boolean shouldProceed(ResourceEvent event) {
    InternalDistributedSystem.getConnectedInstance();

    // CACHE_REMOVE is a special event. ForcedDisconnectException may raise this event.
    if (!system.isConnected() && !event.equals(ResourceEvent.CACHE_REMOVE)) {
      return false;
    }

    InternalCache currentCache = system.getCache();
    if (currentCache == null) {
      return false;
    }
    return !currentCache.isClosed();
  }
Checks various conditions which might arise due to race condition for lock of
GemFireCacheImpl.class which is obtained while GemFireCacheImpl constructor, cache.close(),
DistributedSystem.disconnect().

As ManagementService creation logic is called in cache.init() method it leaves a small window
of loosing the lock of GemFireCacheImpl.class

These checks ensures that something unwanted has not happened during that small window

@return true or false depending on the status of Cache and System
geode-core/src/main/java/org/apache/geode/management/internal/beans/ManagementListener.java