定义 DemoMetrics

public class DemoMetrics implements MeterBinder {

    private AtomicLong systemMemoryUsed = new AtomicLong(0);

    //这里实现了MeterBinder接口的bindTo方法，将要采集的指标注册到MeterRegistry
    @Override
    public void bindTo(MeterRegistry meterRegistry) {
        //这里的MeterRegistry 是全局的
        Gauge.builder("system.memory.used",systemMemoryUsed, AtomicLong::get)
    //              .tag("groupName", this.groupName)
                    .description("系统已用内存（byte）")
                    .register(registry);
    }

    //定时器，定时改变内存数值
    @Scheduled(fixedRate = 1000)
    public void recordMemory(){
        //获取内存信息，省略
        //更改内存
        systemMemoryUsed.set(physicalUse);
    }
}

@Bean
public DemoMetrics demoMetrics(){
    return new DemoMetrics();
}