Hazelcast - java.lang.IllegalArgumentException: key cannot be of type Data

Question

W've just upgraded our application from Hazelcast 3.8.0 to 3.10.1.

We am getting an error message "key cannot be of type Data!" when accessing data in Hazelcast.

java.lang.IllegalArgumentException: key cannot be of type Data!
at com.hazelcast.util.Preconditions.checkNotInstanceOf(Preconditions.java:300)
at com.hazelcast.internal.nearcache.impl.DefaultNearCache.checkKeyFormat(DefaultNearCache.java:226)
at com.hazelcast.internal.nearcache.impl.DefaultNearCache.get(DefaultNearCache.java:114)
at com.hazelcast.map.impl.tx.TransactionalMapProxySupport.getCachedValue(TransactionalMapProxySupport.java:183)
at com.hazelcast.map.impl.tx.TransactionalMapProxySupport.getInternal(TransactionalMapProxySupport.java:132)
at com.hazelcast.map.impl.tx.TransactionalMapProxy.get(TransactionalMapProxy.java:110)
at com.hazelcast.client.impl.protocol.task.transactionalmap.TransactionalMapGetMessageTask.innerCall(TransactionalMapGetMessageTask.java:43)
at com.hazelcast.client.impl.protocol.task.AbstractTransactionalMessageTask.call(AbstractTransactionalMessageTask.java:34)
at com.hazelcast.client.impl.protocol.task.AbstractCallableMessageTask.processMessage(AbstractCallableMessageTask.java:35)
at com.hazelcast.client.impl.protocol.task.AbstractMessageTask.initializeAndProcessMessage(AbstractMessageTask.java:130)
at com.hazelcast.client.impl.protocol.task.AbstractMessageTask.run(AbstractMessageTask.java:110)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
at com.hazelcast.util.executor.HazelcastManagedThread.executeRun(HazelcastManagedThread.java:64)
at com.hazelcast.util.executor.HazelcastManagedThread.run(HazelcastManagedThread.java:80)
at ------ submitted from ------.(Unknown Source)

I am 100% sure that the "key" We're using is a String. The code snippet looks like this:

 String key = getKey(blah, blah);

 TransactionContext context = client.newTransactionContext();
 context.beginTransaction();
 TransactionalMap<String, AppPrefs> dataMap = context.getMap(MAP_NAME);
 try {
        prefs = dataMap.get(key);
        context.commitTransaction();

     } catch (Throwable t) {
        LOGGER.error("Error getting AppPrefs.", t);
        context.rollbackTransaction();
     }

The line of code throwing the error is:

prefs = dataMap.get(key);

There is nothing between the line of code that sets the String

String key = getKey(blah, blah);

and the line that blows :(

Following the source code through, the TransactionalMapProxySupport's method "toNearCacheKeyWithStrategy" has this logic:

final Object toNearCacheKeyWithStrategy(Object key) {
    if (!nearCacheEnabled) {
        return key;
    }

    return serializeKeys ? ss.toData(key, partitionStrategy) : key;
}

The "DefaultNearCache" object then does a

private void checkKeyFormat(K key) {
    if (!serializeKeys) {
        checkNotInstanceOf(Data.class, key, "key cannot be of type Data!");
    }
}

So it looks like the property of "TransactionalMapProxySupport" called "serializeKeyes" must have been FALSE but the same-named property in "DefaultNearCache"must have been true :(

The history of "DefaultNearCache" in git shows that the code was changed a year ago with the message: "Changed serialize-keys default for Near Cache from true to false"

Is there some configuration I should be setting?

The config I have for the map is simply:

<near-cache name="AppPrefsCache">
  <!-- Cache locally for 10 mins -->
  <max-idle-seconds>600</max-idle-seconds>
</near-cache>

Ah! It appears that I can add a " serialize-keys" tag of (true|false) to this xml and set the value.

It appears that different bits of the Hazelcast codebase are assuming a different default value for "serialize-keys". Either it should be a mandatory element in the config or the default should be the same everywhere, yes?

Answer 1

The mentioned behavior is really a bug in Hazelcast. I've created a new GitHub issue for it, so we can handle it properly - hazelcast/hazelcast#13371 .

The workaround for versions affected by the bug is to set serialize-keys to true in the near-cache configuration. The false value won't help here.

Config config = new Config();
config.getMapConfig(testName)
    .setNearCacheConfig(new NearCacheConfig().setSerializeKeys(true));

Thanks for the report and great investigation, Peter.