Passing arguments to Hazelcast MapStore - cassandra

Question

I want to write my own MapStore which will access Cassandra.
I would like to be able to pass arguments such as Cassandra's address, how can I do this assuming I can use the constructor.
I'm using Dropwizard and specifically dropwizard-cassandra library.

Answer 1

#danieln
#noctarius showed the declarative way to specify properties in hazelcast.xml.
But MapLoader doesn't have a way to inject this property to the instance.
To do that, you need to implement MapLoaderLifecycleSupport interface.
Properties will me injected to init() method
public interface MapLoaderLifecycleSupport {
/**
* Initializes this MapLoader implementation. Hazelcast will call
* this method when the map is first used on the
* HazelcastInstance. Implementation can
* initialize required resources for the implementing
* mapLoader, such as reading a config file and/or creating a
* database connection. References to maps, other than the one on which
* this {#code MapLoader} is configured, can be obtained from the
* {#code hazelcastInstance} in this method's implementation.
* <p>
* On members joining a cluster, this method is executed during finalization
* of the join operation, therefore care should be taken to adhere to the
* rules for {#link com.hazelcast.spi.PostJoinAwareService#getPostJoinOperation()}.
* If the implementation executes operations which may wait on locks or otherwise
* block (e.g. waiting for network operations), this may result in a time-out and
* obstruct the new member from joining the cluster. If blocking operations are
* required for initialization of the {#code MapLoader}, consider deferring them
* with a lazy initialization scheme.
* </p>
*
* #param hazelcastInstance HazelcastInstance of this mapLoader.
* #param properties Properties set for this mapStore. see MapStoreConfig
* #param mapName name of the map.
*/
void init(HazelcastInstance hazelcastInstance, Properties properties, String mapName);
/**
* Hazelcast will call this method before shutting down.
* This method can be overridden to clean up the resources
* held by this map loader implementation, such as closing the
* database connections, etc.
*/
void destroy();
}
We don't have Cassandra example, but we do have Mongo example here at your disposal. This example illustrates the approach of passing the properties to the loader.
Also, we would gladly accept Cassandra example to hazelcast-code-samples, if you will be kind to contribute one.
If you have any questions, let me know in comments below.
Thank you
Vik

Answer 2

Hazelcast provides the option to pass properties (configuration) from inside the hazelcast.xml to the MapStore implementation. Unfortunately, you're right, there is no example in the docs that shows how to do that, but here's the link to the XSD schema: https://github.com/hazelcast/hazelcast/blob/master/hazelcast/src/main/resources/hazelcast-config-3.7.xsd#L1731
For a documentation example, I pass the info to our docs team to add one :)