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搭建prometheus环境监控Java应用服务，发现报错：

expected a valid start token, got "\"" ("INVALID") while parsing:

请求http://localhost:8080/actuator/prometheus：格式错乱

正常格式应该如下：

经排查发现是因为项目中配置了fastjson转换导致

public class WebMvcConfig extends WebMvcConfigurationSupport {
    @Override
    public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
        super.configureMessageConverters(converters);
        FastJsonHttpMessageConverter fastConverter = new FastJsonHttpMessageConverter();

        FastJsonConfig fastJsonConfig = new FastJsonConfig();
        fastJsonConfig.setSerializerFeatures(SerializerFeature.WriteNullListAsEmpty, SerializerFeature.WriteMapNullValue,
                SerializerFeature.WriteNullStringAsEmpty);
        fastJsonConfig.setDateFormat("yyyy-MM-dd HH:mm:ss");
        fastConverter.setFastJsonConfig(fastJsonConfig);
        List<MediaType> supportedMediaTypes = new ArrayList<>();
        supportedMediaTypes.add(MediaType.ALL);
        fastConverter.setSupportedMediaTypes(supportedMediaTypes);
        converters.add(fastConverter);
    }
}

解决方案：

• 注释上面转换代码（简单粗暴，如果影响别的地方，建议采用第二种方案）
• 配置自定义接口进行反序列化成原来格式

@RestController
@RequestMapping("prometheus")
public class PrometheusController {

    @Value("${server.servlet.context-path}")
    private String contextPath;
    @Value("${server.port}")
    private Integer port;
    @Value("${prometheus.url}")
    private Integer url;

    @GetMapping(path = "/metrics", produces = MediaType.TEXT_PLAIN_VALUE)
    public void metrics(HttpServletResponse response) {
        RestTemplate restTemplate = new RestTemplate();
        StringBuilder prometheusUrl = new StringBuilder(url);
        prometheusUrl.append(port);
        prometheusUrl.append(contextPath);
        prometheusUrl.append("/actuator/prometheus");
        ResponseEntity<String> responseEntity = restTemplate.getForEntity(prometheusUrl.toString(), String.class);
        String body = responseEntity.getBody();
        String s = JSON.parseObject(body, String.class);
        try (BufferedOutputStream bos = new BufferedOutputStream(response.getOutputStream())) {
            bos.write(s.getBytes());
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

prometheus.yml配置

  - job_name: "demo-boot"
    metrics_path: "actuator/prometheus"
    static_configs:
      - targets: ["localhost:8080"]   

改成：

  - job_name: "demo-boot"
    metrics_path: "prometheus/metrics"
    static_configs:
      - targets: ["localhost:8080"]   

 重启prometheus：

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