坑：异步调用其他服务避免使用AsyncRestTemplate

浅浅的花香味﹌ 2022-11-29 13:05 145阅读 0赞

# 现象 #

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0NhcnNvbjA3Mw_size_16_color_FFFFFF_t_70][]

订单服务的几个流程推动接口，出现了大量异常。持续20分钟。

# 排查 #

初步查看日志，发现这段时间有大量异常抛出，全部都是

java.lang.IllegalStateException: No instances available for travel-push。如图：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0NhcnNvbjA3Mw_size_16_color_FFFFFF_t_70 1][]

比较奇怪的是push全都是异步调用的。按理说不能影响到主流程才对。

查代码发现，用的异步调用，是用的org.springframework.web.client.AsyncRestTemplate

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0NhcnNvbjA3Mw_size_16_color_FFFFFF_t_70 2][]

AsyncRestTemplate这个还是标注成废弃的

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0NhcnNvbjA3Mw_size_16_color_FFFFFF_t_70 3][]

AsyncRestTemplate处理异步层面比较靠近调用，所以当被调用服务不可达的时候，这里会抛出异常，还是挺危险的。

并且这种方式不能传递traceId。

# 结论 #

可以自己写异步替代AsyncRestTemplate，利用CompletableFuture显式处理成功和失败。

同时可以指定executor来传递traceId。详见 [异步线程带上traceId][traceId]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0NhcnNvbjA3Mw_size_16_color_FFFFFF_t_70 4][]

附：[异步线程带上traceId][traceId]

我们在做异步处理的时候。用logger打日志以及http跨模块调用时，traceId都会因为线程改变而丢失原来的跟踪信息。在排查问题看日志时很不方便。

traceId其实是腾讯tsf基于spring cloud sleuth搞的，是trace和span中trace的id。

在其官方文档中，提供了几种异步传递trace/span的机制。

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0NhcnNvbjA3Mw_size_16_color_FFFFFF_t_70 5][]

原地址：[https://cloud.spring.io/spring-cloud-sleuth/reference/html/\#asynchronous-communication][https_cloud.spring.io_spring-cloud-sleuth_reference_html_asynchronous-communication]

举个例子，

我们比较常用的是通过executor去创建一个异步线程，可以用LazyTraceExecutor去包装这个executor即可。

首先根据需要的场景，指定线程数等参数配置一个executor的bean。

<table> 
 <tbody> 
 <tr> 
 <td> <code>@Bean</code><code>(name =&nbsp;</code><code>"myExecutorService"</code><code>)</code> <code>public</code>&nbsp;<code>Executor getMyExecutorService() { </code> <code>&nbsp;&nbsp;&nbsp;&nbsp;</code><code>BasicThreadFactory threadFactory =&nbsp;</code><code>new</code>&nbsp;<code>BasicThreadFactory.Builder()</code> <code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code><code>.namingPattern(</code><code>"shunfeng-pool-%d"</code><code>)</code> <code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code><code>.daemon(</code><code>true</code><code>)</code> <code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code><code>.build();</code> &nbsp; <code>&nbsp;&nbsp;&nbsp;&nbsp;</code><code>ThreadPoolExecutor threadPoolExecutor =</code> <code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code><code>new</code>&nbsp;<code>ThreadPoolExecutor(threadPoolConfig.getCorePoolSize(),</code> <code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code><code>threadPoolConfig.getMaxPoolSize(),</code> <code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code><code>threadPoolConfig.getKeepAliveSeconds(),</code> <code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code><code>TimeUnit.SECONDS,</code> <code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code><code>new</code>&nbsp;<code>LinkedBlockingQueue&lt;&gt;(</code><code>1024</code><code>),</code> <code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code><code>threadFactory,</code> <code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code><code>new</code>&nbsp;<code>ThreadPoolExecutor.AbortPolicy());</code> &nbsp; <code>&nbsp;&nbsp;&nbsp;&nbsp;</code><code>return</code>&nbsp;<code>new</code>&nbsp;<code>LazyTraceExecutor(beanFactory, threadPoolExecutor);</code> <code>}</code> </td> 
 </tr> 
 </tbody> 
</table>

在需要的地方注入，然后按原来的方式使用即可。

<table> 
 <tbody> 
 <tr> 
 <td> <code>@Autowired</code> <code>@Qualifier</code><code>(</code><code>"myExecutorService"</code><code>)</code> <code>Executor executor;</code> &nbsp; &nbsp; <code>private</code>&nbsp;<code>void</code>&nbsp;<code>asyncDoSomething1() { </code> <code>&nbsp;&nbsp;&nbsp;&nbsp;</code><code>log.info(</code><code>"async."</code><code>);</code> <code>&nbsp;&nbsp;&nbsp;&nbsp;</code><code>CompletableFuture.runAsync(() -&gt; doSomething(), executor);</code> <code>}</code> &nbsp; <code>private</code>&nbsp;<code>void</code>&nbsp;<code>asyncDoSomething2() { </code> <code>&nbsp;&nbsp;&nbsp;&nbsp;</code><code>log.info(</code><code>"async."</code><code>);</code> <code>&nbsp;&nbsp;&nbsp;&nbsp;</code><code>executor.execute(() -&gt; doSomething());</code> <code>}</code> </td> 
 </tr> 
 </tbody> 
</table>

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[traceId]: http://wiki.ruqimobility.com:8090/pages/viewpage.action?pageId=11862103
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[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0NhcnNvbjA3Mw_size_16_color_FFFFFF_t_70 5]: /images/20221124/d456c25797dc4df6ad4e9b6677d14e39.png
[https_cloud.spring.io_spring-cloud-sleuth_reference_html_asynchronous-communication]: https://cloud.spring.io/spring-cloud-sleuth/reference/html/#asynchronous-communication