pushing metrics to prometheus pushgateway response 400

[zhangcughnu]

Bug Report

What did you do?
After springboot is upgraded from 2.3.4 to 2.7.18, 400 metric is pushed. The metric is normal before SpringBoot is upgraded, and the following error logs are reported:

• Pushgateway version:

    pushgateway version : 1.4.3
  

• Java dependency
  spring-boot-starter-actuator : 2.7.18
  micrometer-registry-prometheus : 1.9.17
  simpleclient_pushgateway : 0.16.0

• Logs:
  java excpetion log:
  resonse code from http://**/metrics/job/ . was 400, response body: pushed metrics are invalid or inconsistent with existing metrics : 15 erros occurred:

• collected metric "jvm_classes_unloaded_classes_total" {lable:<name:"instance" value:"" lable:<name:"job" value:"**"> counter:value:0} is not a untyped.