What would be the alternative to expose metrics endpoint for Prometheus?

Question

I would like to expose Prometheus metrics to an endpoint. I don't have spring-boot so I need to expose metrics on my own.

I took example code from:

https://micrometer.io/docs/registry/prometheus#_configuring

PrometheusMeterRegistry prometheusRegistry = new PrometheusMeterRegistry(PrometheusConfig.DEFAULT);

try {
    HttpServer server = HttpServer.create(new InetSocketAddress(8080), 0);
    server.createContext("/prometheus", httpExchange -> {
        String response = prometheusRegistry.scrape(); (1)
        httpExchange.sendResponseHeaders(200, response.getBytes().length);
        try (OutputStream os = httpExchange.getResponseBody()) {
            os.write(response.getBytes());
        }
    });

    new Thread(server::start).start();
} catch (IOException e) {
    throw new RuntimeException(e);
}

While it works, I would like to avoid using sun package. Is there a way to do this as short and elegant with netty, okhttp or apache for example?

Thank you.

Answer 1

You may use this piece of code:

Server server = new Server(8080);
ServletContextHandler context = new ServletContextHandler();
context.setContextPath("/");
server.setHandler(context);
context.addServlet(new ServletHolder(new MetricsServlet()), "/prometheus");

There are no sun packages in imports, only Jetty and Prometheus Java client :

import io.prometheus.client.exporter.MetricsServlet;
import org.eclipse.jetty.server.Server;
import org.eclipse.jetty.servlet.ServletContextHandler;
import org.eclipse.jetty.servlet.ServletHolder;

Answer 2

I am facing an issue related to below code:

PrometheusMeterRegistry prometheusRegistry = new PrometheusMeterRegistry(PrometheusConfig.DEFAULT);

try {
    HttpServer server = HttpServer.create(new InetSocketAddress(8080), 0);
    server.createContext("/prometheus", httpExchange -> {
        String response = prometheusRegistry.scrape(); (1)
        httpExchange.sendResponseHeaders(200, response.getBytes().length);
        try (OutputStream os = httpExchange.getResponseBody()) {
            os.write(response.getBytes());
        }
    });

    new Thread(server::start).start();
} catch (IOException e) {
    throw new RuntimeException(e);
}

after running code when i go to http://localhost:8080 it doesn't even connect