简易RPC框架-私有协议栈

*:first-child {
margin-top: 0 !important; }
body > *:last-child {
margin-bottom: 0 !important; }

a {
color: #4183C4; }
a.absent {
color: #cc0000; }
a.anchor {
display: block;
padding-left: 30px;
margin-left: -30px;
cursor: pointer;
position: absolute;
top: 0;
left: 0;
bottom: 0; }

h1, h2, h3, h4, h5, h6 {
margin: 20px 0 10px;
padding: 0;
font-weight: bold;
-webkit-font-smoothing: antialiased;
cursor: text;
position: relative; }

h1:hover a.anchor, h2:hover a.anchor, h3:hover a.anchor, h4:hover a.anchor, h5:hover a.anchor, h6:hover a.anchor {
background: url(data:image/png;base64,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) no-repeat 10px center;
text-decoration: none; }

h1 tt, h1 code {
font-size: inherit; }

h2 tt, h2 code {
font-size: inherit; }

h3 tt, h3 code {
font-size: inherit; }

h4 tt, h4 code {
font-size: inherit; }

h5 tt, h5 code {
font-size: inherit; }

h6 tt, h6 code {
font-size: inherit; }

h1 {
font-size: 28px;
color: black; }

h2 {
font-size: 24px;
border-bottom: 1px solid #cccccc;
color: black; }

h3 {
font-size: 18px; }

h4 {
font-size: 16px; }

h5 {
font-size: 14px; }

h6 {
color: #777777;
font-size: 14px; }

p, blockquote, ul, ol, dl, li, table, pre {
margin: 15px 0; }

hr {
background: transparent url(data:image/png;base64,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) repeat-x 0 0;
border: 0 none;
color: #cccccc;
height: 4px;
padding: 0;
}

body > h2:first-child {
margin-top: 0;
padding-top: 0; }
body > h1:first-child {
margin-top: 0;
padding-top: 0; }
body > h1:first-child + h2 {
margin-top: 0;
padding-top: 0; }
body > h3:first-child, body > h4:first-child, body > h5:first-child, body > h6:first-child {
margin-top: 0;
padding-top: 0; }

a:first-child h1, a:first-child h2, a:first-child h3, a:first-child h4, a:first-child h5, a:first-child h6 {
margin-top: 0;
padding-top: 0; }

h1 p, h2 p, h3 p, h4 p, h5 p, h6 p {
margin-top: 0; }

li p.first {
display: inline-block; }
li {
margin: 0; }
ul, ol {
padding-left: 30px; }

ul :first-child, ol :first-child {
margin-top: 0; }

dl {
padding: 0; }
dl dt {
font-size: 14px;
font-weight: bold;
font-style: italic;
padding: 0;
margin: 15px 0 5px; }
dl dt:first-child {
padding: 0; }
dl dt > :first-child {
margin-top: 0; }
dl dt > :last-child {
margin-bottom: 0; }
dl dd {
margin: 0 0 15px;
padding: 0 15px; }
dl dd > :first-child {
margin-top: 0; }
dl dd > :last-child {
margin-bottom: 0; }

blockquote {
border-left: 4px solid #dddddd;
padding: 0 15px;
color: #777777; }
blockquote > :first-child {
margin-top: 0; }
blockquote > :last-child {
margin-bottom: 0; }

img {
max-width: 100%; }

span.frame {
display: block;
overflow: hidden; }
span.frame > span {
border: 1px solid #dddddd;
display: block;
float: left;
overflow: hidden;
margin: 13px 0 0;
padding: 7px;
width: auto; }
span.frame span img {
display: block;
float: left; }
span.frame span span {
clear: both;
color: #333333;
display: block;
padding: 5px 0 0; }
span.align-center {
display: block;
overflow: hidden;
clear: both; }
span.align-center > span {
display: block;
overflow: hidden;
margin: 13px auto 0;
text-align: center; }
span.align-center span img {
margin: 0 auto;
text-align: center; }
span.align-right {
display: block;
overflow: hidden;
clear: both; }
span.align-right > span {
display: block;
overflow: hidden;
margin: 13px 0 0;
text-align: right; }
span.align-right span img {
margin: 0;
text-align: right; }
span.float-left {
display: block;
margin-right: 13px;
overflow: hidden;
float: left; }
span.float-left span {
margin: 13px 0 0; }
span.float-right {
display: block;
margin-left: 13px;
overflow: hidden;
float: right; }
span.float-right > span {
display: block;
overflow: hidden;
margin: 13px auto 0;
text-align: right; }

code, tt {
margin: 0 2px;
padding: 0 5px;
white-space: nowrap;
border: 1px solid #eaeaea;
background-color: #f8f8f8;
border-radius: 3px; }

pre code {
margin: 0;
padding: 0;
white-space: pre;
border: none;
background: transparent; }

.highlight pre {
background-color: #f8f8f8;
border: 1px solid #cccccc;
font-size: 13px;
line-height: 19px;
overflow: auto;
padding: 6px 10px;
border-radius: 3px; }

pre {
background-color: #f8f8f8;
border: 1px solid #cccccc;
font-size: 13px;
line-height: 19px;
overflow: auto;
padding: 6px 10px;
border-radius: 3px; }
pre code, pre tt {
background-color: transparent;
border: none; }

sup {
font-size: 0.83em;
vertical-align: super;
line-height: 0;
}

kbd {
display: inline-block;
padding: 3px 5px;
font-size: 11px;
line-height: 10px;
color: #555;
vertical-align: middle;
background-color: #fcfcfc;
border: solid 1px #ccc;
border-bottom-color: #bbb;
border-radius: 3px;
box-shadow: inset 0 -1px 0 #bbb
}

* {
-webkit-print-color-adjust: exact;
}
@media screen and (min-width: 914px) {

}
@media print {
table, pre {
page-break-inside: avoid;
}
pre {
word-wrap: break-word;
}
}
-->
code[class*="language-"],
pre[class*="language-"] {
background: #f5f2f0;
}

/* Inline code */
:not(pre) > code[class*="language-"] {
padding: .1em;
border-radius: .3em;
white-space: normal;
}

.token.comment,
.token.prolog,
.token.doctype,
.token.cdata {
color: slategray;
}

.token.punctuation {
color: #999;
}

.namespace {
opacity: .7;
}

.token.property,
.token.tag,
.token.boolean,
.token.number,
.token.constant,
.token.symbol,
.token.deleted {
color: #905;
}

.token.selector,
.token.attr-name,
.token.string,
.token.char,
.token.builtin,
.token.inserted {
color: #690;
}

.token.operator,
.token.entity,
.token.url,
.language-css .token.string,
.style .token.string {
color: #a67f59;
background: hsla(0, 0%, 100%, .5);
}

.token.atrule,
.token.attr-value,
.token.keyword {
color: #07a;
}

.token.function {
color: #DD4A68;
}

.token.regex,
.token.important,
.token.variable {
color: #e90;
}

.token.important,
.token.bold {
font-weight: bold;
}
.token.italic {
font-style: italic;
}

.token.entity {
cursor: help;
}
-->

HTTP协议

客户机与服务端之间的数据交互需要遵守一定的约定，比如协议版本，数据类型，是否有缓存，是否有压缩等，只有在这些约定的基础上才能相互之间愉快的工作。

Netty通信过程中的编解码

这时说的是基于TCP/IP的Netty之间的通信。TCP/IP协议下客户端与服务端之间要进行数据交互，一般需要将数据转换成二进制格式，直接传java bean是不能支持的。在RPC模式下客户端在向服务端发起请求前需要将数据做编码，服务端在接收客户端发的数据后需要做解码之后才能正常工作。

• 解码流程

• 编码流程

Netty 私有协议栈

为了更好的控制RPC客户端与服务端之间的通信，也可以编写私有的协议栈来支撑。

定义消息体

类似HTTP协议，包含头信息以及内容信息。

public class RpcMessage implements Serializable {

    private RpcMessageHeader messageHeader;

    private Object messageBody;

}

头信息，包含内容体长度，消息类型等信息。可以根据消息类型来做不同的业务，比如区分是心跳信息还是业务或者是监控之类的信息。

public class RpcMessageHeader implements Serializable {
    private int length;

    private int type;

}

定义解码器

因为TCP/IP协议容易出现粘包拆包现象，这里为了简单直接选择继承组件提供的LengthFieldBasedFrameDecoder，只需要重写下面的方法即可：

 public Object decode(ChannelHandlerContext ctx, ByteBuf in) throws Exception {
        ByteBuf frame=(ByteBuf)super.decode(ctx,in);
        if(null==frame){
            return null;
        }

        RpcMessage message=new RpcMessage();
        RpcMessageHeader messageHeader=new RpcMessageHeader();
        messageHeader.setLength(frame.readInt());
        message.setMessageHeader(messageHeader);

        byte[] data = new byte[message.getMessageHeader().getLength()];
        frame.readBytes(data);

        Object obj = ProtoStuffSerializeUtil.deserialize(data, genericClass);
        message.setMessageBody(obj);
        return message;
    }

定义编码器

编码器继承MessageToByteEncoder，将对象转换成字节的编码器

public class RpcEncoder extends MessageToByteEncoder<RpcMessage>

重点是下面的编码函数，在ByteBuf中输出数据长度以及数据体，如有其它需要可以补充其它的字段，比如消息类型。

 public void encode(ChannelHandlerContext ctx, RpcMessage in, ByteBuf out) throws Exception {
        if(null==in){
            throw new RpcException("RpcMessage is null");
        }
        if (genericClass.isInstance(in.getMessageBody())) {
            byte[] data = ProtoStuffSerializeUtil.serialize(in.getMessageBody());
            out.writeInt(data.length);
            out.writeBytes(data);
        }
    }

ServerHandle

• 修改服务端执行器消息实体类型为新定义的RpcMessage

public class RpcServerInvoker extends AbstractInvoker<RpcMessage>

• 修改服务端回调

从服务端方法获取到返回的结果后，重新封装成消息对象（RpcMessage）发送给客户端。

protected void channelRead0(ChannelHandlerContext channelHandlerContext, RpcMessage message) {

        this.executor.execute(new Runnable() {
            @Override
            public void run() {
                RpcInvoker rpcInvoker=RpcServerInvoker.this.buildInvokerChain(RpcServerInvoker.this);
                RpcResponse response=(RpcResponse) rpcInvoker.invoke(RpcServerInvoker.this.buildRpcInvocation((RpcRequest) message.getMessageBody()));
                RpcMessage responseMessage=new RpcMessage();
                byte[] data = ProtoStuffSerializeUtil.serialize(response);
                RpcMessageHeader messageHeader=new RpcMessageHeader();
                messageHeader.setLength(data.length);
                responseMessage.setMessageHeader(messageHeader);
                responseMessage.setMessageBody(response);
                channelHandlerContext.writeAndFlush(responseMessage);
            }
        });

    }

ClientHandle

• 修改客户端执行器消息实体类型为新定义的RpcMessage

public class RpcClientInvoker extends AbstractInvoker<RpcMessage>

• 修改客户端回调方法

接收的返回结果修改为RpcMessage，从body属性中获取原来的RpcResponse对象

public void channelRead0(ChannelHandlerContext ctx, RpcMessage message) {
        RpcResponse response=(RpcResponse) message.getMessageBody();
        String requestId = response.getRequestId();
        ResponseFuture responseFuture = pendingRPC.get(requestId);
        if (responseFuture != null) {
            pendingRPC.remove(requestId);
            responseFuture.done(response);
        }
    }

• 修改发送请求的消息对象，组装成RpcMessage发送

public ResponseFuture invoke(RpcInvocation invocation) {
        RpcRequest request=this.getRpcRequest();
        ResponseFuture responseFuture = new ResponseFuture(request);
        pendingRPC.put(request.getRequestId(), responseFuture);
        RpcMessage message=new RpcMessage();
        byte[] data = ProtoStuffSerializeUtil.serialize(request);
        RpcMessageHeader messageHeader=new RpcMessageHeader();
        messageHeader.setLength(data.length);
        message.setMessageHeader(messageHeader);
        message.setMessageBody(request);
        channel.writeAndFlush(message);
        return responseFuture;
    }

本文源码

https://github.com/jiangmin168168/jim-framework

文中代码是依赖上述项目的，如果有不明白的可下载源码

引用

• 文中插图来自来网络
• 文中的思路参考了Netty权威指南