09. Step-7. Listen to changes in the cache :: 2015/04/08 13:07

이제 cluster topology 변화에 대해서 어떻게 처리할 있는지 알게 되었다. 마찬가지로 cluster 내의  data 변화에 대해서도 처리할 있다. 이것이 어떻게 동작하는지 보여주기 위해서 2개의 node 역할을 분리할 것이다. Coordinator data put하고, 다른 node에서는 cache 변화된 내용을 보여줄 것이다.


@Listener(clustered = true)

public class CacheListener {

@CacheEntryCreated

public void entryCreated(CacheEntryCreatedEvent<String, LocationWeather> event) {

if (!event.isOriginLocal()) {

System.out.printf("-- Entry for %s modified by another node in the cluster\n", event.getKey());

}

}

}


일반적으로 cache listener 단지 "local events" 대해서만 listen 있다. 예를 들어, 동일 node에서 발생한 event 대해서만 listen 가능하다. 그러나, 이번 예제에서처럼 모든 node에서 발생한 event listen하고 싶다면 "clustered = true" annotation parameter 사용하여 모든 node event listen 있다.


Event notification 살펴보자.


git checkout -f step-7

mvn clean package exec:exec # from terminal 1

mvn exec:exec # from terminal 2


[Coordinator Output : PUT]

---- View changed: [hoth-1712] ----
---- Waiting for cluster to form ----
---- View changed: [hoth-1712, hoth-9822] ----
---- Fetching weather information ----
-- Entry for Rome, Italy modified by another node in the cluster
Rome, Italy - Temperature: 11.6° C, Conditions: Sky is Clear
Como, Italy - Temperature: 5.6° C, Conditions: Sky is Clear
-- Entry for Basel, Switzerland modified by another node in the cluster
Basel, Switzerland - Temperature: 2.9° C, Conditions: broken clouds
Bern, Switzerland - Temperature: -2.1° C, Conditions: scattered clouds
-- Entry for London, UK modified by another node in the cluster
London, UK - Temperature: 4.8° C, Conditions: light rain
-- Entry for Newcastle, UK modified by another node in the cluster
Newcastle, UK - Temperature: 1.8° C, Conditions: Sky is Clear
-- Entry for Bucharest, Romania modified by another node in the cluster
Bucharest, Romania - Temperature: 8.4° C, Conditions: few clouds
Cluj-Napoca, Romania - Temperature: 5.8° C, Conditions: broken clouds
-- Entry for Ottawa, Canada modified by another node in the cluster
Ottawa, Canada - Temperature: -12.3° C, Conditions: overcast clouds
-- Entry for Toronto, Canada modified by another node in the cluster
Toronto, Canada - Temperature: -10.1° C, Conditions: few clouds
Lisbon, Portugal - Temperature: 15.0° C, Conditions: light rain
-- Entry for Porto, Portugal modified by another node in the cluster
Porto, Portugal - Temperature: 12.1° C, Conditions: moderate rain
Raleigh, USA - Temperature: 6.0° C, Conditions: Sky is Clear
Washington, USA - Temperature: 3.5° C, Conditions: light rain
---- Fetched in 5466ms ----
---- Fetching weather information ----
Rome, Italy - Temperature: 11.6° C, Conditions: Sky is Clear
Como, Italy - Temperature: 5.6° C, Conditions: Sky is Clear
Basel, Switzerland - Temperature: 2.9° C, Conditions: broken clouds
Bern, Switzerland - Temperature: -2.1° C, Conditions: scattered clouds
London, UK - Temperature: 4.8° C, Conditions: light rain
Newcastle, UK - Temperature: 1.8° C, Conditions: Sky is Clear
Bucharest, Romania - Temperature: 8.4° C, Conditions: few clouds
Cluj-Napoca, Romania - Temperature: 5.8° C, Conditions: broken clouds
Ottawa, Canada - Temperature: -12.3° C, Conditions: overcast clouds
Toronto, Canada - Temperature: -10.1° C, Conditions: few clouds
Lisbon, Portugal - Temperature: 15.0° C, Conditions: light rain
Porto, Portugal - Temperature: 12.1° C, Conditions: moderate rain
Raleigh, USA - Temperature: 6.0° C, Conditions: Sky is Clear
Washington, USA - Temperature: 3.5° C, Conditions: light rain
---- Fetched in 2ms ----
---- Fetching weather information ----
-- Entry for Rome, Italy modified by another node in the cluster
Rome, Italy - Temperature: 11.6° C, Conditions: Sky is Clear
Como, Italy - Temperature: 5.6° C, Conditions: Sky is Clear
-- Entry for Basel, Switzerland modified by another node in the cluster
Basel, Switzerland - Temperature: 2.9° C, Conditions: broken clouds
Bern, Switzerland - Temperature: -2.1° C, Conditions: scattered clouds
-- Entry for London, UK modified by another node in the cluster
London, UK - Temperature: 4.8° C, Conditions: light rain
-- Entry for Newcastle, UK modified by another node in the cluster
Newcastle, UK - Temperature: 1.8° C, Conditions: Sky is Clear
-- Entry for Bucharest, Romania modified by another node in the cluster
Bucharest, Romania - Temperature: 8.4° C, Conditions: few clouds
Cluj-Napoca, Romania - Temperature: 5.8° C, Conditions: broken clouds
-- Entry for Ottawa, Canada modified by another node in the cluster
Ottawa, Canada - Temperature: -12.3° C, Conditions: overcast clouds
-- Entry for Toronto, Canada modified by another node in the cluster
Toronto, Canada - Temperature: -10.1° C, Conditions: few clouds
Lisbon, Portugal - Temperature: 15.0° C, Conditions: light rain
-- Entry for Porto, Portugal modified by another node in the cluster
Porto, Portugal - Temperature: 12.1° C, Conditions: moderate rain
Raleigh, USA - Temperature: 6.0° C, Conditions: Sky is Clear
Washington, USA - Temperature: 3.5° C, Conditions: light rain
---- Fetched in 1248ms ----


[Other Output : Event View]


---- View changed: [hoth-1712, hoth-9822] ----
---- Waiting for cluster to form ----
-- Entry for Rome, Italy modified by another node in the cluster
-- Entry for Como, Italy modified by another node in the cluster
-- Entry for Basel, Switzerland modified by another node in the cluster
-- Entry for Bern, Switzerland modified by another node in the cluster
-- Entry for London, UK modified by another node in the cluster
-- Entry for Newcastle, UK modified by another node in the cluster
-- Entry for Bucharest, Romania modified by another node in the cluster
-- Entry for Cluj-Napoca, Romania modified by another node in the cluster
-- Entry for Ottawa, Canada modified by another node in the cluster
-- Entry for Toronto, Canada modified by another node in the cluster
-- Entry for Lisbon, Portugal modified by another node in the cluster
-- Entry for Porto, Portugal modified by another node in the cluster
-- Entry for Raleigh, USA modified by another node in the cluster
-- Entry for Washington, USA modified by another node in the cluster
-- Entry for Rome, Italy modified by another node in the cluster
-- Entry for Como, Italy modified by another node in the cluster
-- Entry for Basel, Switzerland modified by another node in the cluster
-- Entry for Bern, Switzerland modified by another node in the cluster
-- Entry for London, UK modified by another node in the cluster
-- Entry for Newcastle, UK modified by another node in the cluster
-- Entry for Bucharest, Romania modified by another node in the cluster
-- Entry for Cluj-Napoca, Romania modified by another node in the cluster
-- Entry for Ottawa, Canada modified by another node in the cluster
-- Entry for Toronto, Canada modified by another node in the cluster
-- Entry for Lisbon, Portugal modified by another node in the cluster
-- Entry for Porto, Portugal modified by another node in the cluster
-- Entry for Raleigh, USA modified by another node in the cluster
-- Entry for Washington, USA modified by another node in the cluster
---- View changed: [hoth-9822] ----


실제로 cache 작업을 수행하는 coordinator에서 남기는 event log another node에서 entrries 수정되었음을 알리는 event log 있을 것이다. 이것은 consistent hashing algorithm 의해서 entry 어느 node 원본이 저장되어 있는지를 설명한다. 다음 단계에서는 분산에 대해 어떻게 제어할 있는지에 대해서 설명할 것이다.

2015/04/08 13:07 2015/04/08 13:07
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