presto-main/src/main/java/io/prestosql/memory/ClusterMemoryManager.java/ClusterMemoryManager/addChangeListener
class ClusterMemoryManager:    @Override
    public synchronized void addChangeListener(MemoryPoolId poolId, Consumer<MemoryPoolInfo> listener)
    {
        verify(memoryPoolExists(poolId), "Memory pool does not exist: %s", poolId);
        changeListeners.computeIfAbsent(poolId, id -> new ArrayList<>()).add(listener);
    }