using a MapLoader for a Hazelcast distributed map within a client

[manub]

I'm evaluating Hazelcast as a distributed data grid solution for an
application I'm working on. Hazelcast is setup on a distributed
cluster, and my application uses Spring to define an Hazelcast client
in this way:

<hz:client id="hazelcastClient" group-name="dev" group-password="dev-
pass">
<hz:member>localhost:5701</hz:member>
</hz:client>
On my Hazelcast node, in the hazelcast.xml file I've setup a map, with
all the configuration needed. Let's say this map is called myMap. I
can see this map set up properly when using the Hazelcast webapp for
monitoring (mancenter).

I have now to configure the map to get injected into my bean, on the
application side. If I do something like

<hz:map id="myMap" instance-ref="hazelcastClient" name="myMap" />
And I inject this map into my bean that containst the fetching logic,
I've got no problems.

However, I've also written a class that implements MapLoader
interface, in order to handle the missing data from the cache. My
problem is now that I don't know how to tie this Maploader to the
cache I defined. If I try something like

<hz:map id="myMap" instance-ref="hazelcastClient" name="myMap">
<hz:map-store enabled="true" implementation="myMapLoader"/>
</hz:map>
I'm getting an XML parse error, as it seems that when hz:map is used
as a top-level element (and not inside a hz:config, for example), you
cannot specify inner elements. This makes me think that you need to
define a hz:config element. But it's not very clear from the
documentation if you can define a hz:config element for a client. To
me it seems that you need to use hz:config if you want your
application to be part of the cluster. I'm not sure however if it's
logically correct that my app should be part of the cluster - it's
basically a client of the data grid.

Do you have any thoughts on how can I configure my app to achieve the
behaviour I want?

Thanks!

[Mehmet Dogan]

You can not configure a map on the client side. You should configure myMap and itsMapLoader/MapStore on Hazelcast node. MapStore/MapLoader operations are executed by Hazelcast node that owns the data, not by client.

Hazelcast Node

<hz:config>


    ...
    <hz:map name="myMap" backup-count="1" max-size="0">

        <hz:map-store enabled="true" implementation="myMapLoader" />


    </hz:map>

    ...
</hz:config>

-OR- using hazelcast.xml

<map name="myMap">


    <backup-count>1</backup-count>


    <time-to-live-seconds>0</time-to-live-seconds>


    <max-idle-seconds>0</max-idle-seconds>



    <map-store enabled="true">


        <class-name>foo.bar.MyMapLoader</class-name>


        <write-delay-seconds>0</write-delay-seconds>


    </map-store>


</map>

On client side just instantiate myMap;

<hz:map id="myMap" instance-ref="hazelcastClient" name="myMap" />

When client puts to / gets from that map, the node handles client's request will call MapLoader/MapStore.

ps: just copied the answer here that I have posted to your stackoverflow question.
http://stackoverflow.com/questions/10603254/using-a-maploader-for-a-hazelcast-distributed-map-within-a-client/

@mmdogan

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