content: /*
   * Copyright The OpenTelemetry Authors
   * SPDX-License-Identifier: Apache-2.0
   */
  
  package io.opentelemetry.instrumentation.runtimemetrics.java17.internal.memory;
  
  import io.opentelemetry.api.common.Attributes;
  import io.opentelemetry.api.metrics.Meter;
  import io.opentelemetry.instrumentation.runtimemetrics.java17.JfrFeature;
  import io.opentelemetry.instrumentation.runtimemetrics.java17.internal.Constants;
  import io.opentelemetry.instrumentation.runtimemetrics.java17.internal.RecordedEventHandler;
  import java.util.ArrayList;
  import java.util.List;
  import java.util.logging.Logger;
  import jdk.jfr.consumer.RecordedEvent;
  
  /**
   * This class handles G1HeapSummary JFR events. For GC purposes they come in pairs. Basic heap
   * values are sourced from GCHeapSummary - this is young generational details This class is internal
   * and is hence not for public use. Its APIs are unstable and can change at any time.
   */
  public final class G1HeapSummaryHandler implements RecordedEventHandler {
    private static final Logger logger = Logger.getLogger(G1HeapSummaryHandler.class.getName());
  
    private static final String EVENT_NAME = "jdk.G1HeapSummary";
    private static final String BEFORE = "Before GC";
    private static final String AFTER = "After GC";
    private static final String GC_ID = "gcId";
    private static final String EDEN_USED_SIZE = "edenUsedSize";
    private static final String EDEN_TOTAL_SIZE = "edenTotalSize";
    private static final String SURVIVOR_USED_SIZE = "survivorUsedSize";
    private static final String WHEN = "when";
    private static final Attributes ATTR_MEMORY_EDEN =
        Attributes.of(
            Constants.ATTR_MEMORY_TYPE, Constants.HEAP, Constants.ATTR_MEMORY_POOL, "G1 Eden Space");
    private static final Attributes ATTR_MEMORY_SURVIVOR =
        Attributes.of(
            Constants.ATTR_MEMORY_TYPE,
            Constants.HEAP,
            Constants.ATTR_MEMORY_POOL,
            "G1 Survivor Space");
    //  private static final Attributes ATTR_MEMORY_OLD_USED =
    //      Attributes.of(ATTR_TYPE, HEAP, ATTR_POOL, "G1 Old Gen"); // TODO needs jdk JFR support
  
    private final List<AutoCloseable> observables = new ArrayList<>();
  
    private volatile long usageEden = 0;
    private volatile long usageEdenAfter = 0;
    private volatile long usageSurvivor = 0;
    private volatile long usageSurvivorAfter = 0;
    private volatile long committedEden = 0;
  
    public G1HeapSummaryHandler(Meter meter) {
      observables.add(
          meter
              .upDownCounterBuilder(Constants.METRIC_NAME_MEMORY)
              .setDescription(Constants.METRIC_DESCRIPTION_MEMORY)
              .setUnit(Constants.BYTES)
              .buildWithCallback(
                  measurement -> {
                    measurement.record(usageEden, ATTR_MEMORY_EDEN);
                    measurement.record(usageSurvivor, ATTR_MEMORY_SURVIVOR);
                  }));
      observables.add(
          meter
              .upDownCounterBuilder(Constants.METRIC_NAME_MEMORY_AFTER)
              .setDescription(Constants.METRIC_DESCRIPTION_MEMORY_AFTER)
              .setUnit(Constants.BYTES)
              .buildWithCallback(
                  measurement -> {
                    measurement.record(usageEdenAfter, ATTR_MEMORY_EDEN);
                    measurement.record(usageSurvivorAfter, ATTR_MEMORY_SURVIVOR);
                  }));
      observables.add(
          meter
              .upDownCounterBuilder(Constants.METRIC_NAME_COMMITTED)
              .setDescription(Constants.METRIC_DESCRIPTION_COMMITTED)
              .setUnit(Constants.BYTES)
              .buildWithCallback(measurement -> measurement.record(committedEden, ATTR_MEMORY_EDEN)));
    }
  
    @Override
    public String getEventName() {
      return EVENT_NAME;
    }
  
    @Override
    public JfrFeature getFeature() {
      return JfrFeature.MEMORY_POOL_METRICS;
    }
  
    @Override
    public void accept(RecordedEvent ev) {
      String when;
      if (ev.hasField(WHEN)) {
        when = ev.getString(WHEN);
      } else {
        logger.fine(String.format("G1 GC Event seen without when: %s", ev));
        return;
      }
      if (!(BEFORE.equals(when) || AFTER.equals(when))) {
        logger.fine(String.format("G1 GC Event seen where when is neither before nor after: %s", ev));
        return;
      }
  
      if (!ev.hasField(GC_ID)) {
        logger.fine(String.format("G1 GC Event seen without GC ID: %s", ev));
        return;
      }
      recordValues(ev, BEFORE.equals(when));
    }
  
    private void recordValues(RecordedEvent event, boolean before) {
      if (event.hasField(EDEN_USED_SIZE)) {
        if (before) {
          usageEden = event.getLong(EDEN_USED_SIZE);
        } else {
          usageEdenAfter = event.getLong(EDEN_USED_SIZE);
        }
      }
  
      if (event.hasField(SURVIVOR_USED_SIZE)) {
        if (before) {
          usageSurvivor = event.getLong(SURVIVOR_USED_SIZE);
        } else {
          usageSurvivorAfter = event.getLong(SURVIVOR_USED_SIZE);
        }
      }
  
      if (event.hasField(EDEN_TOTAL_SIZE)) {
        committedEden = event.getLong(EDEN_TOTAL_SIZE);
      }
    }
  
    @Override
    public void close() {
      RecordedEventHandler.closeObservables(observables);
    }
  }
  