Mule Cache - Cluster In Memory - deserialization issue

Question

My Mule 3.9 application exposes a rest end point. Application is clustered and on-prem managed through Runtime Manager

Condition is: the end point which kicks off the batch process should be singleton meaning only 1 process should be running on the entire cluster. If a rest endpoint is invoked again, it should result into http status 409

For this use case, I have utilized Mule Caching - Clustered - In Memory version with below configuration

<ee:object-store-caching-strategy name="caching_strategy" doc:name="caching_strategy" keyGenerationExpression="some_key" synchronized="false" entryTTL="14400000" persistent="false" />

My flow looks like below -

<flow name="some-flow" doc:description="some-flow">
   <message-properties-transformer scope="invocation" doc:name="Intialize Message Properties" mimeType="application/java">
        <add-message-property key="messageId" value="#[message.rootId]"/>
   </message-properties-transformer>

<ee:cache doc:name="inititiation" cachingStrategy-ref="caching_strategy" >
    <logger message="process cache miss" level="INFO" doc:name="process cache miss"/>
    <set-payload doc:name="initialize cache map" value="#[{'id' : flowVars.messageId}]" />
</ee:cache>

<choice doc:name="Is process already running ?" >
    <when expression="#[payload.id == flowVars.messageId]">
        <logger message="New process started" level="INFO" />
    </when>
    <otherwise>
        <logger message="Process is already running" level="WARN" />
    </otherwise>
</choice>
</flow>

As you can see, I am putting java.util.HashMap with 1 key-value pair in cache and checking if it already exists or not

    <set-payload doc:name="initialize cache map" value="#[{'id' : flowVars.messageId}]" />

Actual functionality works great in the cluster and serves the purpose !

HOWEVER application logs are full of below **WARN** statements

org.mule.util.store.MonitoredObjectStoreWrapper - 
Running expirty on org.mule.util.store.ObjectStorePartition@4648ce75 threw java.lang.IllegalArgumentException: 
Cannot deserialize with a null classloader:
Cannot deserialize with a null classloader

I am not sure what is issue? The object which is in the cache is java.util.HashMap which is serializable and only key-value pair is of String.

I sense some class loader issue, but could not bring myself close to it.

Does anybody have any clue?

Thanks Vikas

Answer 1

Had my hands on the ground and managed to resolve the issue with below configuration -

<ee:object-store-caching-strategy name="caching_strategy" doc:name="caching_strategy" keyGenerationExpression="some_key" synchronized="false" >

    <!-- this is because my flow eturns different message than cache"
    <ee:serializable-event-copy-strategy/>

    <!-- manged store without persistance -->
    <managed-store storeName="MyTaskInMemoryStoreForClusteredCaching" 
               maxEntries="1" entryTTL="14400000" 
               expirationInterval="3660000" persistent="false"/>


</ee:object-store-caching-strategy>