void _setLowMemory(final ScheduledThreadPoolExecutor executor,
        final boolean isLowMemory,
        final long usedBytes,
        final InternalCache cache) {
      throw new IllegalStateException("subclass must override");
    }
Run all cancelation tasks. Leave the executor's task queue empty.
geode-core/src/main/java/org/apache/geode/cache/query/internal/QueryMonitor.java