cacheEventListenerFactory             class="net.sf.ehcache.distribution.RMICacheReplicatorFactory"            properties = "asynchronousReplicationMaximumBatchSize=1"/> 

AsynchronousReplicationMaximumBatchSize = 1 indicates that an Element is synchronized at a time. In this case, the traffic passing through the NIC is actually normal.