you may suffer from OOM when we are using
public static final ByteBufAllocator byteBufAllocator =
UnpooledByteBufAllocator.DEFAULT;
and configure your Encoder as “preferDirect = false”, so you are using
HeapBuf for encoding.
public class NettyProtocolEncoder extends MessageToByteEncoder<Object> {
public NettyProtocolEncoder() {
super(false);
}
the problem is caused by the code below
protected final Object filterOutboundMessage(Object msg) {
if (msg instanceof ByteBuf) {
ByteBuf buf = (ByteBuf) msg;
if (buf.isDirect()) {
return msg;
}
return newDirectBuffer(buf);
}
if (msg instanceof FileRegion) {
return msg;
}
throw new UnsupportedOperationException(
"unsupported message type: " +
StringUtil.simpleClassName(msg) + EXPECTED_TYPES);
}
static final class ThreadLocalDirectByteBuf extends UnpooledDirectByteBuf {
private static final Recycler<ThreadLocalDirectByteBuf>
RECYCLER = new Recycler<ThreadLocalDirectByteBuf>() {
@Override
protected ThreadLocalDirectByteBuf newObject(Handle handle) {
return new ThreadLocalDirectByteBuf(handle);
}
};
static ThreadLocalDirectByteBuf newInstance() {
ThreadLocalDirectByteBuf buf = RECYCLER.get();
buf.setRefCnt(1);
return buf;
}
private final Handle handle;
private ThreadLocalDirectByteBuf(Handle handle) {
super(UnpooledByteBufAllocator.DEFAULT, 256, Integer.MAX_VALUE);
this.handle = handle;
}
@Override
protected void deallocate() {
if (capacity() > THREAD_LOCAL_BUFFER_SIZE) {
super.deallocate();
} else {
clear();
RECYCLER.recycle(this, handle);
}
}
}
- netty tried to convert the HeapBuf into a DirectBuf
(filterOutboundMessage method)。The DirectBuf is retrieved from RECYCLER
- RECYCLER may hold a large amount of ThreadLocalDirectByteBuf.
- RECYCLER is not used to retrieve buffer when reading data. Attempts to
allocate DirectBuffer may trigger FullGC
- your peer could be in the same situation. so both side get blocked.
i’m wondering why we are not using RECYCLER when reading data ;)
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