public List<String> getMissingColocatedChildren() {
    ColocationLogger colocationLogger = missingColocatedRegionLogger.get();
    if (colocationLogger != null) {
      return colocationLogger.updateAndGetMissingChildRegions();
    }
    return Collections.emptyList();
  }
Returns existing ColocationLogger or creates and sets a new instance if one does not yet exist.
Spins to ensure that if another thread sets ColocationLogger, we return that one instead of
setting another instance. Checks CancelCriterion during spin and either returns an instance or
throws NullPointerException. The only way to exist the loop is with an instance or by throwing
CancelException if the Cache closes.
geode-core/src/main/java/org/apache/geode/internal/cache/PartitionedRegion.java