How to initiate warming when a cache is created? - ignite

Question

I'd like to to use an Ignite cluster to warm a PARTITIONED cache from an existing database. The existing database is not partitioned and expensive to scan, so I'd like to perform a single scan when the cache is created by the cluster. Once the job completes, the result would be a cache containing all data from the existing database partitioned and evenly distributed across the cluster.
How do you implement a job that runs when a cache is created by Ignite?

Answer 1

Ignite integrates with underlying stores via CacheStore [1] implementations. Refer to [2] for details about your particular use case.
[1] https://apacheignite.readme.io/docs/persistent-store
[2] https://apacheignite.readme.io/docs/data-loading

Answer 2

You can create a Service that runs once on cluster start and then cancels itself. It can use a cache to store state, so it will not run if it's deployed in the cluster a second time.
The following abstract Service runs executeOnce once per cluster the first time it's deployed after cluster start:
abstract class ExecuteOnceService extends Service {
val ExecuteOnceCacheName = "_execute_once_service"
val config = new CacheConfiguration[String, java.lang.Boolean](ExecuteOnceCacheName)
.setCacheMode(CacheMode.PARTITIONED)
.setAtomicityMode(CacheAtomicityMode.TRANSACTIONAL)
#IgniteInstanceResource
var ignite: Ignite = _
override def execute(ctx: ServiceContext): Unit = {
val cache = ignite.getOrCreateCache(config)
val executed = cache.getAndPutIfAbsent(ctx.name(), java.lang.Boolean.TRUE)
if (executed != java.lang.Boolean.TRUE) executeOnce(ctx)
ignite.services().cancel(ctx.name())
}
def executeOnce(ctx: ServiceContext): Unit
}