Normal Description
Netty 4.x uses (Fast)ThreadLocal instances to provide a pool of (direct) buffers per thread (io.netty.buffer.PooledByteBufAllocator.PoolThreadLocalCache. However, these per-thread pools need to be cleaned up when a thread terminates (FastThreadLocal.removeAll()) - which is missing.
Although the possibility that such per-thread pools ever need to be cleaned up, since we rarely terminate threads, it still may actually happen and manifest in a late and hard to detect out-of-memory situation. One possibility to raise such a scenario is to regularly stop and restart the native protocol service.