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<h1 class="page__title" itemprop="headline">常见问题
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<section class="page__content" itemprop="text">
<ul>
<li>
<p><strong>Q: ServiceComb和SpringCloud是什么关系，具体的应用场景是什么？</strong></p>
<p>A: ServiceComb是华为基于内部多个大型IT系统实践提炼出来的一套微服务开发框架，在开发态基于最佳实践封装了一套微服务运行模型，这些能力对用户完全透明，可以通过配置引入功能和对其进行调整。在运维阶段充分考虑了微服务运维，提供了丰富的监控指标和动态治理能力。 <br />
B: ServiceComb的这套能力可以作为一个单独的开发框架，在需要轻量级微服务解决方案的的场景中单独使用，也可以建立在SpringCloud上，与SpringCloud提供的其他组件一起工作，在重量级场景中和SpringCloud一起产生 “1+1大于2”的效果。</p>
</li>
<li>
<p><strong>Q: 用IntelliJ的免费版开发，有什么问题？</strong></p>
<p>A: 没有问题，使用IntelliJ 开发，可参考 <a href="/cn/developers/setup-develop-environment/">Setup Developer Environment</a> 进行相应的环境配置。</p>
</li>
<li>
<p><strong>Q: 使用Java-Chassis这个框架时有什么需要注意的地方？</strong></p>
<p>A: 使用Java-Chassis有以下这些限制：
(1) 0.3.0-SNAPSHOT之前的版本不支持类似<code class="language-plaintext highlighter-rouge">@GetMapping</code>这样的标注。
(2) 所用到的HTTP请求方法一样时，如GET，则方法名不能重载。这是由于生成契约时方法名会作为其Operation ID，所以要保证其唯一性。
(3) 方法和类必须是public的。</p>
</li>
<li>
<p><strong>Q: 契约生成会报错Caused by: java.lang.Error: OperationId must be unique，不支持函数重载？</strong></p>
<p>A: 我们是支持函数重载的， 加上<code class="language-plaintext highlighter-rouge">@ApiOperation</code>标签即可，demo-pojo中有示例。每个接口必须有唯一的operation id。</p>
</li>
<li>
<p><strong>Q: 使用<em>spring-boot-starter-provider</em>这个依赖时，在<em>application.yml</em>文件中声明的<code class="language-plaintext highlighter-rouge">spring.main.web-application</code>属性并没有生效？</strong></p>
<p>A: 使用<em>starter-provider</em>这个依赖时，如果用到了servlet这种方式时，需要在<em>application.properties</em>这个文件引入<code class="language-plaintext highlighter-rouge">spring.main.web-application=true</code>这样的属性或者在<em>application.yml</em>文件中声明，但是此时需要新建一个<em>application.properties</em>的文件，其内容可以为空。</p>
</li>
<li>
<p><strong>Q: 网关依赖的jar和其他微服务的一样吗？</strong></p>
<div class="language-xml highlighter-rouge"><div class="highlight"><pre class="highlight"><code> <span class="nt">&lt;groupId&gt;</span>org.apache.servicecomb<span class="nt">&lt;/groupId&gt;</span>
<span class="nt">&lt;artifactId&gt;</span>spring-boot-starter-provider<span class="nt">&lt;/artifactId&gt;</span>
</code></pre></div> </div>
<p>A: 网关除了要依赖<code class="language-plaintext highlighter-rouge">spring-boot-starter-provider</code>之外还要依赖<code class="language-plaintext highlighter-rouge">spring-boot-starter-discovery</code>，可以参考<a href="https://github.com/ServiceComb/LinuxCon-Beijing-WorkShop">LinuxCon-Beijing-Workshop</a>中manager的实现。</p>
</li>
<li>
<p><strong>Q: 网关需要像其他微服务一样配置assembly吗？其中的/maven/gateway这个路径是docker maven plugin默认的吗？</strong></p>
<p>A: 需要，由于项目现在使用的是spring-boot的打包方式，docker maven plugin也是依赖打包生成的文件来生成docker镜像的。/maven这个路径是docker maven plugin指定的，而gateway这个路径是在assembly中指定的。</p>
</li>
<li>
<p><strong>Q: 服务接口的返回类型可以是任意类型吗？还是必须是responseEntity？</strong></p>
<p>A: 可以，具体可以参考java-chassis的<a href="https://github.com/apache/servicecomb-java-chassis/blob/master/integration-tests/springmvc-tests/src/test/java/org/apache/servicecomb/demo/springmvc/tests/SpringMvcIntegrationTestBase.java">integration-test的实现</a>。</p>
</li>
<li>
<p><strong>Q: 微服务启动后，无法正确调用接口，或返回不存在错误？</strong></p>
<p>A: 请检查调用路径与Producer实现代码中发布的路径完全一致。Producer端的启动日志可以查看到映射路径输出，例如：</p>
<p><code class="language-plaintext highlighter-rouge">[INFO] Swagger mapped "{[/hello/], method=[GET], produces=[application/json]}"</code></p>
<p>不同编程风格（模型）实现Producer的文档和注意事项请参见：<a href="/cn/users/develop-with-jax-rs/">Jaxrs</a> <a href="/cn/users/develop-with-springmvc/">SpringMVC</a> <a href="/cn/users/develop-with-transparent-rpc/">Pojo</a> <a href="/cn/users/develop-with-spring-boot-starter/">Spring Boot</a> 。</p>
</li>
<li>
<p><strong>Q: 在eclipse下修改了microservice.yaml配置文件下的端口号，启动程序后，端口号没生效？</strong></p>
<p>A: 需要单独导入sample项目，如果导入整个ServiceComb-Java-Chassis项目，由于sample目录不在ServiceComb-Java-Chassis模块中，IDE不会对sample进行编译,eclipse下并没有提示错误信息，IDEA下会有提示信息。因此eclipse启动sample的demo会发现修改了端口没有生效。</p>
</li>
<li>
<p><strong>Q: 如何自定义某个Java方法对应的REST接口里的HTTP Status Code？</strong></p>
<p>A: 对于正常的返回值，可以通过SwaggerAnnotation实现，例如：</p>
<div class="language-java highlighter-rouge"><div class="highlight"><pre class="highlight"><code> <span class="nd">@ApiResponse</span><span class="o">(</span><span class="n">code</span> <span class="o">=</span> <span class="mi">300</span><span class="o">,</span> <span class="n">response</span> <span class="o">=</span> <span class="nc">String</span><span class="o">.</span><span class="na">class</span><span class="o">,</span> <span class="n">message</span> <span class="o">=</span> <span class="s">""</span><span class="o">)</span>
<span class="kd">public</span> <span class="kt">int</span> <span class="nf">test</span><span class="o">(</span><span class="kt">int</span> <span class="n">x</span><span class="o">)</span> <span class="o">{</span>
<span class="k">return</span> <span class="mi">100</span><span class="o">;</span>
<span class="o">}</span>
</code></pre></div> </div>
<p>对于异常的返回值，可以通过抛出自定义的InvocationException实现，例如：、</p>
<div class="language-java highlighter-rouge"><div class="highlight"><pre class="highlight"><code> <span class="kd">public</span> <span class="nc">String</span> <span class="nf">testException</span><span class="o">(</span><span class="kt">int</span> <span class="n">code</span><span class="o">)</span> <span class="o">{</span>
<span class="nc">String</span> <span class="n">strCode</span> <span class="o">=</span> <span class="nc">String</span><span class="o">.</span><span class="na">valueOf</span><span class="o">(</span><span class="n">code</span><span class="o">);</span>
<span class="k">switch</span> <span class="o">(</span><span class="n">code</span><span class="o">)</span> <span class="o">{</span>
<span class="k">case</span> <span class="mi">200</span><span class="o">:</span>
<span class="k">return</span> <span class="n">strCode</span><span class="o">;</span>
<span class="k">case</span> <span class="mi">456</span><span class="o">:</span>
<span class="k">throw</span> <span class="k">new</span> <span class="nf">InvocationException</span><span class="o">(</span><span class="n">code</span><span class="o">,</span> <span class="n">strCode</span><span class="o">,</span> <span class="n">strCode</span> <span class="o">+</span> <span class="s">" error"</span><span class="o">);</span>
<span class="k">case</span> <span class="mi">556</span><span class="o">:</span>
<span class="k">throw</span> <span class="k">new</span> <span class="nf">InvocationException</span><span class="o">(</span><span class="n">code</span><span class="o">,</span> <span class="n">strCode</span><span class="o">,</span> <span class="nc">Arrays</span><span class="o">.</span><span class="na">asList</span><span class="o">(</span><span class="n">strCode</span> <span class="o">+</span> <span class="s">" error"</span><span class="o">));</span>
<span class="k">case</span> <span class="mi">557</span><span class="o">:</span>
<span class="k">throw</span> <span class="k">new</span> <span class="nf">InvocationException</span><span class="o">(</span><span class="n">code</span><span class="o">,</span> <span class="n">strCode</span><span class="o">,</span> <span class="nc">Arrays</span><span class="o">.</span><span class="na">asList</span><span class="o">(</span><span class="nc">Arrays</span><span class="o">.</span><span class="na">asList</span><span class="o">(</span><span class="n">strCode</span> <span class="o">+</span> <span class="s">" error"</span><span class="o">)));</span>
<span class="k">default</span><span class="o">:</span>
<span class="k">break</span><span class="o">;</span>
<span class="o">}</span>
<span class="k">return</span> <span class="s">"not expected"</span><span class="o">;</span>
<span class="o">}</span>
</code></pre></div> </div>
</li>
<li>
<p><strong>Q: 如何定制自己微服务的日志配置?</strong></p>
<p>A: ServiceComb不绑定日志器，只是使用了slf4j，用户可以自由选择log4j/log4j2/logback等等。ServiceComb提供了一个log4j的扩展，在标准log4j的基础上，支持log4j的properties文件的增量配置。</p>
<ul>
<li>默认以规则：”classpath*:config/log4j.properties”加载配置文件</li>
<li>实际会搜索出classpath中所有的<code class="language-plaintext highlighter-rouge">config/log4j.properties和config/log4j.*.properties</code>, 从搜索出的文件中切出<code class="language-plaintext highlighter-rouge">\*</code>的部分，进行alpha排序，然后按顺序加载，最后合成的文件作为log4j的配置文件。</li>
<li>如果要使用ServiceComb的log4j扩展，则需要调用Log4jUtils.init，否则完全按标准的日志器的规则使用。</li>
</ul>
</li>
<li>
<p><strong>Q: 当服务配置了多个transport的时候，在运行时是怎么选择使用哪个transport的？</strong></p>
<p>A:</p>
<ul>
<li>
<p>ServiceComb的consumer、transport、handler、producer之间是解耦的，各功能之间通过契约定义联合在一起工作的，即：
consumer使用透明rpc，还是springmvc开发与使用highway，还是RESTful在网络上传输没有关系与producer是使用透明rpc，还是jaxrs，或者是springmvc开发，也没有关系handler也不感知，业务开发方式以及传输方式</p>
</li>
<li>
<p>consumer访问producer，在运行时的transport选择上，总规则为：
consumer的transport与producer的endpoint取交集，如果交集后，还有多个transport可选择，则轮流使用</p>
<p>分解开来，存在以下场景：</p>
</li>
<li>当一个微服务producer同时开放了highway以及RESTful的endpoint
<ul>
<li>consumer进程中只部署了highway transport jar，则只会访问producer的highway endpoint</li>
<li>consumer进程中只部署了RESTful transport jar，则只会访问producer的RESTful endpoint</li>
<li>consumer进程中，同时部署了highway和RESTful transport jar，则会轮流访问producer的highway、RESTful endpoint</li>
</ul>
<p>如果，此时consumer想固定使用某个transport访问producer，可以在consumer进程的microservice.yaml中配置，指定transport的名称:</p>
<div class="language-yaml highlighter-rouge"><div class="highlight"><pre class="highlight"><code> <span class="na">servicecomb</span><span class="pi">:</span>
<span class="na">references</span><span class="pi">:</span>
<span class="s">&lt;service_name&gt;</span><span class="pi">:</span>
<span class="na">transport</span><span class="pi">:</span> <span class="s">highway</span>
</code></pre></div> </div>
</li>
<li>当一个微服务producer只开放了highway的endpoint
<ul>
<li>consumer进程只部署了highway transport jar，则正常使用highway访问</li>
<li>consumer进程只部署了RESTful transport jar，则无法访问</li>
<li>consumer进程同时部署了highway和RESTful transport jar，则正常使用highway访问</li>
</ul>
</li>
<li>当一个微服务producer只开放了RESTful的endpoint
<ul>
<li>consumer进程只部署了highway transport jar，则无法访问</li>
<li>consumer进程只部署了RESTful transport jar，则正常使用RESTful访问</li>
<li>consumer进程同时部署了highway和RESTful transport jar，则正常使用RESTful访问</li>
</ul>
</li>
</ul>
</li>
<li>
<p><strong>Q: swagger body参数类型定义错误，导致服务中心注册的内容没有类型信息</strong></p>
<p><strong>现象描述:</strong></p>
<p>定义如下接口，将参数放到body传递</p>
<div class="language-yaml highlighter-rouge"><div class="highlight"><pre class="highlight"><code> <span class="s">/testInherate</span><span class="pi">:</span>
<span class="na">post</span><span class="pi">:</span>
<span class="na">operationId</span><span class="pi">:</span> <span class="s2">"</span><span class="s">testInherate"</span>
<span class="na">parameters</span><span class="pi">:</span>
<span class="pi">-</span> <span class="na">in</span><span class="pi">:</span> <span class="s2">"</span><span class="s">body"</span>
<span class="na">name</span><span class="pi">:</span> <span class="s2">"</span><span class="s">xxxxx"</span>
<span class="na">required</span><span class="pi">:</span> <span class="no">false</span>
<span class="na">type</span><span class="pi">:</span> <span class="s">string</span>
<span class="na">responses</span><span class="pi">:</span>
<span class="na">200</span><span class="pi">:</span>
<span class="na">description</span><span class="pi">:</span> <span class="s2">"</span><span class="s">response</span><span class="nv"> </span><span class="s">of</span><span class="nv"> </span><span class="s">200"</span>
<span class="na">schema</span><span class="pi">:</span>
<span class="s">$ref</span><span class="pi">:</span> <span class="s2">"</span><span class="s">#/definitions/ResponseImpl"</span>
</code></pre></div> </div>
<p>采用上面方式定义接口。在服务注册以后，从服务中心查询下来的接口type: string 丢失，变成了：</p>
<div class="language-yaml highlighter-rouge"><div class="highlight"><pre class="highlight"><code> <span class="s">/testInherate</span><span class="pi">:</span>
<span class="na">post</span><span class="pi">:</span>
<span class="na">operationId</span><span class="pi">:</span> <span class="s2">"</span><span class="s">testInherate"</span>
<span class="na">parameters</span><span class="pi">:</span>
<span class="pi">-</span> <span class="na">in</span><span class="pi">:</span> <span class="s2">"</span><span class="s">body"</span>
<span class="na">name</span><span class="pi">:</span> <span class="s2">"</span><span class="s">xxxxx"</span>
<span class="na">required</span><span class="pi">:</span> <span class="no">false</span>
<span class="na">responses</span><span class="pi">:</span>
<span class="na">200</span><span class="pi">:</span>
<span class="na">description</span><span class="pi">:</span> <span class="s2">"</span><span class="s">response</span><span class="nv"> </span><span class="s">of</span><span class="nv"> </span><span class="s">200"</span>
<span class="na">schema</span><span class="pi">:</span>
<span class="s">$ref</span><span class="pi">:</span> <span class="s2">"</span><span class="s">#/definitions/ResponseImpl"</span>
</code></pre></div> </div>
<p>如果客户端没有放置swagger，还会报告如下异常：</p>
<div class="language-text highlighter-rouge"><div class="highlight"><pre class="highlight"><code> Caused by: java.lang.ClassFormatError: Method "testInherate" in class ? has illegal signature "
</code></pre></div> </div>
<p>A：定义body参数的类型的时候，需要使用schema，不能直接使用type。</p>
<div class="language-yaml highlighter-rouge"><div class="highlight"><pre class="highlight"><code> <span class="s">/testInherate</span><span class="pi">:</span>
<span class="na">post</span><span class="pi">:</span>
<span class="na">operationId</span><span class="pi">:</span> <span class="s2">"</span><span class="s">testInherate"</span>
<span class="na">parameters</span><span class="pi">:</span>
<span class="pi">-</span> <span class="na">in</span><span class="pi">:</span> <span class="s2">"</span><span class="s">body"</span>
<span class="na">name</span><span class="pi">:</span> <span class="s2">"</span><span class="s">request"</span>
<span class="na">required</span><span class="pi">:</span> <span class="no">false</span>
<span class="na">schema</span><span class="pi">:</span>
<span class="na">type</span><span class="pi">:</span> <span class="s">string</span>
<span class="na">responses</span><span class="pi">:</span>
<span class="na">200</span><span class="pi">:</span>
<span class="na">description</span><span class="pi">:</span> <span class="s2">"</span><span class="s">response</span><span class="nv"> </span><span class="s">of</span><span class="nv"> </span><span class="s">200"</span>
<span class="na">schema</span><span class="pi">:</span>
<span class="s">$ref</span><span class="pi">:</span> <span class="s2">"</span><span class="s">#/definitions/ResponseImpl"</span>
</code></pre></div> </div>
</li>
<li>
<p><strong>Q: ServiceComb微服务框架服务调用是否使用长连接?</strong></p>
<p>A: http使用的是长连接（有超时时间），highway方式使用的是长连接（一直保持）。</p>
</li>
<li>
<p><strong>Q: 服务断连服务中心注册信息是否自动删除</strong></p>
<p>A: 服务中心心跳检测到服务实例不可用，只会移除服务实例信息，服务的静态数据不会移除。</p>
</li>
<li>
<p><strong>Q: 如果使用tomcat方式集成ServiceComb微服务框架，如何实现服务注册</strong></p>
<p>A: 如果使用cse sdk servlet方式（使用transport-rest-servlet依赖）制作为war包部署到tomcat，需要保证，服务描述文件（microservice.yaml）中rest端口配置和外置容器一致才能实现该服务的正确注册。否则无法感知tomcat开放端口。</p>
</li>
<li>
<p><strong>Q: 如果使用tomcat方式集成CSE微服务框架，服务注册的时候如何将war包部署的上下文注册到服务中心</strong></p>
<p>A: 发布服务接口的时候需要将war包部署的上下文（context）放在baseurl最前面，这样才能保证注册到服务中心的路径是完整的路径（包含了上下文）。实例：</p>
<div class="language-java highlighter-rouge"><div class="highlight"><pre class="highlight"><code> <span class="nd">@path</span><span class="o">(/{</span><span class="n">context</span><span class="o">}/</span><span class="n">xxx</span><span class="o">)</span>
<span class="kd">class</span> <span class="nc">ServiceA</span>
</code></pre></div> </div>
</li>
<li>
<p><strong>Q: ServiceComb微服务框架如何实现数据多个微服务间透传</strong></p>
<p>A:
透传数据塞入：</p>
<div class="language-java highlighter-rouge"><div class="highlight"><pre class="highlight"><code> <span class="nc">CseHttpEntity</span><span class="o">&lt;</span><span class="n">xxxx</span><span class="o">.</span><span class="na">class</span><span class="o">&gt;</span> <span class="n">httpEntity</span> <span class="o">=</span> <span class="k">new</span> <span class="nc">CseHttpEntity</span><span class="o">&lt;&gt;(</span><span class="n">xxx</span><span class="o">);</span>
<span class="c1">//透传内容</span>
<span class="n">httpEntity</span><span class="o">.</span><span class="na">addContext</span><span class="o">(</span><span class="s">"contextKey"</span><span class="o">,</span><span class="s">"contextValue"</span><span class="o">);</span>
<span class="nc">ResponseEntity</span><span class="o">&lt;</span><span class="nc">String</span><span class="o">&gt;</span> <span class="n">responseEntity</span> <span class="o">=</span> <span class="nc">RestTemplateBuilder</span><span class="o">.</span><span class="na">create</span><span class="o">().</span><span class="na">exchange</span><span class="o">(</span><span class="s">"cse://springmvc/springmvchello/sayhello"</span><span class="o">,</span><span class="nc">HttpMethod</span><span class="o">.</span><span class="na">POST</span><span class="o">,</span><span class="n">httpEntity</span><span class="o">,</span><span class="nc">String</span><span class="o">.</span><span class="na">class</span><span class="o">);</span>
</code></pre></div> </div>
<p>透传数据获取：</p>
<div class="language-java highlighter-rouge"><div class="highlight"><pre class="highlight"><code> <span class="nd">@Override</span>
<span class="nd">@RequestMapping</span><span class="o">(</span><span class="n">path</span><span class="o">=</span><span class="s">"/sayhello"</span><span class="o">,</span><span class="n">method</span> <span class="o">=</span> <span class="nc">RequestMethod</span><span class="o">.</span><span class="na">POST</span><span class="o">)</span>
<span class="kd">public</span> <span class="nc">String</span> <span class="nf">sayHello</span><span class="o">(</span><span class="nd">@RequestBody</span> <span class="nc">Person</span> <span class="n">person</span><span class="o">,</span><span class="nc">InvocationContext</span> <span class="n">context</span><span class="o">){</span>
<span class="c1">//透传数据获取</span>
<span class="n">context</span><span class="o">.</span><span class="na">getContext</span><span class="o">();</span>
<span class="k">return</span> <span class="s">"Hello person "</span> <span class="o">+</span> <span class="n">person</span><span class="o">.</span><span class="na">getName</span><span class="o">();</span>
<span class="o">}</span>
</code></pre></div> </div>
</li>
<li>
<p><strong>Q: ServiceComb微服务框架服务如何自定义返回状态码?</strong></p>
<p>A:</p>
<div class="language-java highlighter-rouge"><div class="highlight"><pre class="highlight"><code> <span class="nd">@Override</span>
<span class="nd">@RequestMapping</span><span class="o">(</span><span class="n">path</span> <span class="o">=</span> <span class="s">"/sayhello"</span><span class="o">,</span><span class="n">method</span> <span class="o">=</span> <span class="nc">RequestMethod</span><span class="o">.</span><span class="na">POST</span><span class="o">)</span>
<span class="kd">public</span> <span class="nc">String</span> <span class="nf">sayHello</span><span class="o">(</span><span class="nd">@RequestBody</span> <span class="nc">Person</span> <span class="n">person</span><span class="o">){</span>
<span class="nc">InvocationContext</span> <span class="n">context</span> <span class="o">=</span> <span class="nc">ContextUtils</span><span class="o">.</span><span class="na">getInvocationContext</span><span class="o">();</span>
<span class="c1">//自定义状态码</span>
<span class="n">context</span><span class="o">.</span><span class="na">setStatus</span><span class="o">(</span><span class="nc">Status</span><span class="o">.</span><span class="na">CREATED</span><span class="o">);</span>
<span class="k">return</span> <span class="s">"Hello person "</span><span class="o">+</span><span class="n">person</span><span class="o">.</span><span class="na">getName</span><span class="o">();</span>
<span class="o">}</span>
</code></pre></div> </div>
</li>
<li>
<p><strong>Q: ServiceComb body Model部分暴露</strong></p>
<p>A: 一个接口对应的body对象中，可能有一些属性是内部的，不想开放出去，生成schema的时候不要带出去，使用：</p>
<div class="language-java highlighter-rouge"><div class="highlight"><pre class="highlight"><code> <span class="nd">@ApiModelProperty</span><span class="o">(</span><span class="n">hidden</span> <span class="o">=</span> <span class="kc">true</span><span class="o">)</span>
</code></pre></div> </div>
</li>
<li>
<p><strong>Q: ServiceComb框架获取远端consumer的地址</strong></p>
<p>A: 如果使用http rest方式（使用transport-rest-vertx依赖）可以用下面这种方式获取：</p>
<div class="language-java highlighter-rouge"><div class="highlight"><pre class="highlight"><code> <span class="nc">AbstractProducerContextArgMapper</span> <span class="n">httpRequestCreator</span> <span class="o">=</span> <span class="o">(</span><span class="nc">AbstractProducerContextArgMapper</span><span class="o">)</span><span class="n">invocation</span><span class="o">.</span><span class="na">getHandlerContext</span><span class="o">().</span><span class="na">get</span><span class="o">(</span><span class="nc">RestConst</span><span class="o">.</span><span class="na">HTTP_REQUEST_CREATOR</span><span class="o">);</span>
<span class="k">if</span><span class="o">(</span><span class="n">httpRequestCreator</span> <span class="o">!=</span> <span class="kc">null</span><span class="o">){</span>
<span class="nc">HttpServletRequest</span> <span class="n">req</span> <span class="o">=</span> <span class="o">(</span><span class="nc">HttpServletRequest</span><span class="o">)</span><span class="n">httpRequestCreator</span><span class="o">.</span><span class="na">createContextArg</span><span class="o">(</span><span class="n">invocation</span><span class="o">);</span>
<span class="nc">System</span><span class="o">.</span><span class="na">out</span><span class="o">.</span><span class="na">println</span><span class="o">(</span><span class="n">req</span><span class="o">.</span><span class="na">getRemoteHost</span><span class="o">());</span>
<span class="o">}</span>
</code></pre></div> </div>
<p>实际场景是拿最外层的地址，所以应该是LB传入到edgeservice，edgeService再放到context外下传递。</p>
</li>
<li>
<p><strong>Q: ServiceComb不支持泛型</strong></p>
<p>A: 明确不支持，需要修改接口，接口修改后需要修改版本号，以免consumer还是使用旧的版本。</p>
</li>
<li>
<p><strong>Q: ServiceComb对handler描述</strong></p>
<p>A: consumer默认的handler是simpleLB，没有配置的时候handler链会使用这个，如果配置了handler，里面一定要包含lb的handler，否则调用报错，需要在文档里面进行说明。</p>
</li>
<li>
<p><strong>Q: ServiceComb日志替换</strong></p>
<p>A: CSE java-chassis日志推荐方式是在启动的时候使用Log4jUtils.init()，直接使用推荐的Log4j来做日志管理，但是有些场景不想用log4j，比如想使用log4j2或者logback，下面以log4j2为例简单介绍下步骤：</p>
<ol>
<li>在代码里面不要使用Log4jUtils.init()；</li>
<li>去掉log4j的配置文件（不删掉也没关系，因为不会使用）；</li>
<li>exclude掉CSE框架引入的log4j，例如：
<div class="language-xml highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="nt">&lt;dependency&gt;</span>
<span class="nt">&lt;groupId&gt;</span>org.apache.servicecomb<span class="nt">&lt;/groupId&gt;</span>
<span class="nt">&lt;artifactId&gt;</span>provider-springmvc<span class="nt">&lt;/artifactId&gt;</span>
<span class="nt">&lt;exclusions&gt;</span>
<span class="nt">&lt;exclusion&gt;</span>
<span class="nt">&lt;groupId&gt;</span>log4j<span class="nt">&lt;/groupId&gt;</span>
<span class="nt">&lt;artifactId&gt;</span>log4j<span class="nt">&lt;/artifactId&gt;</span>
<span class="nt">&lt;/exclusion&gt;</span>
<span class="nt">&lt;/exclusions&gt;</span>
<span class="nt">&lt;/dependency&gt;</span>
</code></pre></div> </div>
</li>
<li>
<p>引入log4j2的依赖</p>
<div class="language-xml highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="nt">&lt;dependency&gt;</span>
<span class="nt">&lt;groupId&gt;</span>org.apache.logging.log4j<span class="nt">&lt;/groupId&gt;</span>
<span class="nt">&lt;artifactId&gt;</span>log4j-slf4j-impl<span class="nt">&lt;/artifactId&gt;</span>
<span class="nt">&lt;/dependency&gt;</span>
<span class="nt">&lt;dependency&gt;</span>
<span class="nt">&lt;groupId&gt;</span>org.apache.logging.log4j<span class="nt">&lt;/groupId&gt;</span>
<span class="nt">&lt;artifactId&gt;</span>log4j-api<span class="nt">&lt;/artifactId&gt;</span>
<span class="nt">&lt;/dependency&gt;</span>
<span class="nt">&lt;dependency&gt;</span>
<span class="nt">&lt;groupId&gt;</span>org.apache.logging.log4j<span class="nt">&lt;/groupId&gt;</span>
<span class="nt">&lt;artifactId&gt;</span>log4j-core<span class="nt">&lt;/artifactId&gt;</span>
<span class="nt">&lt;/dependency&gt;</span>
</code></pre></div> </div>
<p>如果没有版本依赖管理，还需要填写上版本号。</p>
</li>
<li>
<p>加入log4j2的配置文件log4j2.xml，关于这个请查看官方说明，例如：</p>
<div class="language-xml highlighter-rouge"><div class="highlight"><pre class="highlight"><code> <span class="cp">&lt;?xml version="1.0" encoding="UTF-8"?&gt;</span>
<span class="c">&lt;!--日志级别以及优先级排序: OFF &gt; FATAL &gt; ERROR &gt; WARN &gt; INFO &gt; DEBUG &gt; TRACE &gt; ALL --&gt;</span>
<span class="c">&lt;!--Configuration后面的status，这个用于设置log4j2自身内部的信息输出，可以不设置，当设置成trace时，你会看到log4j2内部各种详细输出--&gt;</span>
<span class="c">&lt;!--monitorInterval：Log4j能够自动检测修改配置 文件和重新配置本身，设置间隔秒数--&gt;</span>
<span class="nt">&lt;configuration</span> <span class="na">status=</span><span class="s">"WARN"</span> <span class="na">monitorInterval=</span><span class="s">"30"</span><span class="nt">&gt;</span>
<span class="c">&lt;!--先定义所有的appender--&gt;</span>
<span class="nt">&lt;appenders&gt;</span>
<span class="c">&lt;!--这个输出控制台的配置--&gt;</span>
<span class="nt">&lt;console</span> <span class="na">name=</span><span class="s">"Console"</span> <span class="na">target=</span><span class="s">"SYSTEM_OUT"</span><span class="nt">&gt;</span>
<span class="c">&lt;!--输出日志的格式--&gt;</span>
<span class="nt">&lt;PatternLayout</span> <span class="na">pattern=</span><span class="s">"[%d{HH:mm:ss:SSS}] [%p] - %l - %m%n"</span><span class="nt">/&gt;</span>
<span class="nt">&lt;/console&gt;</span>
<span class="c">&lt;!--文件会打印出所有信息，这个log每次运行程序会自动清空，由append属性决定，这个也挺有用的，适合临时测试用--&gt;</span>
<span class="nt">&lt;File</span> <span class="na">name=</span><span class="s">"log"</span> <span class="na">fileName=</span><span class="s">"log/test.log"</span> <span class="na">append=</span><span class="s">"false"</span><span class="nt">&gt;</span>
<span class="nt">&lt;PatternLayout</span> <span class="na">pattern=</span><span class="s">"%d{HH:mm:ss.SSS} %-5level %class{36} %L %M - %msg%xEx%n"</span><span class="nt">/&gt;</span>
<span class="nt">&lt;/File&gt;</span>
<span class="c">&lt;!-- 这个会打印出所有的info及以下级别的信息，每次大小超过size，则这size大小的日志会自动存入按年份-月份建立的文件夹下面并进行压缩，作为存档--&gt;</span>
<span class="nt">&lt;RollingFile</span> <span class="na">name=</span><span class="s">"RollingFileInfo"</span> <span class="na">fileName=</span><span class="s">"${sys:user.home}/logs/info.log"</span>
<span class="na">filePattern=</span><span class="s">"${sys:user.home}/logs/$${date:yyyy-MM}/info-%d{yyyy-MM-dd}-%i.log"</span><span class="nt">&gt;</span>
<span class="c">&lt;!--控制台只输出level及以上级别的信息（onMatch），其他的直接拒绝（onMismatch）--&gt;</span>
<span class="nt">&lt;ThresholdFilter</span> <span class="na">level=</span><span class="s">"info"</span> <span class="na">onMatch=</span><span class="s">"ACCEPT"</span> <span class="na">onMismatch=</span><span class="s">"DENY"</span><span class="nt">/&gt;</span>
<span class="nt">&lt;PatternLayout</span> <span class="na">pattern=</span><span class="s">"[%d{HH:mm:ss:SSS}] [%p] - %l - %m%n"</span><span class="nt">/&gt;</span>
<span class="nt">&lt;Policies&gt;</span>
<span class="nt">&lt;TimeBasedTriggeringPolicy/&gt;</span>
<span class="nt">&lt;SizeBasedTriggeringPolicy</span> <span class="na">size=</span><span class="s">"100 MB"</span><span class="nt">/&gt;</span>
<span class="nt">&lt;/Policies&gt;</span>
<span class="nt">&lt;/RollingFile&gt;</span>
<span class="nt">&lt;RollingFile</span> <span class="na">name=</span><span class="s">"RollingFileWarn"</span> <span class="na">fileName=</span><span class="s">"${sys:user.home}/logs/warn.log"</span>
<span class="na">filePattern=</span><span class="s">"${sys:user.home}/logs/$${date:yyyy-MM}/warn-%d{yyyy-MM-dd}-%i.log"</span><span class="nt">&gt;</span>
<span class="nt">&lt;ThresholdFilter</span> <span class="na">level=</span><span class="s">"warn"</span> <span class="na">onMatch=</span><span class="s">"ACCEPT"</span> <span class="na">onMismatch=</span><span class="s">"DENY"</span><span class="nt">/&gt;</span>
<span class="nt">&lt;PatternLayout</span> <span class="na">pattern=</span><span class="s">"[%d{HH:mm:ss:SSS}] [%p] - %l - %m%n"</span><span class="nt">/&gt;</span>
<span class="nt">&lt;Policies&gt;</span>
<span class="nt">&lt;TimeBasedTriggeringPolicy/&gt;</span>
<span class="nt">&lt;SizeBasedTriggeringPolicy</span> <span class="na">size=</span><span class="s">"100 MB"</span><span class="nt">/&gt;</span>
<span class="nt">&lt;/Policies&gt;</span>
<span class="c">&lt;!-- DefaultRolloverStrategy属性如不设置，则默认为最多同一文件夹下7个文件，这里设置了20 --&gt;</span>
<span class="nt">&lt;DefaultRolloverStrategy</span> <span class="na">max=</span><span class="s">"20"</span><span class="nt">/&gt;</span>
<span class="nt">&lt;/RollingFile&gt;</span>
<span class="nt">&lt;RollingFile</span> <span class="na">name=</span><span class="s">"RollingFileError"</span> <span class="na">fileName=</span><span class="s">"${sys:user.home}/logs/error.log"</span>
<span class="na">filePattern=</span><span class="s">"${sys:user.home}/logs/$${date:yyyy-MM}/error-%d{yyyy-MM-dd}-%i.log"</span><span class="nt">&gt;</span>
<span class="nt">&lt;ThresholdFilter</span> <span class="na">level=</span><span class="s">"error"</span> <span class="na">onMatch=</span><span class="s">"ACCEPT"</span> <span class="na">onMismatch=</span><span class="s">"DENY"</span><span class="nt">/&gt;</span>
<span class="nt">&lt;PatternLayout</span> <span class="na">pattern=</span><span class="s">"[%d{HH:mm:ss:SSS}] [%p] - %l - %m%n"</span><span class="nt">/&gt;</span>
<span class="nt">&lt;Policies&gt;</span>
<span class="nt">&lt;TimeBasedTriggeringPolicy/&gt;</span>
<span class="nt">&lt;SizeBasedTriggeringPolicy</span> <span class="na">size=</span><span class="s">"100 MB"</span><span class="nt">/&gt;</span>
<span class="nt">&lt;/Policies&gt;</span>
<span class="nt">&lt;/RollingFile&gt;</span>
<span class="nt">&lt;/appenders&gt;</span>
<span class="c">&lt;!--然后定义logger，只有定义了logger并引入的appender，appender才会生效--&gt;</span>
<span class="nt">&lt;loggers&gt;</span>
<span class="c">&lt;!--过滤掉spring和mybatis的一些无用的DEBUG信息--&gt;</span>
<span class="nt">&lt;logger</span> <span class="na">name=</span><span class="s">"org.springframework"</span> <span class="na">level=</span><span class="s">"INFO"</span><span class="nt">&gt;&lt;/logger&gt;</span>
<span class="nt">&lt;logger</span> <span class="na">name=</span><span class="s">"org.mybatis"</span> <span class="na">level=</span><span class="s">"INFO"</span><span class="nt">&gt;&lt;/logger&gt;</span>
<span class="nt">&lt;root</span> <span class="na">level=</span><span class="s">"all"</span><span class="nt">&gt;</span>
<span class="nt">&lt;appender-ref</span> <span class="na">ref=</span><span class="s">"Console"</span><span class="nt">/&gt;</span>
<span class="nt">&lt;appender-ref</span> <span class="na">ref=</span><span class="s">"RollingFileInfo"</span><span class="nt">/&gt;</span>
<span class="nt">&lt;appender-ref</span> <span class="na">ref=</span><span class="s">"RollingFileWarn"</span><span class="nt">/&gt;</span>
<span class="nt">&lt;appender-ref</span> <span class="na">ref=</span><span class="s">"RollingFileError"</span><span class="nt">/&gt;</span>
<span class="nt">&lt;/root&gt;</span>
<span class="nt">&lt;/loggers&gt;</span>
<span class="nt">&lt;/configuration&gt;</span>
</code></pre></div> </div>
</li>
<li>启动服务进行验证</li>
</ol>
</li>
<li>
<p><strong>Q: 服务超时设置</strong></p>
<p>A: 在微服务描述文件（microservice.yaml）中添加如下配置：</p>
<div class="language-yaml highlighter-rouge"><div class="highlight"><pre class="highlight"><code> <span class="na">servicecomb</span><span class="pi">:</span>
<span class="na">request</span><span class="pi">:</span>
<span class="na">timeout</span><span class="pi">:</span> <span class="m">30000</span>
</code></pre></div> </div>
</li>
<li>
<p><strong>Q: URL 地址就可以唯一定位，为什么要加上一个schema？</strong></p>
<p>A:</p>
<ol>
<li>schema 是用来匹配服务契约的，用来保证服务端和消费端契约兼容，每个契约需要一个唯一ID，在服务中心存储。</li>
<li>schema映射到java的interface概念，在consumer使用透明rpc模式开发时，可以找到是微服务里的哪个operation。schema之间的方法名是没有唯一性要求的。</li>
<li>operation qualified name是治理的key，而URL 因为path参数的存在，没办法直接查找，而qualified name是不会变的。治理是不区分传输的，如果治理按URL 走，那么highway调进来时，还得根据参数反向构造出url，再来正则表达式匹配，太折腾了。</li>
<li>http只是一种传输通道，还有别的传输通道不需要映射到URL的。</li>
</ol>
</li>
<li>
<p><strong>Q: rest客户端调用的时候，实际上只带上了服务名和URL，并不需要指定schema id的， 而实际上根据这个URL也能找到具体契约的，所以指定schema id作用何在？</strong></p>
<p>A: 由于透明rpc是接口式调用，并没有URL，内部实际都归一化到operation来描述的，这样就可以结合schema id唯一定位到具体的请求处理中。</p>
</li>
<li>
<p><strong>Q: Transport是个什么概念？用来干什么的？</strong></p>
<p>A: transport负责编解码，以及传输。通信模型有rest和highway两种，highway对应的是私有协议，使用protobuf编码，rest用的是json。highway和rest都是基于vertx做的，vertx是基于netty的。</p>
</li>
<li>
<p><strong>Q: 框架中引入了vertx会有什么好处？</strong></p>
<p>A: 启用vertx的标准工作模式更强大，不过对业务人员要求就有些高了，目前还没开放业务接口出来。vertx标准的reactive工作模式，要求业务代码中不能有任何的block wait,sleep，大循环，总之不能有阻塞，做到这一点，就可以用更少的CPU，提供更多的服务。</p>
</li>
<li>
<p><strong>Q: 一个服务提供者里面会有多个 appid 和微服务吗？什么场景会出现这种情况？</strong></p>
<p>A: 会，这里表达的是一个merge的概念。microservice.yaml文件，可能同时存在于jar，磁盘，命令行参数指定这几个地方，此时他们按优先级合并，是用于增加灵活性的。在jar里的是默认值，在此之外，还有环境变量，命令行参数，配置中心覆盖，提供多层定制。</p>
</li>
<li>
<p><strong>Q: ServiceComb和服务中心是怎么交互的?</strong></p>
<p>A: 走rest，主要负责注册，取数据和心跳等；watch事件走websocket，watch事件是观察服务中心实例信息有没有变更。</p>
</li>
<li>
<p><strong>Q: 有类似dubbo那种治理中心吗？</strong></p>
<p>A: bizkeeper是一个handler，是治理的其中一个内容。治理可以通过handler扩展。</p>
</li>
<li>
<p><strong>Q: service path怎么理解？</strong></p>
<p>A: 每个微服务有一个servicePathManager，每一个schema将自己的path注册进去。</p>
</li>
<li>
<p><strong>Q: 浏览器能直接访问微服务Endpoint吗？</strong></p>
<p>A: 可以，restful发布的微服务Endpoint，可以直接在浏览器中使用HTTP加service path访问提供get方法的服务，如果是访问其他Http方法提供的服务建议安装使用<a href="https://www.sap.com/developer/tutorials/api-tools-postman-install.html">Postman</a>。</p>
</li>
<li>
<p><strong>Q: 契约生成时，需要强制带上版本号和语言吗？</strong></p>
<p>A: 契约是属于微服务的，微服务本来就有版本，但语言是不应该带上版本号的。应该契约要求与语言无关。契约“没有版本”，契约的版本体现在微服务上，实例能找到所属的微服务的版本，就能找到一个确定的契约。</p>
</li>
<li>
<p><strong>Q: ServiceRegistry里的设计代码和Eureka很类似？</strong></p>
<p>A: 我们第一个版本就是在Spring Cloud的基础上做的 后来随着发展发现不够用了才逐渐自己做的一套，所以的确是在充分参考Eureka后设计的。</p>
</li>
<li>
<p><strong>Q: 有些rpc是netty调用redis实现，比直接netty转发优势在哪里？</strong></p>
<p>A: 可能是想用redis解决订阅发布吧。但这样意义也不大，之前也尝试过这么用，但后来都改成ServiceComb了。</p>
</li>
<li>
<p><strong>Q: 如果同时引入了<code class="language-plaintext highlighter-rouge">transport-rest-servlet</code>和<code class="language-plaintext highlighter-rouge">transport-rest-vertx</code>的依赖，那么它怎么决定采用哪一个？</strong></p>
<p>A: 如果端口没被占用，就用vertx；如果被占用了，就用servlet。</p>
</li>
<li>
<p><strong>Q: qps流控设计时是出于什么场景考虑的？</strong></p>
<p>A: 限流有两个主要作用，第一通过给不同的消费者限流保证对一些重点服务的服务效果，第二防止雪崩效应。可根据服务的重要性来决定水管的粗细，ServiceComb是支持消费端限流和服务端限流两种限流方式的，消费端限流可以做到比较精细的控制。</p>
</li>
<li>
<p><strong>Q: 如果服务端是链式调用，即类似a-&gt;b-&gt;c，那设置了qps 流控会不会造成水管粗细不均的事情？</strong></p>
<p>A: 一般采取的模式是先测量再设置。qps设置最终是结合整体业务需求来进行调控的，而不是就单个节点来进行设置。</p>
</li>
<li>
<p><strong>Q: 通过cse://serviceName/appPath调用服务失败，报错:java.lang.Error:not support def type:class io.swagger.models.properties xxx</strong></p>
<p>A: 检查consumer和provider依赖的java-chassis版本是否一致，如果不一致请修改并使用较新版本。</p>
</li>
<li>
<p><strong>Q: 发送rest请求时，出现如下报错：Bad Request,description:http:request body too large</strong></p>
<p>A: 检查Service Center是否老版本，如果是，则升级到最新版本。</p>
</li>
<li>
<p><strong>Q: 如何在契约DTO中忽略中指定的属性？</strong></p>
<p>A: 如果是使用rest transport，因为是Json序列化，可以使用@JsonIgnore注解标记需要忽略的属性；highway transport目前尚不支持。注意修改后需要更新微服务的version，例如:</p>
<div class="language-java highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="kd">public</span> <span class="kd">class</span> <span class="nc">OutputForTest</span><span class="o">{</span>
<span class="nd">@JsonIgnore</span>
<span class="kd">private</span> <span class="nc">String</span> <span class="n">outputId</span> <span class="o">=</span> <span class="kc">null</span><span class="o">;</span>
<span class="kd">private</span> <span class="nc">String</span> <span class="n">inputId</span> <span class="o">=</span> <span class="kc">null</span><span class="o">;</span>
<span class="o">...</span>
<span class="o">}</span>
</code></pre></div> </div>
</li>
<li>
<p><strong>Q: 如何在用户自定义的handler中获取header中某个字段的值</strong></p>
<p>A: Invocation.getArgs可以获取到接口定义里面声明的所有参数信息。在接口里面未定义的信息，比如额外的header，则需要通过InvocationContext来传递和获取。基本原理是实现HttpServerFilter将header设置到InvocationContext里面，然后在通过invocation.getContext获取。示例代码可以参考servicecomb-fence的 <a href="https://github.com/apache/servicecomb-fence/tree/master/api/edge-service/endpoint/src/main/java/org/apache/servicecomb/authentication/edge">AuthHandler 和 AuthenticationFilter</a> 。</p>
</li>
<li>
<p><strong>Q: 微服务运行时抛出异常：<code class="language-plaintext highlighter-rouge"> java.lang.Error:not support def type:calss io.swagger.models.properties BaseIntegerProperty</code>？</strong></p>
<p>A: 可将Service Center升级至最新版本来解决。<a href="http://servicecomb.apache.org/cn/release/">ServiceComb版本下载传送门</a>。</p>
</li>
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