Hazelcast IMap TTL Expiry - hazelcast

Question

How to invoke a method to sync the data to some DB or Kafka once the TTL set is expired during the put method of IMap class.
eg:IMap.put(key,value,TTL,TimeUnit.SECONDS);
if the above TTL is set to like 10 seconds i must call some store or some mechanism where i could sync that key and value to DB or Kafka in real time. As of now when i tried the store method it is immediately calling the method instead of 10 seconds wait time.

Answer 1

You may set an EntryExpiredListener to your map config.
It feeds on two sources of expiration based eviction, they are max-idle-seconds and time-to-live-seconds.
Example Listener class:
#Slf4j
public class MyExpiredEntryListener implements EntryExpiredListener<String, String>, MapListener {
#Override
public void entryExpired(EntryEvent<String, String> event) {
log.info("entry Expired {}", event);
}
}
You can add this config via programmatically or you may set mapconfig via xml config file.
Example usage:
public static void main(String[] args) {
Config config = new Config();
MapConfig mapConfig = config.getMapConfig("myMap");
mapConfig.setTimeToLiveSeconds(10);
mapConfig.setEvictionPolicy(EvictionPolicy.RANDOM);
HazelcastInstance hz = Hazelcast.newHazelcastInstance(config);
IMap<String, String> map = hz.getMap("myMap");
map.addEntryListener(new MyExpiredEntryListener(), true);
for (int i = 0; i < 100; i++) {
String uuid = UUID.randomUUID().toString();
map.put(uuid, uuid);
}
}
You will see the logs like below when running this implementation.
entry Expired EntryEvent{entryEventType=EXPIRED, member=Member [192.168.1.1]:5701 - ca76c6d8-abe0-4efe-a6a6-24330657675b this, name='myMap', key=70ee594c-ffea-4584-aefe-1148b9fcdf9f, oldValue=70ee594c-ffea-4584-aefe-1148b9fcdf9f, value=null, mergingValue=null}
Also, you can use other entry listeners according to your requirements.