java - Micrometer - Prometheus Gauge 显示 NaN

Question

我正在尝试通过将 Micrometer.io 与 Spring Boot 2.0.0.RELEASE 结合使用来生成 Prometheus 指标。

当我尝试将 List 的大小时公开为 Gauge 时，它​​一直显示 NaN。在文档中它说；

It is your responsibility to hold a strong reference to the state object that you are measuring with a Gauge.

我尝试了一些不同的方法，但我无法解决问题。这是我的一些试验代码。

import io.micrometer.core.instrument.*;
import io.swagger.backend.model.Product;
import io.swagger.backend.service.ProductService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;

import java.util.List;
import java.util.concurrent.atomic.AtomicInteger;

@RestController
@RequestMapping("metrics")
public class ExampleController {

    private AtomicInteger atomicInteger = new AtomicInteger();

    private ProductService productService;
    private final Gauge productGauge;

    @Autowired
    public HelloController(ProductService productService,
                           MeterRegistry registry) {

        this.productService = productService;

        createGauge("product_gauge", productService.getProducts(), registry);
    }

    private void createGauge(String metricName, List<Product> products,
                                    MeterRegistry registry) {

        List<Product> products = productService.getProducts();

        // #1
        // this displays product_gauge as NaN
        AtomicInteger n = registry.gauge("product_gauge", new AtomicInteger(0));
        n.set(1);
        n.set(2);

        // #2
        // this also displays product_gauge as NaN
        Gauge
            .builder("product_gauge", products, List::size)
            .register(registry);

        // #3
        // this displays also NaN
        testListReference = Arrays.asList(1, 2);
        Gauge
            .builder("random_gauge", testListReference, List::size)
            .register(registry);

        // #4
        // this also displays NaN
        AtomicInteger currentHttpRequests = registry.gauge("current.http.requests", new AtomicInteger(0));
    }

    @GetMapping(path = "/product/decrement")
    public Counter decrementAndGetProductCounter() {
        // decrement the gague by one
    }
}

有没有人可以帮助解决这个问题？任何帮助将不胜感激。

Answer 1

在所有情况下，您都必须持有对观察到的实例的强引用。当您的 createGauge() 方法退出时，所有函数堆栈分配的引用都符合垃圾回收条件。

对于 #1，像这样传递您的 atomicInteger 字段:registry.gauge("my_ai", atomicInteger);。然后根据需要递增/递减。每当micrometer需要查询它的时候，只要找到引用它就会查询。

对于 #2，传递您的 productService 字段和一个 lambda。基本上，无论何时查询仪表，它都会使用提供的对象调用该 lambda:registry.gauge("product_gauge", productService, productService -> productService.getProducts().size());

(不保证语法错误。)