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<title>Spring Cloud Gateway有状态路由</title>
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<h1>Spring Cloud Gateway有状态路由</h1>
<div class="details">
<span id="author" class="author">pxzxj</span><br>
<span id="author2" class="author">pudge.zxj@gmail.com</span><br>
<span id="author3" class="author">2023/03/08</span><br>
</div>
<div id="toc" class="toc2">
<div id="toctitle">Table of Contents</div>
<span id="back-to-index"><a href="index.html">Back to index</a></span><ul class="sectlevel1">
<li><a href="#_项目准备">1. 项目准备</a></li>
<li><a href="#_配置验证">2. 配置验证</a></li>
</ul>
</div>
</div>
<div id="content">
<div id="preamble">
<div class="sectionbody">
<div class="paragraph">
<p>Spring Cloud Gateway是目前最流行的网关实现之一，通常与Spring Cloud中其它框架一起用于构建微服务项目，Spring Cloud Gateway默认是按照负载均衡的方式将请求路由到后端服务实例的，但在某些特殊场景下则需要有状态路由，例如服务有两个接口其中一个用于生成文件存储在本地，下一个接口用于下载生成的文件。本文介绍有状态路由的实现方法</p>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_项目准备"><a class="anchor" href="#_项目准备"></a>1. 项目准备</h2>
<div class="sectionbody">
<div class="paragraph">
<p>新建一个网关项目 <code>gateway</code> 和后端服务项目 <code>backend</code>，并在 <code>backend</code> 中定义两个有状态的接口</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="highlight"><code class="language-java" data-lang="java">@RestController
public class MyController {

    private final Map&lt;String, String&gt; map = new HashMap&lt;&gt;();

    @RequestMapping("/get")
    public String get() {
        return map.get("key");
    }

    @RequestMapping("/set/{value}")
    public void set(@PathVariable String value) {
        map.put("key", value);
    }
}
</code></pre>
</div>
</div>
<div class="paragraph">
<p><code>backend</code> 启动两个实例并在 <code>gateway</code> 中配置两个实例的地址，此处为 <code>localhost:8082</code> 和 <code>localhost:8083</code>，对应的实例Id是 <code>ins2</code> 和 <code>ins3</code></p>
</div>
<div class="listingblock">
<div class="content">
<pre class="highlight"><code class="language-yaml" data-lang="yaml">server:
  port: 8081
spring:
  cloud:
    discovery:
      client:
        simple:
          instances:
            backend:
              - uri: http://localhost:8082
                instance-id: ins2
              - uri: http://localhost:8083
                instance-id: ins3
    gateway:
      routes:
        - id: backend
          uri: lb://backend
          predicates:
            - Path=/**</code></pre>
</div>
</div>
<div class="admonitionblock tip">
<table>
<tr>
<td class="icon">
<i class="fa icon-tip" title="Tip"></i>
</td>
<td class="content">
完整项目源码参考 <a href="https://github.com/pxzxj/spring-cloud-gateway-stateful-route">GitHub</a>
</td>
</tr>
</table>
</div>
<div class="paragraph">
<p>此时通过网关先调用 <code>/set/vv</code> 接口再调用 <code>/get</code> 接口是显然无法获取到上一步保存的 <code>vv</code> 的，因为按照默认的负载均衡算法，两次请求被路由到了不同的 <code>backend</code> 实例上</p>
</div>
<div class="listingblock">
<div class="content">
<pre>C:\Users\pxzxj1&gt;curl "http://localhost:8081/set/vv"

C:\Users\pxzxj1&gt;curl "http://localhost:8081/get"

C:\Users\pxzxj1&gt;</pre>
</div>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_配置验证"><a class="anchor" href="#_配置验证"></a>2. 配置验证</h2>
<div class="sectionbody">
<div class="paragraph">
<p>Spring Cloud LoadBalancer提供了 <a href="https://docs.spring.io/spring-cloud-commons/docs/3.1.6/reference/html/#request-based-sticky-session-for-loadbalancer">Request-based Sticky Session</a>配置可以解决有状态路由问题，Spring Cloud Cloud也使用了Spring Cloud LoadBalancer实现路由选择</p>
</div>
<div class="paragraph">
<p>首先在网关的配置文件中添加如下内容</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="highlight"><code class="language-yaml" data-lang="yaml">spring:
  cloud:
    loadbalancer:
      configurations: request-based-sticky-session               <i class="conum" data-value="1"></i><b>(1)</b>
      sticky-session:
        add-service-instance-cookie: true                        <i class="conum" data-value="2"></i><b>(2)</b></code></pre>
</div>
</div>
<div class="olist arabic">
<ol class="arabic">
<li>
<p>基于请求中的Cookie路由，默认Cookie名称是 <code>sc-lb-instance-id</code></p>
</li>
<li>
<p>请求转发到后端时将选中的后端实例信息添加到请求的Cookie中</p>
</li>
</ol>
</div>
<div class="paragraph">
<p>为了将此次选中的实例信息返回客户端，后端接口也需要修改，将网关添加到请求中的Cookie添加到响应中</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="highlight"><code class="language-java" data-lang="java">@RestController
public class MyController {

    private final Map&lt;String, String&gt; map = new HashMap&lt;&gt;();

    @RequestMapping("/get")
    public String get() {
        return map.get("key");
    }

    @RequestMapping("/set/{value}")
    public void set(@PathVariable String value, HttpServletRequest request, HttpServletResponse response) {
        Cookie[] cookies = request.getCookies();
        if(cookies != null) {
            for(Cookie cookie : cookies) {
                if("sc-lb-instance-id".equals(cookie.getName())) {
                    response.addCookie(cookie);
                    break;
                }
            }
        }
        map.put("key", value);
    }
}
</code></pre>
</div>
</div>
<div class="paragraph">
<p>此时再次调用 <code>/set/vv</code> 接口可以在它的响应的Cookie中看到本次网关选中的后端实例为 <code>ins2</code>，那么调用 <code>/get</code> 时也附带上此Cookie就可以使网关把请求也路由到 <code>ins2</code>，从而获取到 <code>vv</code></p>
</div>
<div class="listingblock">
<div class="content">
<pre>C:\Users\pxzxj1&gt;curl "http://localhost:8081/set/vv" -v
*   Trying 127.0.0.1:8081...
* Connected to localhost (127.0.0.1) port 8081 (#0)
&gt; GET /set/vv HTTP/1.1
&gt; Host: localhost:8081
&gt; User-Agent: curl/7.83.1
&gt; Accept: */*
&gt;
* Mark bundle as not supporting multiuse
&lt; HTTP/1.1 200 OK
&lt; Set-Cookie: sc-lb-instance-id=ins2
&lt; Content-Length: 0
&lt; Date: Wed, 08 Mar 2023 08:44:57 GMT
&lt;
* Connection #0 to host localhost left intact

C:\Users\pxzxj1&gt;curl -H "Cookie: sc-lb-instance-id=ins2" "http://localhost:8081/get"
vv
C:\Users\pxzxj1&gt;</pre>
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Last updated 2024-03-18 05:44:42 UTC
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