@Override
    public void memberDeparted(DistributionManager distributionManager,
        InternalDistributedMember id, boolean crashed) {
      if (logger.isDebugEnabled()) {
        logger.debug("Observer for bucket {} member departed {}", bucketToMonitor, id);
      }
      synchronized (this) {
        departures.getAndSet(true);
        notifyAll();
      }
    }
Monitors distributed membership for a given bucket
geode-core/src/main/java/org/apache/geode/internal/cache/PRHARedundancyProvider.java