背景

基于springboot的微服務進行系統(tǒng)監(jiān)控改造，在現(xiàn)有的erueka+actuator基礎上拓展Prometheus進行更多指標的系統(tǒng)監(jiān)控，能在服務不可用前進行告警

引入依賴

actuator的依賴+Prometheus的register的依賴

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-actuator</artifactId>
</dependency>
<dependency>
    <groupId>io.micrometer</groupId>
    <artifactId>micrometer-registry-prometheus</artifactId>
</dependency>

配置只暴露Pormetheus的端口，metric tag的配置個人覺得沒有必要

management:
  endpoints:
    web.exposure.include: prometheus

到了這里之后正常GET請求 ip:port/{servlet.context-path}/actuator/prometheus
就會得到這樣的回復(只截取了一點)
Content-Type:text/plain; version=0.0.4;charset=utf-8

# HELP system_cpu_usage The "recent cpu usage" for the whole system
# TYPE system_cpu_usage gauge
system_cpu_usage 0.0
# HELP process_start_time_seconds Start time of the process since unix epoch.
# TYPE process_start_time_seconds gauge
process_start_time_seconds 1.606481846248E9

然而在實際的過程中卻出現(xiàn)了406錯誤

{
    "timestamp": "",
    "status": 406,
    "error": "Not Acceptable",
    "message": "Could not find acceptable representation",
    "path": "/actuator/prometheus",
}

搜了網(wǎng)上的答案說因為缺失MediaType(Text/Plain)導致無法解析
因為項目中自定義了HttpMessageConverter，加入了MappingJackson2HttpMessageConverter，而其默認方法只加載了MediaType Application/Json,一度以為問題就結(jié)束了，在為MappingJackson2HttpMessageConverter添加了Text/Plain的支持后，能得到格式不正確的回復(換行被轉(zhuǎn)義為\n)

"# HELP jvm_memory_used_bytes The amount of used memory\n# TYPE jvm_memory_used_bytes gauge\njvm_memory_used_bytes{area=\"heap\",id=\"PS Survivor Space\",} 0.0\njvm_memory_used_bytes{area=\"heap\",id=\"PS Old Gen\",} 3.9645672E7\njvm_memory_used_bytes{area=\"heap\",id=\"PS Eden Space\",} 1.77528552E8\njvm_memory_used_bytes{area=\"nonheap\",id=\"Metaspace\",} 6.9426912E7\njvm_memory_used_bytes{area=\"nonheap\",id=\"Code Cache\",} 1.302752E7\njvm_memory_used_bytes{area=\"nonheap\",id=\"Compressed Class Space\",} 9426568.0\n

顯然這不是增加一個MediaType能解決的問題，推測應該是該類所需的MessageConvertor沒有被加載，導致?lián)Q行被錯誤的轉(zhuǎn)義。
因為數(shù)據(jù)的寫入類是通過寫入char(32)進行換行操作的，按道理說應該是會被正確的轉(zhuǎn)義，于是將重寫的類注釋掉后運行能得到正確的答案，這就確立的問題排查的方向，找出所需的convertor進行手動加載。項目中的MessageConvertor是基于WebMvcConfigurationSupport進行重寫的
然而Spring框架的拓展更多是以Adapter為結(jié)尾的

public class WebMvcConfigurationSupport implements ApplicationContextAware, ServletContextAware {
/**
     * Adds a set of default HttpMessageConverter instances to the given list.
     * Subclasses can call this method from {@link #configureMessageConverters}.
     * @param messageConverters the list to add the default message converters to
     */
    protected final void addDefaultHttpMessageConverters(List<HttpMessageConverter<?>> messageConverters) {
        StringHttpMessageConverter stringHttpMessageConverter = new StringHttpMessageConverter();
        stringHttpMessageConverter.setWriteAcceptCharset(false);  // see SPR-7316

        messageConverters.add(new ByteArrayHttpMessageConverter());
        messageConverters.add(stringHttpMessageConverter);
        messageConverters.add(new ResourceHttpMessageConverter());
        messageConverters.add(new ResourceRegionHttpMessageConverter());
        try {
            messageConverters.add(new SourceHttpMessageConverter<>());
        }
        catch (Throwable ex) {
            // Ignore when no TransformerFactory implementation is available...
        }
        messageConverters.add(new AllEncompassingFormHttpMessageConverter());

        if (romePresent) {
            messageConverters.add(new AtomFeedHttpMessageConverter());
            messageConverters.add(new RssChannelHttpMessageConverter());
        }

        if (jackson2XmlPresent) {
            Jackson2ObjectMapperBuilder builder = Jackson2ObjectMapperBuilder.xml();
            if (this.applicationContext != null) {
                builder.applicationContext(this.applicationContext);
            }
            messageConverters.add(new MappingJackson2XmlHttpMessageConverter(builder.build()));
        }
        else if (jaxb2Present) {
            messageConverters.add(new Jaxb2RootElementHttpMessageConverter());
        }

        if (jackson2Present) {
            Jackson2ObjectMapperBuilder builder = Jackson2ObjectMapperBuilder.json();
            if (this.applicationContext != null) {
                builder.applicationContext(this.applicationContext);
            }
            messageConverters.add(new MappingJackson2HttpMessageConverter(builder.build()));
        }
        else if (gsonPresent) {
            messageConverters.add(new GsonHttpMessageConverter());
        }
        else if (jsonbPresent) {
            messageConverters.add(new JsonbHttpMessageConverter());
        }

        if (jackson2SmilePresent) {
            Jackson2ObjectMapperBuilder builder = Jackson2ObjectMapperBuilder.smile();
            if (this.applicationContext != null) {
                builder.applicationContext(this.applicationContext);
            }
            messageConverters.add(new MappingJackson2SmileHttpMessageConverter(builder.build()));
        }
        if (jackson2CborPresent) {
            Jackson2ObjectMapperBuilder builder = Jackson2ObjectMapperBuilder.cbor();
            if (this.applicationContext != null) {
                builder.applicationContext(this.applicationContext);
            }
            messageConverters.add(new MappingJackson2CborHttpMessageConverter(builder.build()));
        }
    }
}

可以在沒有重寫情況下，框架會寫入一定數(shù)量的MessageConvertor，而因為項目中的重寫導致Prometheus所需的convertor沒有被加載，經(jīng)過一系列的排查，最終鎖定了

StringHttpMessageConverter stringHttpMessageConverter = new StringHttpMessageConverter();
        stringHttpMessageConverter.setWriteAcceptCharset(false);

于是在重寫的方法中加上該轉(zhuǎn)換器后問題得到了解決。

因此引申出來的思考

WebMvcConfigurationSupport與WebMvcConfigurer的區(qū)別
如果要在spring的基礎上拓展可以implements WebMvcConfigurer，
相反 如果想要一個純凈的環(huán)境，那么可以直接覆蓋WebMvcConfigurationSupport
ProMetheus的配置等下一章吧。