Using High-Density Memory Store with Java Client

Hazelcast IMDG Enterprise HD

If you have Hazelcast IMDG Enterprise HD, your Hazelcast Java client's Near Cache can benefit from the High-Density Memory Store.

Let's recall the Java client's Near Cache configuration (please see the Configuring Client Near Cache section) without High-Density Memory Store:

</hazelcast-client>
    ...
    ...
    <near-cache name="MENU">
        <max-size>2000</max-size>
        <time-to-live-seconds>0</time-to-live-seconds>
        <max-idle-seconds>0</max-idle-seconds>
        <eviction-policy>LFU</eviction-policy>
        <invalidate-on-change>true</invalidate-on-change>
        <in-memory-format>OBJECT</in-memory-format>
    </near-cache>
    ...
</hazelcast-client>

You can configure this Near Cache to use Hazelcast's High-Density Memory Store by setting the in-memory format to NATIVE. Please see the following configuration example:

</hazelcast-client>
    ...
    ...
    <near-cache>
       ...
       <time-to-live-seconds>0</time-to-live-seconds>
       <max-idle-seconds>0</max-idle-seconds>
       <invalidate-on-change>true</invalidate-on-change>
       <in-memory-format>NATIVE</in-memory-format>
       <eviction size="1000" max-size-policy="ENTRY_COUNT" eviction-policy="LFU"/>
       ...
    </near-cache>
</hazelcast-client>

Please notice that when the in-memory format is NATIVE, i.e. High-Density Memory Store is enabled, the configuration element <eviction> is used to specify the eviction behavior of your client's Near Cache. In this case, the elements <max-size> and <eviction-policy> used in the configuration of a Near Cache without High-Density Memory Store do not have any impact.

The element <eviction> has the following attributes:

size: Maximum size (entry count) of the Near Cache.
max-size-policy: Maximum size policy for eviction of the Near Cache. Available values are as follows:
- ENTRY_COUNT: Maximum entry count per member.
- USED_NATIVE_MEMORY_SIZE: Maximum used native memory size in megabytes.
- USED_NATIVE_MEMORY_PERCENTAGE: Maximum used native memory percentage.
- FREE_NATIVE_MEMORY_SIZE: Minimum free native memory size to trigger cleanup.
- FREE_NATIVE_MEMORY_PERCENTAGE: Minimum free native memory percentage to trigger cleanup.
eviction-policy: Eviction policy configuration. Its default values is NONE. Available values are as follows:
- NONE: No items will be evicted and the property max-size will be ignored. You still can combine it with time-to-live-seconds.
- LRU: Least Recently Used.d.
- LFU: Least Frequently Used.d.

Keep in mind that you should have already enabled the High-Density Memory Store usage for your client, using the <native-memory> element in the client's configuration.

Please see the High-Density Memory Store section for more information on Hazelcast's High-Density Memory Store feature.

Hazelcast Clients Java Client Using High-Density Memory Store with Java Client