[WIP][SYSTEMDS-3946] Merge PR Enable sending of large (>2GiB) FederatedRequests

src/main/java/org/apache/sysds/runtime/controlprogram/federated/FederatedChunkDecoder.java

@@ -0,0 +1,221 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.apache.sysds.runtime.controlprogram.federated;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.ObjectInputStream;
+import java.io.ObjectStreamClass;
+import java.nio.charset.StandardCharsets;
+import java.util.List;
+import java.util.concurrent.BlockingQueue;
+import java.util.concurrent.LinkedBlockingQueue;
+
+import org.apache.sysds.runtime.util.CommonThreadPool;
+
+import io.netty.buffer.ByteBuf;
+import io.netty.channel.ChannelHandlerContext;
+import io.netty.handler.codec.MessageToMessageDecoder;
+
+public class FederatedChunkDecoder extends MessageToMessageDecoder<ByteBuf> {
+	private static final Object END_OF_STREAM = new Object();
+	// stop reading at QUEUE_DEPTH, resume at half: gap avoids autoRead thrash
+	private static final int LOW_WATERMARK = FederatedChunkProtocol.QUEUE_DEPTH / 2;
+
+	private final BlockingQueue<Object> _payloads = new LinkedBlockingQueue<>();
+	private boolean _started;
+	private volatile boolean _throttled;
+
+	@Override
+	protected void decode(ChannelHandlerContext ctx, ByteBuf buf, List<Object> out) {
+		startReader(ctx);
+		byte type = buf.readByte();
+		int len = buf.readInt();
+		switch(type) {
+			case FederatedChunkProtocol.TYPE_DATA:
+				_payloads.add(readBytes(buf, len));
+				break;
+			case FederatedChunkProtocol.TYPE_END:
+				_payloads.add(END_OF_STREAM);
+				break;
+			case FederatedChunkProtocol.TYPE_ERROR:
+				_payloads.add(new IOException(buf.toString(buf.readerIndex(), len, StandardCharsets.UTF_8)));
+				break;
+			default:
+				_payloads.add(new IOException("Unknown federated chunk frame type: " + type));
+				break;
+		}
+		if(_payloads.size() >= FederatedChunkProtocol.QUEUE_DEPTH) {
+			_throttled = true;
+			ctx.channel().config().setAutoRead(false);
+		}
+	}
+
+	/**
+	 * Start the deserializer on a pool thread, at most once per channel.
+	 *
+	 * @param ctx handler context
+	 */
+	private void startReader(ChannelHandlerContext ctx) {
+		if(_started)
+			return;
+		_started = true;
+		CommonThreadPool.getDynamicPool().execute(() -> runDeserializer(ctx));
+	}
+
+	/**
+	 * Read one object from the queued payloads and fire it up the pipeline. A failure is fired as an exception on the
+	 * event loop instead.
+	 *
+	 * @param ctx handler context
+	 */
+	private void runDeserializer(ChannelHandlerContext ctx) {
+		try(ObjectInputStream ois = getObjectInputStream(new PayloadInputStream(this, ctx))) {
+			Object msg = ois.readObject();
+			ctx.channel().eventLoop().execute(() -> ctx.fireChannelRead(msg));
+		}
+		catch(Throwable t) {
+			ctx.channel().eventLoop().execute(() -> ctx.fireExceptionCaught(t));
+		}
+	}
+
+	/**
+	 * Take the next queued payload, blocking until one arrives.
+	 *
+	 * @return payload bytes, the end of stream marker or a queued failure
+	 * @throws InterruptedException on interrupt while the queue is empty
+	 */
+	private Object nextPayload() throws InterruptedException {
+		return _payloads.take();
+	}
+
+	/**
+	 * Re-enable channel reads once the payload queue has drained to the low watermark.
+	 *
+	 * @param ctx handler context
+	 */
+	private void resumeReadingIfDrained(ChannelHandlerContext ctx) {
+		if(_throttled && _payloads.size() <= LOW_WATERMARK) {
+			_throttled = false;
+			ctx.channel().eventLoop().execute(() -> ctx.channel().config().setAutoRead(true));
+		}
+	}
+
+	/**
+	 * Create an object input stream using the system class loader.
+	 *
+	 * @param in stream of payload bytes
+	 * @return object input stream
+	 * @throws IOException on stream header failure
+	 */
+	private static ObjectInputStream getObjectInputStream(InputStream in) throws IOException {
+		return new ObjectInputStream(in) {
+			@Override
+			protected Class<?> resolveClass(ObjectStreamClass desc) throws IOException, ClassNotFoundException {
+				try {
+					return Class.forName(desc.getName(), false, ClassLoader.getSystemClassLoader());
+				}
+				catch(ClassNotFoundException e) {
+					return super.resolveClass(desc);
+				}
+			}
+		};
+	}
+
+	private static byte[] readBytes(ByteBuf buf, int len) {
+		byte[] bytes = new byte[len];
+		buf.readBytes(bytes);
+		return bytes;
+	}
+
+	private static final class PayloadInputStream extends InputStream {
+		private static final byte[] EMPTY = new byte[0];
+
+		private final FederatedChunkDecoder _decoder;
+		private final ChannelHandlerContext _ctx;
+		private byte[] _current = EMPTY;
+		private int _pos;
+		private boolean _eof;
+
+		PayloadInputStream(FederatedChunkDecoder decoder, ChannelHandlerContext ctx) {
+			_decoder = decoder;
+			_ctx = ctx;
+		}
+
+		@Override
+		public int read() throws IOException {
+			if(!ensureCurrent())
+				return -1;
+			return _current[_pos++] & 0xff;
+		}
+
+		@Override
+		public int read(byte[] b, int off, int len) throws IOException {
+			if(!ensureCurrent())
+				return -1;
+			int n = Math.min(len, _current.length - _pos);
+			System.arraycopy(_current, _pos, b, off, n);
+			_pos += n;
+			return n;
+		}
+
+		/**
+		 * Advance to the next payload when the current one is exhausted. A queued failure is rethrown as an
+		 * IOException.
+		 *
+		 * @return true if bytes are available, false at end of stream
+		 * @throws IOException on a queued failure or on interrupt
+		 */
+		private boolean ensureCurrent() throws IOException {
+			while(_pos == _current.length) {
+				if(_eof)
+					return false;
+				Object next = take();
+				if(next == END_OF_STREAM) {
+					_eof = true;
+					return false;
+				}
+				if(next instanceof Throwable)
+					throw new IOException((Throwable) next);
+				_current = (byte[]) next;
+				_pos = 0;
+			}
+			return true;
+		}
+
+		/**
+		 * Take the next payload and resume reading if the queue has drained.
+		 *
+		 * @return payload bytes, the end of stream marker or a queued failure
+		 * @throws IOException on interrupt
+		 */
+		private Object take() throws IOException {
+			try {
+				Object next = _decoder.nextPayload();
+				_decoder.resumeReadingIfDrained(_ctx);
+				return next;
+			}
+			catch(InterruptedException e) {
+				Thread.currentThread().interrupt();
+				throw new IOException(e);
+			}
+		}
+	}
+}