Java tutorial
/** * Copyright 2016 LinkedIn Corp. All rights reserved. * * Licensed 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. */ package com.github.ambry.rest; import com.github.ambry.router.AsyncWritableChannel; import com.github.ambry.router.Callback; import com.github.ambry.router.FutureResult; import io.netty.handler.codec.http.CookieDecoder; import io.netty.handler.codec.http.HttpContent; import io.netty.handler.codec.http.HttpHeaders; import io.netty.handler.codec.http.HttpMethod; import io.netty.handler.codec.http.HttpRequest; import io.netty.handler.codec.http.LastHttpContent; import io.netty.handler.codec.http.QueryStringDecoder; import io.netty.handler.codec.http.multipart.HttpPostRequestDecoder; import io.netty.util.ReferenceCountUtil; import java.nio.ByteBuffer; import java.nio.channels.ClosedChannelException; import java.util.Collections; import java.util.HashSet; import java.util.List; import java.util.Map; import java.util.Queue; import java.util.Set; import java.util.TreeMap; import java.util.concurrent.Future; import java.util.concurrent.LinkedBlockingQueue; import java.util.concurrent.atomic.AtomicBoolean; import java.util.concurrent.atomic.AtomicLong; import java.util.concurrent.locks.ReentrantLock; import javax.servlet.http.Cookie; import org.slf4j.Logger; import org.slf4j.LoggerFactory; /** * Netty specific implementation of {@link RestRequest}. * <p/> * A wrapper over {@link HttpRequest} and all the {@link HttpContent} associated with the request. */ class NettyRequest implements RestRequest { private static final ClosedChannelException CLOSED_CHANNEL_EXCEPTION = new ClosedChannelException(); protected final HttpRequest request; protected final NettyMetrics nettyMetrics; protected final Map<String, Object> allArgs = new TreeMap<String, Object>(String.CASE_INSENSITIVE_ORDER); protected final Queue<HttpContent> requestContents = new LinkedBlockingQueue<HttpContent>(); protected final ReentrantLock contentLock = new ReentrantLock(); protected volatile ReadIntoCallbackWrapper callbackWrapper = null; protected volatile Map<String, Object> allArgsReadOnly = null; private final long size; private final QueryStringDecoder query; private final RestMethod restMethod; private final RestRequestMetricsTracker restRequestMetricsTracker = new RestRequestMetricsTracker(); private final AtomicBoolean channelOpen = new AtomicBoolean(true); private final AtomicLong bytesReceived = new AtomicLong(0); private final Logger logger = LoggerFactory.getLogger(getClass()); private volatile AsyncWritableChannel writeChannel = null; private volatile Exception channelException = CLOSED_CHANNEL_EXCEPTION; protected static String MULTIPLE_HEADER_VALUE_DELIMITER = ", "; /** * Wraps the {@code request} in an implementation of {@link RestRequest} so that other layers can understand the * request. * <p/> * Note on content size: The content size is deduced in the following order:- * 1. From the {@link RestUtils.Headers#BLOB_SIZE} header. * 2. If 1 fails, from the {@link HttpHeaders.Names#CONTENT_LENGTH} header. * 3. If 2 fails, it is set to -1 which means that the content size is unknown. * If content size is set in the header (i.e. not -1), the actual content size should match that value. Otherwise, an * exception will be thrown. * @param request the {@link HttpRequest} that needs to be wrapped. * @param nettyMetrics the {@link NettyMetrics} instance to use. * @throws IllegalArgumentException if {@code request} is null. * @throws RestServiceException if the {@link HttpMethod} defined in {@code request} is not recognized as a * {@link RestMethod}. */ public NettyRequest(HttpRequest request, NettyMetrics nettyMetrics) throws RestServiceException { if (request == null) { throw new IllegalArgumentException("Received null HttpRequest"); } restRequestMetricsTracker.nioMetricsTracker.markRequestReceived(); HttpMethod httpMethod = request.getMethod(); if (httpMethod == HttpMethod.GET) { restMethod = RestMethod.GET; } else if (httpMethod == HttpMethod.POST) { restMethod = RestMethod.POST; } else if (httpMethod == HttpMethod.DELETE) { restMethod = RestMethod.DELETE; } else if (httpMethod == HttpMethod.HEAD) { restMethod = RestMethod.HEAD; } else { nettyMetrics.unsupportedHttpMethodError.inc(); throw new RestServiceException("http method not supported: " + httpMethod, RestServiceErrorCode.UnsupportedHttpMethod); } this.request = request; this.query = new QueryStringDecoder(request.getUri()); this.nettyMetrics = nettyMetrics; if (HttpHeaders.getHeader(request, RestUtils.Headers.BLOB_SIZE, null) != null) { size = Long.parseLong(HttpHeaders.getHeader(request, RestUtils.Headers.BLOB_SIZE)); } else { size = HttpHeaders.getContentLength(request, -1); } // query params. for (Map.Entry<String, List<String>> e : query.parameters().entrySet()) { StringBuilder value = null; if (e.getValue() != null) { StringBuilder combinedValues = combineVals(new StringBuilder(), e.getValue()); if (combinedValues.length() > 0) { value = combinedValues; } } allArgs.put(e.getKey(), value); } Set<io.netty.handler.codec.http.Cookie> nettyCookies = null; // headers. for (Map.Entry<String, String> e : request.headers()) { StringBuilder sb; if (e.getKey().equals(HttpHeaders.Names.COOKIE)) { String value = e.getValue(); if (value != null) { nettyCookies = CookieDecoder.decode(value); } } else { boolean valueNull = request.headers().get(e.getKey()) == null; if (!valueNull && allArgs.get(e.getKey()) == null) { sb = new StringBuilder(e.getValue()); allArgs.put(e.getKey(), sb); } else if (!valueNull) { sb = (StringBuilder) allArgs.get(e.getKey()); sb.append(MULTIPLE_HEADER_VALUE_DELIMITER).append(e.getValue()); } else if (!allArgs.containsKey(e.getKey())) { allArgs.put(e.getKey(), null); } } } // turn all StringBuilders into String for (Map.Entry<String, Object> e : allArgs.entrySet()) { if (allArgs.get(e.getKey()) != null) { allArgs.put(e.getKey(), (e.getValue()).toString()); } } // add cookies to the args as java cookies if (nettyCookies != null) { Set<javax.servlet.http.Cookie> cookies = convertHttpToJavaCookies(nettyCookies); allArgs.put(RestUtils.Headers.COOKIE, cookies); } allArgsReadOnly = Collections.unmodifiableMap(allArgs); } @Override public String getUri() { return request.getUri(); } @Override public String getPath() { return query.path(); } @Override public RestMethod getRestMethod() { return restMethod; } @Override public Map<String, Object> getArgs() { return allArgsReadOnly; } @Override public void prepare() throws RestServiceException { // no op. } @Override public boolean isOpen() { return channelOpen.get(); } @Override public void close() { if (channelOpen.compareAndSet(true, false)) { contentLock.lock(); try { logger.trace("Closing NettyRequest {} with {} content chunks unread", getUri(), requestContents.size()); // For non-POST we usually have one content chunk unread - this the LastHttpContent chunk. This is OK. HttpContent content = requestContents.poll(); while (content != null) { ReferenceCountUtil.release(content); content = requestContents.poll(); } } finally { contentLock.unlock(); restRequestMetricsTracker.recordMetrics(); if (callbackWrapper != null) { callbackWrapper.invokeCallback(channelException); } } } } @Override public RestRequestMetricsTracker getMetricsTracker() { return restRequestMetricsTracker; } /** * Only prints the request metadata (URI, path, HTTP method etc) as a string. Does not print the content. * @return the request metadata (URI, path, HTTP method etc) as a String. Content is *not* included. */ @Override public String toString() { return request.toString(); } /** * Returns the value of the ambry specific content length header ({@link RestUtils.Headers#BLOB_SIZE}. If there is * no such header, returns length in the "Content-Length" header. If there is no such header, tries to infer content * size. If that cannot be done, returns 0. * <p/> * This function does not individually count the bytes in the content (it is not possible) so the bytes received may * actually be different if the stream is buggy or the client made a mistake. Do *not* treat this as fully accurate. * @return the size of content as defined in headers. Might not be actual length of content if the stream is buggy. */ @Override public long getSize() { return size; } @Override public Future<Long> readInto(AsyncWritableChannel asyncWritableChannel, Callback<Long> callback) { ReadIntoCallbackWrapper tempWrapper = new ReadIntoCallbackWrapper(callback); contentLock.lock(); try { if (!isOpen()) { nettyMetrics.requestAlreadyClosedError.inc(); tempWrapper.invokeCallback(new ClosedChannelException()); } else if (writeChannel != null) { throw new IllegalStateException("ReadableStreamChannel cannot be read more than once"); } HttpContent content = requestContents.poll(); while (content != null) { try { writeContent(asyncWritableChannel, tempWrapper, content); } finally { ReferenceCountUtil.release(content); } content = requestContents.poll(); } callbackWrapper = tempWrapper; writeChannel = asyncWritableChannel; } finally { contentLock.unlock(); } return tempWrapper.futureResult; } /** * Adds some content in the form of {@link HttpContent} to this RestRequest. This content will be available to read * through the read operations. * @param httpContent the {@link HttpContent} that needs to be added. * @throws IllegalStateException if content is being added when it is not expected (GET, DELETE, HEAD). * @throws RestServiceException if request channel has been closed. */ protected void addContent(HttpContent httpContent) throws RestServiceException { if (!getRestMethod().equals(RestMethod.POST) && (!(httpContent instanceof LastHttpContent) || httpContent.content().readableBytes() > 0)) { throw new IllegalStateException("There is no content expected for " + getRestMethod()); } else { validateState(httpContent); contentLock.lock(); try { if (!isOpen()) { nettyMetrics.requestAlreadyClosedError.inc(); throw new RestServiceException("The request has been closed and is not accepting content", RestServiceErrorCode.RequestChannelClosed); } else if (writeChannel != null) { writeContent(writeChannel, callbackWrapper, httpContent); } else { requestContents.add(ReferenceCountUtil.retain(httpContent)); } } finally { contentLock.unlock(); } } } /** * Provides info on whether this request desires keep-alive or not. * @return {@code true} if keep-alive. {@code false} otherwise. */ protected boolean isKeepAlive() { return HttpHeaders.isKeepAlive(request); } /** * Provides info on whether this request is multipart or not. * @return {@code true} if multipart. {@code false} otherwise. */ protected boolean isMultipart() { return HttpPostRequestDecoder.isMultipart(request); } /** * Writes the data in the provided {@code httpContent} to the given {@code writeChannel}. * @param writeChannel the {@link AsyncWritableChannel} to write the data of {@code httpContent} to. * @param callbackWrapper the {@link ReadIntoCallbackWrapper} for the read operation. * @param httpContent the piece of {@link HttpContent} that needs to be written to the {@code writeChannel}. */ protected void writeContent(AsyncWritableChannel writeChannel, ReadIntoCallbackWrapper callbackWrapper, HttpContent httpContent) { boolean retained = false; ByteBuffer[] contentBuffers; Callback<Long>[] writeCallbacks; // LastHttpContent in the end marker in netty http world. boolean isLast = httpContent instanceof LastHttpContent; if (httpContent.content().nioBufferCount() > 0) { // not a copy. httpContent = ReferenceCountUtil.retain(httpContent); retained = true; contentBuffers = httpContent.content().nioBuffers(); writeCallbacks = new ContentWriteCallback[contentBuffers.length]; int i = 0; for (; i < contentBuffers.length - 1; i++) { writeCallbacks[i] = new ContentWriteCallback(null, false, callbackWrapper); } writeCallbacks[i] = new ContentWriteCallback(httpContent, isLast, callbackWrapper); } else { // this will not happen (looking at current implementations of ByteBuf in Netty), but if it does, we cannot avoid // a copy (or we can introduce a read(GatheringByteChannel) method in ReadableStreamChannel if required). nettyMetrics.contentCopyCount.inc(); logger.warn("HttpContent had to be copied because ByteBuf did not have a backing ByteBuffer"); ByteBuffer contentBuffer = ByteBuffer.allocate(httpContent.content().readableBytes()); httpContent.content().readBytes(contentBuffer); // no need to retain httpContent since we have a copy. ContentWriteCallback writeCallback = new ContentWriteCallback(null, isLast, callbackWrapper); contentBuffers = new ByteBuffer[] { contentBuffer }; writeCallbacks = new ContentWriteCallback[] { writeCallback }; } boolean asyncWritesCalled = false; try { for (int i = 0; i < contentBuffers.length; i++) { writeChannel.write(contentBuffers[i], writeCallbacks[i]); } asyncWritesCalled = true; } finally { if (retained && !asyncWritesCalled) { ReferenceCountUtil.release(httpContent); } } } /** * Converts the Set of {@link javax.servlet.http.Cookie}s to equivalent {@link javax.servlet.http.Cookie}s * @param httpCookies Set of {@link javax.servlet.http.Cookie}s that needs to be converted * @return Set of {@link javax.servlet.http.Cookie}s equivalent to the passed in {@link javax.servlet.http.Cookie}s */ private Set<Cookie> convertHttpToJavaCookies(Set<io.netty.handler.codec.http.Cookie> httpCookies) { Set<javax.servlet.http.Cookie> cookies = new HashSet<Cookie>(); for (io.netty.handler.codec.http.Cookie cookie : httpCookies) { javax.servlet.http.Cookie javaCookie = new javax.servlet.http.Cookie(cookie.getName(), cookie.getValue()); cookies.add(javaCookie); } return cookies; } /** * Combines {@code values} into {@code currValue} by creating a comma seperated string. * @param currValue the value to which {@code values} have to be appeneded to. * @param values the values that need to be appended to @code currValue}. * @return the updated @code currValue}. */ private StringBuilder combineVals(StringBuilder currValue, List<String> values) { for (String value : values) { if (currValue.length() > 0) { currValue.append(MULTIPLE_HEADER_VALUE_DELIMITER); } currValue.append(value); } return currValue; } /** * Validates the stream by checking that the size in the headers matches the size of the actual data. * @param httpContent the {@link HttpContent} that was just received. * @throws RestServiceException if {@code httpContent} is the last piece of content and the size of data does * not match the size in the header. */ private void validateState(HttpContent httpContent) throws RestServiceException { long bytesReceivedTillNow = bytesReceived.addAndGet(httpContent.content().readableBytes()); if (size > 0) { if (bytesReceivedTillNow > size) { channelException = new RestServiceException( "Size of content is more than the size provided in headers", RestServiceErrorCode.BadRequest); throw (RestServiceException) channelException; } else if (httpContent instanceof LastHttpContent && bytesReceivedTillNow != size) { channelException = new RestServiceException( "Size of content is less than the size provided in headers", RestServiceErrorCode.BadRequest); throw (RestServiceException) channelException; } } } } /** * Callback for each write into the given {@link AsyncWritableChannel}. */ class ContentWriteCallback implements Callback<Long> { private final HttpContent httpContent; private final boolean isLast; private final ReadIntoCallbackWrapper callbackWrapper; /** * Creates a new instance of ContentWriteCallback. * @param httpContent the {@link HttpContent} whose bytes were just written. Should be null if the data from the * original {@link HttpContent} was copied and not "retained". * @param isLast if this is the last piece of {@link HttpContent} for this request. * @param callbackWrapper the {@link ReadIntoCallbackWrapper} that will receive updates of bytes read and one that * should be invoked in {@link #onCompletion(Long, Exception)} if {@code isLast} is * {@code true} or exception passed is not null. */ public ContentWriteCallback(HttpContent httpContent, boolean isLast, ReadIntoCallbackWrapper callbackWrapper) { this.httpContent = httpContent; this.isLast = isLast; this.callbackWrapper = callbackWrapper; } /** * Decreases reference counts of content if required, updates the number of bytes read and invokes * {@link ReadIntoCallbackWrapper#invokeCallback(Exception)} if {@code exception} is not {@code null} or if this is * the last piece of content in the request. * @param result The result of the request. This would be non null when the request executed successfully * @param exception The exception that was reported on execution of the request */ @Override public void onCompletion(Long result, Exception exception) { if (httpContent != null) { ReferenceCountUtil.release(httpContent); } callbackWrapper.updateBytesRead(result); if (exception != null || isLast) { callbackWrapper.invokeCallback(exception); } } } /** * Wrapper for callbacks provided to {@link NettyRequest#readInto(AsyncWritableChannel, Callback)}. */ class ReadIntoCallbackWrapper { /** * The {@link Future} where the result of {@link NettyRequest#readInto(AsyncWritableChannel, Callback)} will * eventually be updated. */ public final FutureResult<Long> futureResult = new FutureResult<Long>(); private final Callback<Long> callback; private final AtomicLong totalBytesRead = new AtomicLong(0); private final AtomicBoolean callbackInvoked = new AtomicBoolean(false); /** * Creates an instance of ReadIntoCallbackWrapper with the given {@code callback}. * @param callback the {@link Callback} to invoke on operation completion. */ public ReadIntoCallbackWrapper(Callback<Long> callback) { this.callback = callback; } /** * Updates the number of bytes that have been successfully read into the given {@link AsyncWritableChannel}. * @param delta the number of bytes read in the current invocation. * @return the total number of bytes read until now. */ public long updateBytesRead(long delta) { return totalBytesRead.addAndGet(delta); } /** * Invokes the callback and updates the future once this is called. This function ensures that the callback is invoked * just once. * @param exception the {@link Exception}, if any, to pass to the callback. */ public void invokeCallback(Exception exception) { if (callbackInvoked.compareAndSet(false, true)) { futureResult.done(totalBytesRead.get(), exception); if (callback != null) { callback.onCompletion(totalBytesRead.get(), exception); } } } }