前言
Dubbo3开始支持在单个端口上监听多个协议的不同服务。 比如使用Triple协议启动端口复用后,可以在相同的端口上为服务增加 Dubbo协议支持,以及Qos协议支持。
这些协议的识别都是由一个统一的端口复用服务器进行处理的,可以用于服务的协议迁移,并且可以节约端口以及相关的资源,减少运维的复杂性。
NettyPortUnificationServer
开启端口复用后,Dubbo服务启动时默认会启动NettyPortUnificationServer
,它在doOpen()
方法里会启动ServerBootstrap,对于新连接的ChannelPipeline只添加了一个NettyPortUnificationServerHandler,用于协议检测。
java
protected void initChannel(SocketChannel ch) throws Exception {
final ChannelPipeline p = ch.pipeline();
final NettyPortUnificationServerHandler puHandler;
// 端口统一处理器 多协议服务复用单个端口
puHandler = new NettyPortUnificationServerHandler(getUrl(), sslContext, true, getProtocols(),
NettyPortUnificationServer.this, NettyPortUnificationServer.this.dubboChannels,
getSupportedUrls(), getSupportedHandlers());
p.addLast("negotiation-protocol", puHandler);
}
因为一个端口要对外提供多协议服务,在连接没有建立前,服务端也不知道客户端到底使用哪种协议,此时也无法过多的配置ChannelPipeline,只能先添加一个协议检测的Handler,后续确认具体协议后,再针对性的配置ChannelPipeline,并且把当前协议检测的Handler移除。
NettyPortUnificationServerHandler
该处理器的主要职责是:检测客户端使用的协议、针对性的配置ChannelPipeline、移除协议检测Handler。
它继承自ByteToMessageDecoder
,具备解码器的能力,它会在decode()
检测协议。
绝大多数协议都会在报文的前几个字节带上一个魔数、或者发送一个魔法字符串,作为协议的标识。例如Dubbo协议的魔数是0xdabb
,HTTP2协议会发送一个魔法字符串PRI * HTTP/2.0\r\n\r\nSM\r\n\r\n
。
Dubbo正是基于此来实现协议检测的。
java
protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out)
throws Exception {
NettyChannel channel = NettyChannel.getOrAddChannel(ctx.channel(), url, handler);
if (in.readableBytes() < 2) {
return;
}
if (isSsl(in)) {
enableSsl(ctx);
} else {
for (final WireProtocol protocol : protocols) {
in.markReaderIndex();
ChannelBuffer buf = new NettyBackedChannelBuffer(in);
/**
* 协议检测 通过魔法前缀
* dubbo > 0xdabb
* triple > PRI * HTTP/2.0\r\n\r\nSM\r\n\r\n
*/
final ProtocolDetector.Result result = protocol.detector().detect(buf);
in.resetReaderIndex();
switch (result) {
case UNRECOGNIZED:
continue;
case RECOGNIZED:
String protocolName = url.getOrDefaultFrameworkModel().getExtensionLoader(WireProtocol.class)
.getExtensionName(protocol);
ChannelHandler localHandler = this.handlerMapper.getOrDefault(protocolName, handler);
URL localURL = this.urlMapper.getOrDefault(protocolName, url);
channel.setUrl(localURL);
NettyConfigOperator operator = new NettyConfigOperator(channel, localHandler);
protocol.configServerProtocolHandler(url, operator);
ctx.pipeline().remove(this);// 协议一旦确认 当前Handler就没用了
case NEED_MORE_DATA:
return;
default:
return;
}
}
byte[] preface = new byte[in.readableBytes()];
in.readBytes(preface);
Set<String> supported = url.getApplicationModel()
.getExtensionLoader(WireProtocol.class)
.getSupportedExtensions();
LOGGER.error(INTERNAL_ERROR, "unknown error in remoting module", "", String.format("Can not recognize protocol from downstream=%s . "
+ "preface=%s protocols=%s", ctx.channel().remoteAddress(),
Bytes.bytes2hex(preface),
supported));
in.clear();
ctx.close();
}
}
ProtocolDetector
协议检测的规则交给了org.apache.dubbo.remoting.api.ProtocolDetector
接口,以Dubbo协议为例,规则是检测前2个字节是否是0xdabb
。
java
public class DubboDetector implements ProtocolDetector {
private final ChannelBuffer Preface = new ByteBufferBackedChannelBuffer(
ByteBuffer.wrap(new byte[]{(byte)0xda, (byte)0xbb})
);
@Override
public Result detect(ChannelBuffer in) {
int prefaceLen = Preface.readableBytes();
int bytesRead = min(in.readableBytes(), prefaceLen);
if (bytesRead ==0 || !ChannelBuffers.prefixEquals(in, Preface, bytesRead)) {
return Result.UNRECOGNIZED;
}
if (bytesRead == prefaceLen) {
return Result.RECOGNIZED;
}
return Result.NEED_MORE_DATA;
}
}
Dubbo3主推的Triple协议和grpc协议都是基于HTTP2的,所以如何检测客户端使用的是HTTP2协议呢?HTTP2规定了,客户端建立连接后,首先要发送一个魔法字符串,用于确认服务端支持HTTP2,这个魔法字符串内容是PRI * HTTP/2.0\r\n\r\nSM\r\n\r\n
。
java
public class Http2ProtocolDetector implements ProtocolDetector {
private final ChannelBuffer clientPrefaceString = new ByteBufferBackedChannelBuffer(
Http2CodecUtil.connectionPrefaceBuf().nioBuffer());
@Override
public Result detect(ChannelBuffer in) {
int prefaceLen = clientPrefaceString.readableBytes();
int bytesRead = min(in.readableBytes(), prefaceLen);
// If the input so far doesn't match the preface, break the connection.
if (bytesRead == 0 || !ChannelBuffers.prefixEquals(in, clientPrefaceString, bytesRead)) {
return Result.UNRECOGNIZED;
}
if (bytesRead == prefaceLen) {
return Result.RECOGNIZED;
}
return Result.NEED_MORE_DATA;
}
}
Http2CodecUtil.connectionPrefaceBuf()
内容就是魔法字符串。
java
private static final ByteBuf CONNECTION_PREFACE =
unreleasableBuffer(directBuffer(24)
.writeBytes("PRI * HTTP/2.0\r\n\r\nSM\r\n\r\n".getBytes(UTF_8)))
asReadOnly();
配置Handler
协议一旦检测确认,协议检测的Handler对于子Channel来说就没用了,会从ChannelPipeline中移除。
协议确认后,会通过WireProtocol#configServerProtocolHandler()
来配置ChannelPipeline。
因此已经知道客户端使用哪种协议调用服务了,所以就可以针对性的配置编解码器、业务处理等Handler了。
以HTTP2为例,核心是需要配置Http2FrameCodec
对HTTP2 Frame编解码、配置Http2MultiplexHandler
以支持多路复用。
java
public void configServerProtocolHandler(URL url, ChannelOperator operator) {
Configuration config = ConfigurationUtils.getGlobalConfiguration(url.getOrDefaultApplicationModel());
final List<HeaderFilter> headFilters;
if (filtersLoader != null) {
headFilters = filtersLoader.getActivateExtension(url, HEADER_FILTER_KEY);
} else {
headFilters = Collections.emptyList();
}
final Http2FrameCodec codec = Http2FrameCodecBuilder.forServer()
.gracefulShutdownTimeoutMillis(10000)
.initialSettings(new Http2Settings().headerTableSize(
config.getInt(H2_SETTINGS_HEADER_TABLE_SIZE_KEY, DEFAULT_SETTING_HEADER_LIST_SIZE))
.maxConcurrentStreams(
config.getInt(H2_SETTINGS_MAX_CONCURRENT_STREAMS_KEY, Integer.MAX_VALUE))
.initialWindowSize(
config.getInt(H2_SETTINGS_INITIAL_WINDOW_SIZE_KEY, DEFAULT_WINDOW_INIT_SIZE))
.maxFrameSize(config.getInt(H2_SETTINGS_MAX_FRAME_SIZE_KEY, DEFAULT_MAX_FRAME_SIZE))
.maxHeaderListSize(config.getInt(H2_SETTINGS_MAX_HEADER_LIST_SIZE_KEY,
DEFAULT_MAX_HEADER_LIST_SIZE)))
.frameLogger(SERVER_LOGGER)
.build();
final Http2MultiplexHandler handler = new Http2MultiplexHandler(
new ChannelInitializer<Channel>() {
@Override
protected void initChannel(Channel ch) {
final ChannelPipeline p = ch.pipeline();
p.addLast(new TripleCommandOutBoundHandler());
p.addLast(new TripleHttp2FrameServerHandler(frameworkModel, lookupExecutor(url),
headFilters));
}
});
List<ChannelHandler> handlers = new ArrayList<>();
handlers.add(new ChannelHandlerPretender(codec));// Http2 Frame 编解码器
handlers.add(new ChannelHandlerPretender(new TripleServerConnectionHandler()));// 处理 PING GOAWAY
handlers.add(new ChannelHandlerPretender(handler));// 请求处理器
handlers.add(new ChannelHandlerPretender(new TripleTailHandler()));// 避免内存泄漏
operator.configChannelHandler(handlers);
}