import io.opencensus.common.Scope;
import io.opencensus.trace.Tracer;
import io.opencensus.trace.Tracing;
import io.opencensus.trace.samplers.Samplers;

public final class MyClassWithTracing {
  private static final Tracer tracer = Tracing.getTracer();

  public static void doWork() {
    // Create a child Span of the current Span. Always record events for this span and force it to
    // be sampled. This makes it easier to try out the example, but unless you have a clear use
    // case, you don't need to explicitly set record events or sampler.
    try (Scope ss =
        tracer
            .spanBuilder("MyChildWorkSpan")
            .setRecordEvents(true)
            .setSampler(Samplers.alwaysSample())
            .startScopedSpan()) {
      doInitialWork();
      tracer.getCurrentSpan().addAnnotation("Finished initial work");
      doFinalWork();
    }
  }

  private static void doInitialWork() {
    // ...
    tracer.getCurrentSpan().addAnnotation("Important.");
    // ...
  }

  private static void doFinalWork() {
    // ...
    tracer.getCurrentSpan().addAnnotation("More important.");
    // ...
  }
}

import io.opencensus.common.Scope;
import io.opencensus.stats.Aggregation;
import io.opencensus.stats.BucketBoundaries;
import io.opencensus.stats.Measure.MeasureLong;
import io.opencensus.stats.Stats;
import io.opencensus.stats.StatsRecorder;
import io.opencensus.stats.View;
import io.opencensus.stats.ViewData;
import io.opencensus.stats.ViewManager;
import io.opencensus.tags.TagKey;
import io.opencensus.tags.TagValue;
import io.opencensus.tags.Tagger;
import io.opencensus.tags.Tags;
import java.util.Arrays;
import java.util.Collections;

public final class MyClassWithStats {
  private static final Tagger tagger = Tags.getTagger();
  private static final ViewManager viewManager = Stats.getViewManager();
  private static final StatsRecorder statsRecorder = Stats.getStatsRecorder();

  // frontendKey allows us to break down the recorded data
  private static final TagKey FRONTEND_KEY = TagKey.create("myorg_keys_frontend");

  // videoSize will measure the size of processed videos.
  private static final MeasureLong VIDEO_SIZE =
      MeasureLong.create("my.org/measure/video_size", "size of processed videos", "By");

  // Create view to see the processed video size distribution broken down by frontend.
  // The view has bucket boundaries (0, 256, 65536) that will group measure values into
  // histogram buckets.
  private static final View.Name VIDEO_SIZE_VIEW_NAME = View.Name.create("my.org/views/video_size");
  private static final View VIDEO_SIZE_VIEW =
      View.create(
          VIDEO_SIZE_VIEW_NAME,
          "processed video size over time",
          VIDEO_SIZE,
          Aggregation.Distribution.create(
              BucketBoundaries.create(Arrays.asList(0.0, 256.0, 65536.0))),
          Collections.singletonList(FRONTEND_KEY));

  public static void initialize() {
    // ...
    viewManager.registerView(VIDEO_SIZE_VIEW);
  }

  public static void processVideo() {
    try (Scope scopedTags =
        tagger
            .currentBuilder()
            .put(FRONTEND_KEY, TagValue.create("mobile-ios9.3.5"))
            .buildScoped()) {
      // Processing video.
      // ...

      // Record the processed video size.
      statsRecorder.newMeasureMap().put(VIDEO_SIZE, 25648).record();
    }
  }

  public static void printStats() {
    ViewData viewData = viewManager.getView(VIDEO_SIZE_VIEW_NAME);
    System.out.println(
        String.format("Recorded stats for %s:\n %s", VIDEO_SIZE_VIEW_NAME.asString(), viewData));
  }
}