教程：监控 Java 应用程序

package de.spinscale.javalin;

import io.javalin.Javalin;

public class App {
    public static void main(String[] args) {
        Javalin app = Javalin.create().start(7000);
        app.get("/", ctx -> ctx.result("Appsolutely perfect"));
    }
}

package de.spinscale.javalin;

import io.javalin.Javalin;
import io.javalin.http.Handler;

public class App {

    public static void main(String[] args) {
        Javalin app = Javalin.create().start(7000);
        app.get("/", mainHandler());
    }

    static Handler mainHandler() {
        return ctx -> ctx.result("Appsolutely perfect");
    }
}

package de.spinscale.javalin;

import io.javalin.http.Context;
import org.junit.jupiter.api.Test;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.util.HashMap;

import static de.spinscale.javalin.App.mainHandler;
import static org.assertj.core.api.Assertions.assertThat;
import static org.mockito.Mockito.mock;

public class AppTests {

    final HttpServletRequest req = mock(HttpServletRequest.class);
    final HttpServletResponse res = mock(HttpServletResponse.class);
    final Context ctx = new Context(req, res, new HashMap<>());

    @Test
    public void testMainHandler() throws Exception {
        mainHandler().handle(ctx);

        String response = resultStreamToString(ctx);
        assertThat(response).isEqualTo("Appsolutely perfect");
    }

    private String resultStreamToString(Context ctx) throws IOException {
        final byte[] bytes = ctx.resultStream().readAllBytes();
        return new String(bytes, StandardCharsets.UTF_8);
    }
}

package de.spinscale.javalin;

import io.javalin.Javalin;
import io.javalin.http.Handler;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class App {

    private static final Logger logger = LoggerFactory.getLogger(App.class);

    public static void main(String[] args) {
        Javalin app = Javalin.create();
        app.get("/", mainHandler());
        app.start(7000);
    }

    static Handler mainHandler() {
        return ctx -> {
            logger.info("This is an informative logging message, user agent [{}]", ctx.userAgent());
            ctx.result("Appsolutely perfect");
        };
    }
}

public class App {

    private static final Logger logger = LoggerFactory.getLogger(App.class);

    public static void main(String[] args) {
        Javalin app = Javalin.create(config -> {
            config.requestLogger((ctx, executionTimeMs) -> {
                logger.info("{} {} {} {} \"{}\" {}",
                        ctx.method(),  ctx.url(), ctx.req.getRemoteHost(),
                        ctx.res.getStatus(), ctx.userAgent(), executionTimeMs.longValue());
           });
        });
        app.get("/", mainHandler());
        app.start(7000);
    }

    static Handler mainHandler() {
        return ctx -> {
            logger.info("This is an informative logging message, user agent [{}]", ctx.userAgent());
            ctx.result("Appsolutely perfect");
        };
    }
}

Javalin app = Javalin.create(config -> {
    config.requestLogger((ctx, executionTimeMs) -> {
        String userAgent = ctx.userAgent() != null ? ctx.userAgent() : "-";
        logger.info("{} {} {} {} \"{}\" {}",
                ctx.method(), ctx.req.getPathInfo(), ctx.res.getStatus(),
                ctx.req.getRemoteHost(), userAgent, executionTimeMs.longValue());
    });
});

static Handler mainHandler() {
    return ctx -> {
        String userAgent = ctx.userAgent() != null ? ctx.userAgent() : "-";
        logger.info("This is an informative logging message, user agent [{}]", userAgent);
        ctx.result("Appsolutely perfect");
    };
}

...
import io.javalin.plugin.metrics.MicrometerPlugin;
import io.javalin.core.security.BasicAuthCredentials;
...

Javalin app = Javalin.create(config -> {
   ...
   config.registerPlugin(new MicrometerPlugin());
);

final Micrometer micrometer = new Micrometer();
app.get("/metrics", ctx -> {
  ctx.status(404);
  if (ctx.basicAuthCredentialsExist()) {
    final BasicAuthCredentials credentials = ctx.basicAuthCredentials();
    if ("metrics".equals(credentials.getUsername()) && "secret".equals(credentials.getPassword())) {
      ctx.status(200).result(micrometer.scrape());
    }
  }
});

package de.spinscale.javalin;

import io.micrometer.core.instrument.Metrics;
import io.micrometer.core.instrument.binder.jvm.JvmCompilationMetrics;
import io.micrometer.core.instrument.binder.jvm.JvmGcMetrics;
import io.micrometer.core.instrument.binder.jvm.JvmHeapPressureMetrics;
import io.micrometer.core.instrument.binder.jvm.JvmMemoryMetrics;
import io.micrometer.core.instrument.binder.jvm.JvmThreadMetrics;
import io.micrometer.core.instrument.binder.logging.Log4j2Metrics;
import io.micrometer.core.instrument.binder.system.FileDescriptorMetrics;
import io.micrometer.core.instrument.binder.system.ProcessorMetrics;
import io.micrometer.core.instrument.binder.system.UptimeMetrics;
import io.micrometer.prometheus.PrometheusConfig;
import io.micrometer.prometheus.PrometheusMeterRegistry;

public class Micrometer {

    final PrometheusMeterRegistry registry = new PrometheusMeterRegistry(new PrometheusConfig() {
        @Override
        public String get(String key) {
            return null;
        }

        @Override
        public String prefix() {
            return "javalin";
        }
    });

    public Micrometer() {
        Metrics.addRegistry(registry);
        new JvmGcMetrics().bindTo(Metrics.globalRegistry);
        new JvmHeapPressureMetrics().bindTo(Metrics.globalRegistry);
        new JvmThreadMetrics().bindTo(Metrics.globalRegistry);
        new JvmCompilationMetrics().bindTo(Metrics.globalRegistry);
        new JvmMemoryMetrics().bindTo(Metrics.globalRegistry);
        new Log4j2Metrics().bindTo(Metrics.globalRegistry);
        new UptimeMetrics().bindTo(Metrics.globalRegistry);
        new FileDescriptorMetrics().bindTo(Metrics.globalRegistry);
        new ProcessorMetrics().bindTo(Metrics.globalRegistry);
    }

    public String scrape() {
        return registry.scrape();
    }
}

...
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.Executor;
import java.util.concurrent.TimeUnit;
...

public static void main(String[] args) {
...
    final Executor executor = CompletableFuture.delayedExecutor(20, TimeUnit.SECONDS);
    app.get("/wait", ctx -> {
        CompletableFuture<String> future = CompletableFuture.supplyAsync(() -> "done", executor);
        ctx.result(future);
    });
...

import co.elastic.apm.attach.ElasticApmAttacher;

...

public static void main(String[] args) {
    ElasticApmAttacher.attach();
    ...
}

app.before(ctx -> ElasticApm.currentTransaction()
  .setName(ctx.method() + " " + ctx.path()));

import org.apache.http.client.fluent.Request;

...

public static void main(String[] args) {
...

    app.get("/weather/:city", ctx -> {
        String city = ctx.pathParam("city");
        ctx.result(Request.Get("https://wttr.in/" + city + "?format=3").execute()
            .returnContent().asBytes())
            .contentType("text/plain; charset=utf-8");
    });

...

app.after(ctx -> ElasticApm.currentTransaction().setName(ctx.method()
  + " " + ctx.endpointHandlerPath()));

package de.spinscale.javalin;

import io.javalin.http.Context;
import io.javalin.http.RequestLogger;
import org.jetbrains.annotations.NotNull;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class Log4j2RequestLogger implements RequestLogger  {

    private final Logger logger = LoggerFactory.getLogger(Log4j2RequestLogger.class);

    @Override
    public void handle(@NotNull Context ctx, @NotNull Float executionTimeMs) throws Exception {
        String userAgent = ctx.userAgent() != null ? ctx.userAgent() : "-";
        logger.info("{} {} {} {} \"{}\" {}",
                ctx.method(), ctx.req.getPathInfo(), ctx.res.getStatus(),
                ctx.req.getRemoteHost(), userAgent, executionTimeMs.longValue());
    }
}

config.requestLogger(new Log4j2RequestLogger());