使用 API 记录遥测数据

package otel;

import io.opentelemetry.context.Context;
import io.opentelemetry.context.ContextKey;
import io.opentelemetry.context.Scope;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;

public class ContextUsage {
  public static void contextUsage() throws Exception {
    // Define an example context key
    ContextKey<String> exampleContextKey = ContextKey.named("example-context-key");

    // Context doesn't contain the key until we add it
    // Context.current() accesses the current context
    // output => current context value: null
    System.out.println("current context value: " + Context.current().get(exampleContextKey));

    // Add entry to context
    Context context = Context.current().with(exampleContextKey, "value");

    // The local context var contains the added value
    // output => context value: value
    System.out.println("context value: " + context.get(exampleContextKey));
    // The current context still doesn't contain the value
    // output => current context value: null
    System.out.println("current context value: " + Context.current().get(exampleContextKey));

    // Calling context.makeCurrent() sets Context.current() to the context until the scope is
    // closed, upon which Context.current() is restored to the state prior to when
    // context.makeCurrent() was called. The resulting Scope implements AutoCloseable and is
    // normally used in a try-with-resources block. Failure to call Scope.close() is an error and
    // may cause memory leaks or other issues.
    try (Scope scope = context.makeCurrent()) {
      // The current context now contains the added value
      // output => context value: value
      System.out.println("context value: " + Context.current().get(exampleContextKey));
    }

    // The local context var still contains the added value
    // output => context value: value
    System.out.println("context value: " + context.get(exampleContextKey));
    // The current context no longer contains the value
    // output => current context value: null
    System.out.println("current context value: " + Context.current().get(exampleContextKey));

    ExecutorService executorService = Executors.newSingleThreadExecutor();
    ScheduledExecutorService scheduledExecutorService = Executors.newScheduledThreadPool(1);

    // Context instances can be explicitly passed around application code, but it's more convenient
    // to use implicit context, calling Context.makeCurrent() and accessing via Context.current().
    // Context provides a number of utilities for implicit context propagation. These utilities wrap
    // utility classes like Scheduler, ExecutorService, ScheduledExecutorService, Runnable,
    // Callable, Consumer, Supplier, Function, etc and modify their behavior to call
    // Context.makeCurrent() before running.
    context.wrap(ContextUsage::callable).call();
    context.wrap(ContextUsage::runnable).run();
    context.wrap(executorService).submit(ContextUsage::runnable);
    context.wrap(scheduledExecutorService).schedule(ContextUsage::runnable, 1, TimeUnit.SECONDS);
    context.wrapConsumer(ContextUsage::consumer).accept(new Object());
    context.wrapConsumer(ContextUsage::biConsumer).accept(new Object(), new Object());
    context.wrapFunction(ContextUsage::function).apply(new Object());
    context.wrapSupplier(ContextUsage::supplier).get();
  }

  /** Example {@link java.util.concurrent.Callable}. */
  private static Object callable() {
    return new Object();
  }

  /** Example {@link Runnable}. */
  private static void runnable() {}

  /** Example {@link java.util.function.Consumer}. */
  private static void consumer(Object object) {}

  /** Example {@link java.util.function.BiConsumer}. */
  private static void biConsumer(Object object1, Object object2) {}

  /** Example {@link java.util.function.Function}. */
  private static Object function(Object object) {
    return object;
  }

  /** Example {@link java.util.function.Supplier}. */
  private static Object supplier() {
    return new Object();
  }
}

package otel;

import io.opentelemetry.api.baggage.propagation.W3CBaggagePropagator;
import io.opentelemetry.api.trace.propagation.W3CTraceContextPropagator;
import io.opentelemetry.context.Context;
import io.opentelemetry.context.propagation.ContextPropagators;
import io.opentelemetry.context.propagation.TextMapPropagator;
import io.opentelemetry.context.propagation.TextMapSetter;
import java.net.URI;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;

public class InjectContextUsage {
  private static final TextMapSetter<HttpRequest.Builder> TEXT_MAP_SETTER = new HttpRequestSetter();

  public static void injectContextUsage() throws Exception {
    // Create a ContextPropagators instance which propagates w3c trace context and w3c baggage
    ContextPropagators propagators =
        ContextPropagators.create(
            TextMapPropagator.composite(
                W3CTraceContextPropagator.getInstance(), W3CBaggagePropagator.getInstance()));

    // Create an HttpRequest builder
    HttpClient httpClient = HttpClient.newBuilder().build();
    HttpRequest.Builder requestBuilder =
        HttpRequest.newBuilder().uri(new URI("http://127.0.0.1:8080/resource")).GET();

    // Given a ContextPropagators instance, inject the current context into the HTTP request carrier
    propagators.getTextMapPropagator().inject(Context.current(), requestBuilder, TEXT_MAP_SETTER);

    // Send the request with the injected context
    httpClient.send(requestBuilder.build(), HttpResponse.BodyHandlers.discarding());
  }

  /** {@link TextMapSetter} with a {@link HttpRequest.Builder} carrier. */
  private static class HttpRequestSetter implements TextMapSetter<HttpRequest.Builder> {
    @Override
    public void set(HttpRequest.Builder carrier, String key, String value) {
      if (carrier == null) {
        return;
      }
      carrier.setHeader(key, value);
    }
  }
}

package otel;

import com.sun.net.httpserver.HttpExchange;
import com.sun.net.httpserver.HttpHandler;
import com.sun.net.httpserver.HttpServer;
import io.opentelemetry.api.baggage.propagation.W3CBaggagePropagator;
import io.opentelemetry.api.trace.propagation.W3CTraceContextPropagator;
import io.opentelemetry.context.Context;
import io.opentelemetry.context.Scope;
import io.opentelemetry.context.propagation.ContextPropagators;
import io.opentelemetry.context.propagation.TextMapGetter;
import io.opentelemetry.context.propagation.TextMapPropagator;
import io.opentelemetry.context.propagation.TextMapSetter;
import java.io.IOException;
import java.io.OutputStream;
import java.net.InetSocketAddress;
import java.nio.charset.StandardCharsets;
import java.util.List;

public class ExtractContextUsage {
  private static final TextMapGetter<HttpExchange> TEXT_MAP_GETTER = new HttpRequestGetter();

  public static void extractContextUsage() throws Exception {
    // Create a ContextPropagators instance which propagates w3c trace context and w3c baggage
    ContextPropagators propagators =
        ContextPropagators.create(
            TextMapPropagator.composite(
                W3CTraceContextPropagator.getInstance(), W3CBaggagePropagator.getInstance()));

    // Create a server, which uses the propagators to extract context from requests
    HttpServer server = HttpServer.create(new InetSocketAddress(8080), 0);
    server.createContext("/path", new Handler(propagators));
    server.setExecutor(null);
    server.start();
  }

  private static class Handler implements HttpHandler {
    private final ContextPropagators contextPropagators;

    private Handler(ContextPropagators contextPropagators) {
      this.contextPropagators = contextPropagators;
    }

    @Override
    public void handle(HttpExchange exchange) throws IOException {
      // Extract the context from the request and make the context current
      Context extractedContext =
          contextPropagators
              .getTextMapPropagator()
              .extract(Context.current(), exchange, TEXT_MAP_GETTER);
      try (Scope scope = extractedContext.makeCurrent()) {
        // Do work with the extracted context
      } finally {
        String response = "success";
        exchange.sendResponseHeaders(200, response.length());
        OutputStream os = exchange.getResponseBody();
        os.write(response.getBytes(StandardCharsets.UTF_8));
        os.close();
      }
    }
  }

  /** {@link TextMapSetter} with a {@link HttpExchange} carrier. */
  private static class HttpRequestGetter implements TextMapGetter<HttpExchange> {
    @Override
    public Iterable<String> keys(HttpExchange carrier) {
      return carrier.getRequestHeaders().keySet();
    }

    @Override
    public String get(HttpExchange carrier, String key) {
      if (carrier == null) {
        return null;
      }
      List<String> headers = carrier.getRequestHeaders().get(key);
      if (headers == null || headers.isEmpty()) {
        return null;
      }
      return headers.get(0);
    }
  }
}

package otel;

import io.opentelemetry.api.OpenTelemetry;
import io.opentelemetry.api.logs.Logger;
import io.opentelemetry.api.logs.LoggerProvider;
import io.opentelemetry.api.metrics.Meter;
import io.opentelemetry.api.metrics.MeterProvider;
import io.opentelemetry.api.trace.Tracer;
import io.opentelemetry.api.trace.TracerProvider;

public class ProvidersAndScopes {

  private static final String SCOPE_NAME = "fully.qualified.name";
  private static final String SCOPE_VERSION = "1.0.0";
  private static final String SCOPE_SCHEMA_URL = "https://example";

  public static void providersUsage(OpenTelemetry openTelemetry) {
    // Access providers from an OpenTelemetry instance
    TracerProvider tracerProvider = openTelemetry.getTracerProvider();
    MeterProvider meterProvider = openTelemetry.getMeterProvider();
    // NOTE: LoggerProvider is a special case and should only be used to bridge logs from other
    // logging APIs / frameworks into OpenTelemetry.
    LoggerProvider loggerProvider = openTelemetry.getLogsBridge();

    // Access tracer, meter, logger from providers to record telemetry for a particular scope
    Tracer tracer =
        tracerProvider
            .tracerBuilder(SCOPE_NAME)
            .setInstrumentationVersion(SCOPE_VERSION)
            .setSchemaUrl(SCOPE_SCHEMA_URL)
            .build();
    Meter meter =
        meterProvider
            .meterBuilder(SCOPE_NAME)
            .setInstrumentationVersion(SCOPE_VERSION)
            .setSchemaUrl(SCOPE_SCHEMA_URL)
            .build();
    Logger logger =
        loggerProvider
            .loggerBuilder(SCOPE_NAME)
            .setInstrumentationVersion(SCOPE_VERSION)
            .setSchemaUrl(SCOPE_SCHEMA_URL)
            .build();

    // ...optionally, shorthand versions are available if scope version and schemaUrl aren't
    // available
    tracer = tracerProvider.get(SCOPE_NAME);
    meter = meterProvider.get(SCOPE_NAME);
    logger = loggerProvider.get(SCOPE_NAME);
  }
}

package otel;

import io.opentelemetry.api.common.AttributeKey;
import io.opentelemetry.api.common.Attributes;
import io.opentelemetry.api.common.AttributesBuilder;
import java.util.Map;

public class AttributesUsage {
  // Establish static constant for attribute keys and reuse to avoid allocations
  private static final AttributeKey<String> SHOP_ID = AttributeKey.stringKey("com.acme.shop.id");
  private static final AttributeKey<String> SHOP_NAME =
      AttributeKey.stringKey("com.acme.shop.name");
  private static final AttributeKey<Long> CUSTOMER_ID =
      AttributeKey.longKey("com.acme.customer.id");
  private static final AttributeKey<String> CUSTOMER_NAME =
      AttributeKey.stringKey("com.acme.customer.name");

  public static void attributesUsage() {
    // Use a varargs initializer and pre-allocated attribute keys. This is the most efficient way to
    // create attributes.
    Attributes attributes =
        Attributes.of(
            SHOP_ID,
            "abc123",
            SHOP_NAME,
            "opentelemetry-demo",
            CUSTOMER_ID,
            123L,
            CUSTOMER_NAME,
            "Jack");

    // ...or use a builder.
    attributes =
        Attributes.builder()
            .put(SHOP_ID, "abc123")
            .put(SHOP_NAME, "opentelemetry-demo")
            .put(CUSTOMER_ID, 123)
            .put(CUSTOMER_NAME, "Jack")
            // Optionally initialize attribute keys on the fly
            .put(AttributeKey.stringKey("com.acme.string-key"), "value")
            .put(AttributeKey.booleanKey("com.acme.bool-key"), true)
            .put(AttributeKey.longKey("com.acme.long-key"), 1L)
            .put(AttributeKey.doubleKey("com.acme.double-key"), 1.1)
            .put(AttributeKey.stringArrayKey("com.acme.string-array-key"), "value1", "value2")
            .put(AttributeKey.booleanArrayKey("come.acme.bool-array-key"), true, false)
            .put(AttributeKey.longArrayKey("come.acme.long-array-key"), 1L, 2L)
            .put(AttributeKey.doubleArrayKey("come.acme.double-array-key"), 1.1, 2.2)
            // Optionally omit initializing AttributeKey
            .put("com.acme.string-key", "value")
            .put("com.acme.bool-key", true)
            .put("come.acme.long-key", 1L)
            .put("come.acme.double-key", 1.1)
            .put("come.acme.string-array-key", "value1", "value2")
            .put("come.acme.bool-array-key", true, false)
            .put("come.acme.long-array-key", 1L, 2L)
            .put("come.acme.double-array-key", 1.1, 2.2)
            .build();

    // Attributes has a variety of methods for manipulating and reading data.
    // Read an attribute key:
    String shopIdValue = attributes.get(SHOP_ID);
    // Inspect size:
    int size = attributes.size();
    boolean isEmpty = attributes.isEmpty();
    // Convert to a map representation:
    Map<AttributeKey<?>, Object> map = attributes.asMap();
    // Iterate through entries, printing each to the template: <key> (<type>): <value>\n
    attributes.forEach(
        (attributeKey, value) ->
            System.out.printf(
                "%s (%s): %s%n", attributeKey.getKey(), attributeKey.getType(), value));
    // Convert to a builder, remove the com.acme.customer.id and any entry whose key starts with
    // com.acme.shop, and build a new instance:
    AttributesBuilder builder = attributes.toBuilder();
    builder.remove(CUSTOMER_ID);
    builder.removeIf(attributeKey -> attributeKey.getKey().startsWith("com.acme.shop"));
    Attributes trimmedAttributes = builder.build();
  }
}

package otel;

import io.opentelemetry.api.OpenTelemetry;
import io.opentelemetry.api.common.Attributes;
import io.opentelemetry.api.logs.LoggerProvider;
import io.opentelemetry.api.metrics.MeterProvider;
import io.opentelemetry.api.trace.TracerProvider;
import io.opentelemetry.context.propagation.ContextPropagators;

public class OpenTelemetryUsage {
  private static final Attributes WIDGET_RED_CIRCLE = Util.WIDGET_RED_CIRCLE;

  public static void openTelemetryUsage(OpenTelemetry openTelemetry) {
    // Access TracerProvider, MeterProvider, LoggerProvider, ContextPropagators
    TracerProvider tracerProvider = openTelemetry.getTracerProvider();
    MeterProvider meterProvider = openTelemetry.getMeterProvider();
    LoggerProvider loggerProvider = openTelemetry.getLogsBridge();
    ContextPropagators propagators = openTelemetry.getPropagators();
  }
}

package otel;

import io.opentelemetry.api.GlobalOpenTelemetry;
import io.opentelemetry.api.OpenTelemetry;

public class GlobalOpenTelemetryNativeInstrumentationUsage {

  public static void globalOpenTelemetryUsage(OpenTelemetry openTelemetry) {
    // Initialized with OpenTelemetry from java agent if present, otherwise no-op implementation.
    MyClient client1 = new MyClientBuilder().build();

    // Initialized with an explicit OpenTelemetry instance, overriding the java agent instance.
    MyClient client2 = new MyClientBuilder().setOpenTelemetry(openTelemetry).build();
  }

  /**
   * An example library with native OpenTelemetry instrumentation, initialized via {@link
   * MyClientBuilder}.
   */
  public static class MyClient {
    private final OpenTelemetry openTelemetry;

    private MyClient(OpenTelemetry openTelemetry) {
      this.openTelemetry = openTelemetry;
    }

    // ... library methods omitted
  }

  /** Builder for {@link MyClient}. */
  public static class MyClientBuilder {
    // OpenTelemetry defaults to the GlobalOpenTelemetry instance if set, e.g. by the java agent or
    // by the application, else to a no-op implementation.
    private OpenTelemetry openTelemetry = GlobalOpenTelemetry.getOrNoop();

    /** Explicitly set the OpenTelemetry instance to use. */
    public MyClientBuilder setOpenTelemetry(OpenTelemetry openTelemetry) {
      this.openTelemetry = openTelemetry;
      return this;
    }

    /** Build the client. */
    public MyClient build() {
      return new MyClient(openTelemetry);
    }
  }
}

package otel;

import io.opentelemetry.api.GlobalOpenTelemetry;
import io.opentelemetry.api.OpenTelemetry;
import io.opentelemetry.sdk.autoconfigure.AutoConfiguredOpenTelemetrySdk;

public class GlobalOpenTelemetryManualInstrumentationUsage {

  public static void globalOpenTelemetryUsage() {
    // If GlobalOpenTelemetry is already set, e.g. by the java agent, use it.
    // Else, initialize an OpenTelemetry SDK instance and use it.
    OpenTelemetry openTelemetry =
        GlobalOpenTelemetry.isSet() ? GlobalOpenTelemetry.get() : initializeOpenTelemetry();

    // Install into manual instrumentation. This may involve setting as a singleton in the
    // application's dependency injection framework.
  }

  /** Initialize OpenTelemetry SDK using autoconfiguration. */
  public static OpenTelemetry initializeOpenTelemetry() {
    return AutoConfiguredOpenTelemetrySdk.initialize().getOpenTelemetrySdk();
  }
}

package otel;

import static io.opentelemetry.context.Context.current;

import io.opentelemetry.api.common.AttributeKey;
import io.opentelemetry.api.common.Attributes;
import io.opentelemetry.api.trace.Span;
import io.opentelemetry.api.trace.SpanContext;
import io.opentelemetry.api.trace.SpanKind;
import io.opentelemetry.api.trace.StatusCode;
import io.opentelemetry.api.trace.Tracer;
import java.util.Arrays;

public class SpanUsage {
  private static final Attributes WIDGET_RED_CIRCLE = Util.WIDGET_RED_CIRCLE;

  public static void spanUsage(Tracer tracer) {
    // Get a span builder by providing the span name
    Span span =
        tracer
            .spanBuilder("span name")
            // Set span kind
            .setSpanKind(SpanKind.INTERNAL)
            // Set attributes
            .setAttribute(AttributeKey.stringKey("com.acme.string-key"), "value")
            .setAttribute(AttributeKey.booleanKey("com.acme.bool-key"), true)
            .setAttribute(AttributeKey.longKey("com.acme.long-key"), 1L)
            .setAttribute(AttributeKey.doubleKey("com.acme.double-key"), 1.1)
            .setAttribute(
                AttributeKey.stringArrayKey("com.acme.string-array-key"),
                Arrays.asList("value1", "value2"))
            .setAttribute(
                AttributeKey.booleanArrayKey("come.acme.bool-array-key"),
                Arrays.asList(true, false))
            .setAttribute(
                AttributeKey.longArrayKey("come.acme.long-array-key"), Arrays.asList(1L, 2L))
            .setAttribute(
                AttributeKey.doubleArrayKey("come.acme.double-array-key"), Arrays.asList(1.1, 2.2))
            // Optionally omit initializing AttributeKey
            .setAttribute("com.acme.string-key", "value")
            .setAttribute("com.acme.bool-key", true)
            .setAttribute("come.acme.long-key", 1L)
            .setAttribute("come.acme.double-key", 1.1)
            .setAllAttributes(WIDGET_RED_CIRCLE)
            // Uncomment to optionally explicitly set the parent span context. If omitted, the
            // span's parent will be set using Context.current().
            // .setParent(parentContext)
            // Uncomment to optionally add links.
            // .addLink(linkContext, linkAttributes)
            // Start the span
            .startSpan();

    // Check if span is recording before computing additional data
    if (span.isRecording()) {
      // Update the span name with information not available when starting
      span.updateName("new span name");

      // Add additional attributes not available when starting
      span.setAttribute("com.acme.string-key2", "value");

      // Add additional span links not available when starting
      span.addLink(exampleLinkContext());
      // optionally include attributes on the link
      span.addLink(exampleLinkContext(), WIDGET_RED_CIRCLE);

      // Add span events
      span.addEvent("my-event");
      // optionally include attributes on the event
      span.addEvent("my-event", WIDGET_RED_CIRCLE);

      // Record exception, syntactic sugar for a span event with a specific shape
      span.recordException(new RuntimeException("error"));

      // Set the span status
      span.setStatus(StatusCode.OK, "status description");
    }

    // Finally, end the span
    span.end();
  }

  /** Return a dummy link context. */
  private static SpanContext exampleLinkContext() {
    return Span.fromContext(current()).getSpanContext();
  }
}

package otel;

import io.opentelemetry.api.trace.Span;
import io.opentelemetry.api.trace.Tracer;
import io.opentelemetry.context.Context;
import io.opentelemetry.context.Scope;

public class SpanAndContextUsage {
  private final Tracer tracer;

  SpanAndContextUsage(Tracer tracer) {
    this.tracer = tracer;
  }

  public void nestedSpanUsage() {
    // Start a span. Since we don't call makeCurrent(), we must explicitly call setParent on
    // children. Wrap code in try / finally to ensure we end the span.
    Span span = tracer.spanBuilder("span").startSpan();
    try {
      // Start a child span, explicitly setting the parent.
      Span childSpan =
          tracer
              .spanBuilder("span child")
              // Explicitly set parent.
              .setParent(span.storeInContext(Context.current()))
              .startSpan();
      // Call makeCurrent(), adding childSpan to Context.current(). Spans created inside the scope
      // will have their parent set to childSpan.
      try (Scope childSpanScope = childSpan.makeCurrent()) {
        // Call another method which creates a span. The span's parent will be childSpan since it is
        // started in the childSpan scope.
        doWork();
      } finally {
        childSpan.end();
      }
    } finally {
      span.end();
    }
  }

  private int doWork() {
    Span doWorkSpan = tracer.spanBuilder("doWork").startSpan();
    try (Scope scope = doWorkSpan.makeCurrent()) {
      int result = 0;
      for (int i = 0; i < 10; i++) {
        result += i;
      }
      return result;
    } finally {
      doWorkSpan.end();
    }
  }
}

package otel;

import static otel.Util.WIDGET_COLOR;
import static otel.Util.WIDGET_SHAPE;
import static otel.Util.computeWidgetColor;
import static otel.Util.computeWidgetShape;
import static otel.Util.customContext;

import io.opentelemetry.api.common.Attributes;
import io.opentelemetry.api.metrics.LongCounter;
import io.opentelemetry.api.metrics.Meter;

public class CounterUsage {
  private static final Attributes WIDGET_RED_CIRCLE = Util.WIDGET_RED_CIRCLE;

  public static void counterUsage(Meter meter) {
    // Construct a counter to record measurements that are always positive (monotonically
    // increasing).
    LongCounter counter =
        meter
            .counterBuilder("fully.qualified.counter")
            .setDescription("A count of produced widgets")
            .setUnit("{widget}")
            // optionally change the type to double
            // .ofDoubles()
            .build();

    // Record a measurement with no attributes or context.
    // Attributes defaults to Attributes.empty(), context to Context.current().
    counter.add(1L);

    // Record a measurement with attributes, using pre-allocated attributes whenever possible.
    counter.add(1L, WIDGET_RED_CIRCLE);
    // Sometimes, attributes must be computed using application context.
    counter.add(
        1L, Attributes.of(WIDGET_SHAPE, computeWidgetShape(), WIDGET_COLOR, computeWidgetColor()));

    // Record a measurement with attributes, and context.
    // Most users will opt to omit the context argument, preferring the default Context.current().
    counter.add(1L, WIDGET_RED_CIRCLE, customContext());
  }
}

package otel;

import static otel.Util.WIDGET_COLOR;
import static otel.Util.WIDGET_SHAPE;
import static otel.Util.computeWidgetColor;
import static otel.Util.computeWidgetShape;

import io.opentelemetry.api.common.Attributes;
import io.opentelemetry.api.metrics.Meter;
import io.opentelemetry.api.metrics.ObservableLongCounter;
import java.util.concurrent.atomic.AtomicLong;

public class AsyncCounterUsage {
  // Pre-allocate attributes whenever possible
  private static final Attributes WIDGET_RED_CIRCLE = Util.WIDGET_RED_CIRCLE;

  public static void asyncCounterUsage(Meter meter) {
    AtomicLong widgetCount = new AtomicLong();

    // Construct an async counter to observe an existing counter in a callback
    ObservableLongCounter asyncCounter =
        meter
            .counterBuilder("fully.qualified.counter")
            .setDescription("A count of produced widgets")
            .setUnit("{widget}")
            // Uncomment to optionally change the type to double
            // .ofDoubles()
            .buildWithCallback(
                // the callback is invoked when a MetricReader reads metrics
                observableMeasurement -> {
                  long currentWidgetCount = widgetCount.get();

                  // Record a measurement with no attributes.
                  // Attributes defaults to Attributes.empty().
                  observableMeasurement.record(currentWidgetCount);

                  // Record a measurement with attributes, using pre-allocated attributes whenever
                  // possible.
                  observableMeasurement.record(currentWidgetCount, WIDGET_RED_CIRCLE);
                  // Sometimes, attributes must be computed using application context.
                  observableMeasurement.record(
                      currentWidgetCount,
                      Attributes.of(
                          WIDGET_SHAPE, computeWidgetShape(), WIDGET_COLOR, computeWidgetColor()));
                });

    // Optionally close the counter to unregister the callback when required
    asyncCounter.close();
  }
}

package otel;

import static otel.Util.WIDGET_COLOR;
import static otel.Util.WIDGET_SHAPE;
import static otel.Util.computeWidgetColor;
import static otel.Util.computeWidgetShape;
import static otel.Util.customContext;

import io.opentelemetry.api.common.Attributes;
import io.opentelemetry.api.metrics.LongUpDownCounter;
import io.opentelemetry.api.metrics.Meter;

public class UpDownCounterUsage {

  private static final Attributes WIDGET_RED_CIRCLE = Util.WIDGET_RED_CIRCLE;

  public static void usage(Meter meter) {
    // Construct an updowncounter to record measurements that go up and down.
    LongUpDownCounter upDownCounter =
        meter
            .upDownCounterBuilder("fully.qualified.updowncounter")
            .setDescription("Current length of widget processing queue")
            .setUnit("{widget}")
            // Uncomment to optionally change the type to double
            // .ofDoubles()
            .build();

    // Record a measurement with no attributes or context.
    // Attributes defaults to Attributes.empty(), context to Context.current().
    upDownCounter.add(1L);

    // Record a measurement with attributes, using pre-allocated attributes whenever possible.
    upDownCounter.add(-1L, WIDGET_RED_CIRCLE);
    // Sometimes, attributes must be computed using application context.
    upDownCounter.add(
        -1L, Attributes.of(WIDGET_SHAPE, computeWidgetShape(), WIDGET_COLOR, computeWidgetColor()));

    // Record a measurement with attributes, and context.
    // Most users will opt to omit the context argument, preferring the default Context.current().
    upDownCounter.add(1L, WIDGET_RED_CIRCLE, customContext());
  }
}

package otel;

import static otel.Util.WIDGET_COLOR;
import static otel.Util.WIDGET_SHAPE;
import static otel.Util.computeWidgetColor;
import static otel.Util.computeWidgetShape;

import io.opentelemetry.api.common.Attributes;
import io.opentelemetry.api.metrics.Meter;
import io.opentelemetry.api.metrics.ObservableLongUpDownCounter;
import java.util.concurrent.atomic.AtomicLong;

public class AsyncUpDownCounterUsage {
  private static final Attributes WIDGET_RED_CIRCLE = Util.WIDGET_RED_CIRCLE;

  public static void asyncUpDownCounterUsage(Meter meter) {
    AtomicLong queueLength = new AtomicLong();

    // Construct an async updowncounter to observe an existing up down counter in a callback
    ObservableLongUpDownCounter asyncUpDownCounter =
        meter
            .upDownCounterBuilder("fully.qualified.updowncounter")
            .setDescription("Current length of widget processing queue")
            .setUnit("{widget}")
            // Uncomment to optionally change the type to double
            // .ofDoubles()
            .buildWithCallback(
                // the callback is invoked when a MetricReader reads metrics
                observableMeasurement -> {
                  long currentWidgetCount = queueLength.get();

                  // Record a measurement with no attributes.
                  // Attributes defaults to Attributes.empty().
                  observableMeasurement.record(currentWidgetCount);

                  // Record a measurement with attributes, using pre-allocated attributes whenever
                  // possible.
                  observableMeasurement.record(currentWidgetCount, WIDGET_RED_CIRCLE);
                  // Sometimes, attributes must be computed using application context.
                  observableMeasurement.record(
                      currentWidgetCount,
                      Attributes.of(
                          WIDGET_SHAPE, computeWidgetShape(), WIDGET_COLOR, computeWidgetColor()));
                });

    // Optionally close the counter to unregister the callback when required
    asyncUpDownCounter.close();
  }
}

package otel;

import static otel.Util.WIDGET_COLOR;
import static otel.Util.WIDGET_SHAPE;
import static otel.Util.computeWidgetColor;
import static otel.Util.computeWidgetShape;
import static otel.Util.customContext;

import io.opentelemetry.api.common.Attributes;
import io.opentelemetry.api.metrics.DoubleHistogram;
import io.opentelemetry.api.metrics.Meter;

public class HistogramUsage {
  private static final Attributes WIDGET_RED_CIRCLE = Util.WIDGET_RED_CIRCLE;

  public static void histogramUsage(Meter meter) {
    // Construct a histogram to record measurements where the distribution is important.
    DoubleHistogram histogram =
        meter
            .histogramBuilder("fully.qualified.histogram")
            .setDescription("Length of time to process a widget")
            .setUnit("s")
            // Uncomment to optionally provide advice on useful default explicit bucket boundaries
            // .setExplicitBucketBoundariesAdvice(Arrays.asList(1.0, 2.0, 3.0))
            // Uncomment to optionally change the type to long
            // .ofLongs()
            .build();

    // Record a measurement with no attributes or context.
    // Attributes defaults to Attributes.empty(), context to Context.current().
    histogram.record(1.1);

    // Record a measurement with attributes, using pre-allocated attributes whenever possible.
    histogram.record(2.2, WIDGET_RED_CIRCLE);
    // Sometimes, attributes must be computed using application context.
    histogram.record(
        3.2, Attributes.of(WIDGET_SHAPE, computeWidgetShape(), WIDGET_COLOR, computeWidgetColor()));

    // Record a measurement with attributes, and context.
    // Most users will opt to omit the context argument, preferring the default Context.current().
    histogram.record(4.4, WIDGET_RED_CIRCLE, customContext());
  }
}

package otel;

import static otel.Util.WIDGET_COLOR;
import static otel.Util.WIDGET_SHAPE;
import static otel.Util.computeWidgetColor;
import static otel.Util.computeWidgetShape;
import static otel.Util.customContext;

import io.opentelemetry.api.common.Attributes;
import io.opentelemetry.api.metrics.DoubleGauge;
import io.opentelemetry.api.metrics.Meter;

public class GaugeUsage {
  private static final Attributes WIDGET_RED_CIRCLE = Util.WIDGET_RED_CIRCLE;

  public static void gaugeUsage(Meter meter) {
    // Construct a gauge to record measurements as they occur, which cannot be spatially
    // re-aggregated.
    DoubleGauge gauge =
        meter
            .gaugeBuilder("fully.qualified.gauge")
            .setDescription("The current temperature of the widget processing line")
            .setUnit("K")
            // Uncomment to optionally change the type to long
            // .ofLongs()
            .build();

    // Record a measurement with no attributes or context.
    // Attributes defaults to Attributes.empty(), context to Context.current().
    gauge.set(273.0);

    // Record a measurement with attributes, using pre-allocated attributes whenever possible.
    gauge.set(273.0, WIDGET_RED_CIRCLE);
    // Sometimes, attributes must be computed using application context.
    gauge.set(
        273.0,
        Attributes.of(WIDGET_SHAPE, computeWidgetShape(), WIDGET_COLOR, computeWidgetColor()));

    // Record a measurement with attributes, and context.
    // Most users will opt to omit the context argument, preferring the default Context.current().
    gauge.set(1L, WIDGET_RED_CIRCLE, customContext());
  }
}

package otel;

import static otel.Util.WIDGET_COLOR;
import static otel.Util.WIDGET_SHAPE;
import static otel.Util.computeWidgetColor;
import static otel.Util.computeWidgetShape;

import io.opentelemetry.api.common.Attributes;
import io.opentelemetry.api.metrics.Meter;
import io.opentelemetry.api.metrics.ObservableDoubleGauge;
import java.util.concurrent.atomic.AtomicReference;

public class AsyncGaugeUsage {
  private static final Attributes WIDGET_RED_CIRCLE = Util.WIDGET_RED_CIRCLE;

  public static void asyncGaugeUsage(Meter meter) {
    AtomicReference<Double> processingLineTemp = new AtomicReference<>(273.0);

    // Construct an async gauge to observe an existing gauge in a callback
    ObservableDoubleGauge asyncGauge =
        meter
            .gaugeBuilder("fully.qualified.gauge")
            .setDescription("The current temperature of the widget processing line")
            .setUnit("K")
            // Uncomment to optionally change the type to long
            // .ofLongs()
            .buildWithCallback(
                // the callback is invoked when a MetricReader reads metrics
                observableMeasurement -> {
                  double currentWidgetCount = processingLineTemp.get();

                  // Record a measurement with no attributes.
                  // Attributes defaults to Attributes.empty().
                  observableMeasurement.record(currentWidgetCount);

                  // Record a measurement with attributes, using pre-allocated attributes whenever
                  // possible.
                  observableMeasurement.record(currentWidgetCount, WIDGET_RED_CIRCLE);
                  // Sometimes, attributes must be computed using application context.
                  observableMeasurement.record(
                      currentWidgetCount,
                      Attributes.of(
                          WIDGET_SHAPE, computeWidgetShape(), WIDGET_COLOR, computeWidgetColor()));
                });

    // Optionally close the gauge to unregister the callback when required
    asyncGauge.close();
  }
}

package otel;

import io.opentelemetry.api.common.AttributeKey;
import io.opentelemetry.api.common.Attributes;
import io.opentelemetry.api.common.Value;
import io.opentelemetry.api.logs.Logger;
import io.opentelemetry.api.logs.Severity;
import java.util.Arrays;
import java.util.Map;
import java.util.concurrent.TimeUnit;

public class LogRecordUsage {
  private static final Attributes WIDGET_RED_CIRCLE = Util.WIDGET_RED_CIRCLE;

  public static void logRecordUsage(Logger logger) {
    logger
        .logRecordBuilder()
        // Set body. Note, setBody(..) is called multiple times for demonstration purposes but only
        // the last call is used.
        // Set the body to a string, syntactic sugar for setBody(Value.of("log message"))
        .setBody("log message")
        // Optionally set the body to a Value to record arbitrarily complex structured data
        .setBody(Value.of("log message"))
        .setBody(Value.of(1L))
        .setBody(Value.of(1.1))
        .setBody(Value.of(true))
        .setBody(Value.of(new byte[] {'a', 'b', 'c'}))
        .setBody(Value.of(Value.of("entry1"), Value.of("entry2")))
        .setBody(
            Value.of(
                Map.of(
                    "stringKey",
                    Value.of("entry1"),
                    "mapKey",
                    Value.of(Map.of("stringKey", Value.of("entry2"))))))
        // Set severity
        .setSeverity(Severity.DEBUG)
        .setSeverityText("debug")
        // Set timestamp
        .setTimestamp(System.currentTimeMillis(), TimeUnit.MILLISECONDS)
        // Optionally set the timestamp when the log was observed
        .setObservedTimestamp(System.currentTimeMillis(), TimeUnit.MILLISECONDS)
        // Set attributes
        .setAttribute(AttributeKey.stringKey("com.acme.string-key"), "value")
        .setAttribute(AttributeKey.booleanKey("com.acme.bool-key"), true)
        .setAttribute(AttributeKey.longKey("com.acme.long-key"), 1L)
        .setAttribute(AttributeKey.doubleKey("com.acme.double-key"), 1.1)
        .setAttribute(
            AttributeKey.stringArrayKey("com.acme.string-array-key"),
            Arrays.asList("value1", "value2"))
        .setAttribute(
            AttributeKey.booleanArrayKey("come.acme.bool-array-key"), Arrays.asList(true, false))
        .setAttribute(AttributeKey.longArrayKey("come.acme.long-array-key"), Arrays.asList(1L, 2L))
        .setAttribute(
            AttributeKey.doubleArrayKey("come.acme.double-array-key"), Arrays.asList(1.1, 2.2))
        .setAllAttributes(WIDGET_RED_CIRCLE)
        // Uncomment to optionally explicitly set the context used to correlate with spans. If
        // omitted, Context.current() is used.
        // .setContext(context)
        // Emit the log record
        .emit();
  }
}