/**
* Copyright 2015 Otto (GmbH & Co KG)
*
* 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.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.ottogroup.bi.spqr.websocket.server;
import static io.netty.handler.codec.http.HttpHeaders.Names.HOST;
import static io.netty.handler.codec.http.HttpMethod.GET;
import static io.netty.handler.codec.http.HttpResponseStatus.BAD_REQUEST;
import static io.netty.handler.codec.http.HttpResponseStatus.FORBIDDEN;
import static io.netty.handler.codec.http.HttpVersion.HTTP_1_1;
import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelFutureListener;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
import io.netty.handler.codec.http.DefaultFullHttpResponse;
import io.netty.handler.codec.http.FullHttpRequest;
import io.netty.handler.codec.http.FullHttpResponse;
import io.netty.handler.codec.http.HttpHeaders;
import io.netty.handler.codec.http.HttpResponse;
import io.netty.handler.codec.http.websocketx.CloseWebSocketFrame;
import io.netty.handler.codec.http.websocketx.TextWebSocketFrame;
import io.netty.handler.codec.http.websocketx.WebSocketFrame;
import io.netty.handler.codec.http.websocketx.WebSocketServerHandshaker;
import io.netty.handler.codec.http.websocketx.WebSocketServerHandshakerFactory;
import io.netty.util.CharsetUtil;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import org.apache.commons.lang3.StringUtils;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.ottogroup.bi.spqr.websocket.kafka.KafkaTopicRequest;
import com.ottogroup.bi.spqr.websocket.kafka.KafkaTopicWebSocketEmitter;
/**
* Receives incoming connections and binds them to {@link KafkaTopicWebSocketEmitter}
* @author mnxfst
* @since Apr 17, 2015
*/
public class SPQRWebSocketServerHandler extends SimpleChannelInboundHandler<Object> {
private static final String WEBSOCKET_PATH = "/pipeline";
private final ObjectMapper jsonMapper = new ObjectMapper();
private KafkaTopicWebSocketEmitter emitter = null;
private WebSocketServerHandshaker handshaker = null;
private ExecutorService executorService = Executors.newCachedThreadPool();
/**
* @see io.netty.channel.SimpleChannelInboundHandler#channelRead0(io.netty.channel.ChannelHandlerContext, java.lang.Object)
*/
protected void channelRead0(ChannelHandlerContext ctx, Object msg) throws Exception {
if(msg instanceof WebSocketFrame) {
handleWebSocketFrame(ctx, (WebSocketFrame)msg);
} else {
handleHttpRequest(ctx, (FullHttpRequest) msg);
}
}
private void handleWebSocketFrame(ChannelHandlerContext ctx, WebSocketFrame frame) {
// if client request to close socket connection: shut it down ;-)
if (frame instanceof CloseWebSocketFrame) {
handshaker.close(ctx.channel(), (CloseWebSocketFrame) frame.retain());
return;
}
// not of expected type: return an error
if (!(frame instanceof TextWebSocketFrame)) {
throw new UnsupportedOperationException(String.format("%s frame types not supported", frame.getClass()
.getName()));
}
// only the first request is forwarded to the kafka topic emitter. if the client wishes to change
// the topic a new connection must be established - connection migration is not supported by now
// TODO add support for connection migration
if(this.emitter == null) {
// extract content from request and ensure that it is neither null nor empty
String requestContent = ((TextWebSocketFrame) frame).text();
if(StringUtils.isBlank(requestContent)) {
ctx.channel().writeAndFlush("Invalid request received. Please see documentation for further infromation");
return;
}
// convert content into topic request representation and check if it contains a non-null and non-empty topic identifier
KafkaTopicRequest topicRequest = null;
try {
topicRequest = this.jsonMapper.readValue(requestContent, KafkaTopicRequest.class);
} catch(Exception e) {
ctx.channel().writeAndFlush(new TextWebSocketFrame(Unpooled.copiedBuffer("Invalid request format. Please see document for further information".getBytes())));
return;
}
if(StringUtils.isBlank(topicRequest.getTopicId())) {
ctx.channel().writeAndFlush(new TextWebSocketFrame(Unpooled.copiedBuffer("Invalid request, missing topic identifier. Please see document for further information".getBytes())));
return;
}
// establish connection with kafka topic and start emitting content to websocket
this.emitter = new KafkaTopicWebSocketEmitter(ctx.channel(), 1024, executorService, "localhost:2181", "client-id-"+System.currentTimeMillis(), topicRequest.getTopicId());
executorService.submit(this.emitter);
}
}
/**
* @see io.netty.channel.ChannelHandlerAdapter#handlerRemoved(io.netty.channel.ChannelHandlerContext)
*/
public void handlerRemoved(ChannelHandlerContext ctx) throws Exception {
// shutdown the emitter if one is available
if(this.emitter != null)
this.emitter.shutdown();
// shutdown runtime environment
this.executorService.shutdownNow();
}
/**
* Handles incoming http request pointing. Parts of the code were copied from {@linkplain http://netty.io} web socket server example.
* The origins may be found at: {@linkplain https://github.com/netty/netty/blob/4.0/example/src/main/java/io/netty/example/http/websocketx/server/WebSocketServerHandler.java}
* @param ctx
* @param req
*/
private void handleHttpRequest(ChannelHandlerContext ctx, FullHttpRequest req) {
// handle bad requests as indicated by decoder
if (!req.getDecoderResult().isSuccess()) {
sendHttpResponse(ctx, req, new DefaultFullHttpResponse(HTTP_1_1, BAD_REQUEST));
return;
}
// allow only GET methods to comply with REST spec as this is not about modifying content
// but receiving it ;-)
if (req.getMethod() != GET) {
sendHttpResponse(ctx, req, new DefaultFullHttpResponse(HTTP_1_1, FORBIDDEN));
return;
}
// Handshake
String wsLocation = "ws://" + req.headers().get(HOST) + WEBSOCKET_PATH;
WebSocketServerHandshakerFactory wsFactory = new WebSocketServerHandshakerFactory(
wsLocation, null, true);
handshaker = wsFactory.newHandshaker(req);
if (handshaker == null) {
WebSocketServerHandshakerFactory.sendUnsupportedVersionResponse(ctx.channel());
} else {
handshaker.handshake(ctx.channel(), req);
}
}
/**
* Sends a {@link HttpResponse} according to prepared {@link FullHttpResponse} to the client. The
* code was copied from netty.io websocket server example. The origins may be found at:
* {@linkplain https://github.com/netty/netty/blob/4.0/example/src/main/java/io/netty/example/http/websocketx/server/WebSocketServerHandler.java}
* @param ctx
* @param req
* @param res
*/
private void sendHttpResponse(ChannelHandlerContext ctx, FullHttpRequest req, FullHttpResponse res) {
// Generate an error page if response getStatus code is not OK (200).
if (res.getStatus().code() != 200) {
ByteBuf buf = Unpooled.copiedBuffer(res.getStatus().toString(), CharsetUtil.UTF_8);
res.content().writeBytes(buf);
buf.release();
HttpHeaders.setContentLength(res, res.content().readableBytes());
}
// Send the response and close the connection if necessary.
ChannelFuture f = ctx.channel().writeAndFlush(res);
if(!HttpHeaders.isKeepAlive(req) || res.getStatus().code() != 200) {
f.addListener(ChannelFutureListener.CLOSE);
}
}
}