HazelCast IMap.values() giving OutofMemory on Tomcat - spring

Question

I'm still trying to get to know hazelcast and have to make a decision on whether to use it or not.
I wrote a simple application where in I startup the cache on (single node) server startup and load the Map at the same time with about 400 entries.The Object itself has two String fields. I have a service class that looksup the cache and tries to get all the values from the map.
However, I'm getting a OutofMemoryError on Java Heap Space while trying to get values out of the hazelcast map. Eventually we plan to move to a 5 node cluster to start with.
Following is the cache spring config:
<hz:hazelcast id="instance">
<hz:config>
<hz:group name="dev" password=""/>
<hz:properties>
<hz:property name="hazelcast.merge.first.run.delay.seconds">5</hz:property>
<hz:property name="hazelcast.merge.next.run.delay.seconds">5</hz:property>
</hz:properties>
<hz:network port="5701" port-auto-increment="false">
<hz:join>
<hz:multicast enabled="true" />
</hz:join>
</hz:network>
</hz:config>
</hz:hazelcast>
<hz:map instance-ref="instance" id="statusMap" name="statuses" />
Following is where the error occurs:
map = instance.getMap("statuses");
Set<Status> statuses = (Set<Status>) map.values();
return statuses;
Any other method of IMap works fine. I tried getting the keySet and size and both worked fine. It is only when I try to get the values that the OutofMemory error shows up.
java.lang.OutOfMemoryError: Java heap space
I've tried the above with a standalone java application and it works fine. I've also monitored with visual VM and don't see any spike in used Heap Memory when the error occurs which is all the more confusing. Available Heap is 1G and the used Heap was about 70MB when the error occurred.
However, when I take out cache implementation from the application, it works fine going to the Database and getting the data.
I've also tried playing around with the tomcat vm args to no success. It is the same OutofMemoryError when I access IMap.values() with or without SQLPredicate. Any help or direction in this matter will be greatly appreciated.
Thanks.

Answer 1

As the exception mentions you're running out of heap space since the values method tries to return all deserialized values at once. If they don't fit into memory you'll likely to get an OOME.
You can use paging to prevent this from happening: http://hazelcast.org/docs/latest/manual/html-single/hazelcast-documentation.html#paging-predicate-order-limit-

Answer 2

How big are your 400 entries?
And like Chris said, the whole data is being pulled in memory.
In the future we'll replace this by an iteration based approach where we'll only pull small chunks in memory instead of the whole thing.

Answer 3

I figured out the issue. The Status object was implementing "com.hazelcast.nio.serialization.Portable" for Serialization. I did not configure the corresponding serialization factory. After I configured the factory as follows, it worked fine:
<hz:serialization>
<hz:portable-factories>
<hz:portable-factory factory-id="1" class-name="ApplicationPortableFactory" />
</hz:portable-factories>
</hz:serialization>
Apologize for not giving the complete background initially as I myself noticed it later on. Thanks for replying though. I wasn't aware of the Paging Predicate and now I'm using it for sorting and paging results. Thanks again.