content: /*
   * Licensed to the Apache Software Foundation (ASF) under one or more
   * contributor license agreements. See the NOTICE file distributed with this
   * work for additional information regarding copyright ownership. The ASF
   * licenses this file to you under the Apache License, Version 2.0 (the
   * "License"); you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   * http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
   * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
   * License for the specific language governing permissions and limitations under
   * the License.
   */
  package org.apache.bookkeeper.stats.otel;
  
  // CHECKSTYLE.OFF: IllegalImport
  import io.netty.util.internal.PlatformDependent;
  import io.opentelemetry.api.OpenTelemetry;
  import io.opentelemetry.api.common.Attributes;
  import io.opentelemetry.api.metrics.Meter;
  import io.opentelemetry.instrumentation.runtimemetrics.java8.BufferPools;
  import io.opentelemetry.instrumentation.runtimemetrics.java8.Classes;
  import io.opentelemetry.instrumentation.runtimemetrics.java8.Cpu;
  import io.opentelemetry.instrumentation.runtimemetrics.java8.GarbageCollector;
  import io.opentelemetry.instrumentation.runtimemetrics.java8.MemoryPools;
  import io.opentelemetry.instrumentation.runtimemetrics.java8.Threads;
  import io.opentelemetry.sdk.autoconfigure.AutoConfiguredOpenTelemetrySdk;
  import io.opentelemetry.sdk.metrics.Aggregation;
  import io.opentelemetry.sdk.metrics.InstrumentSelector;
  import io.opentelemetry.sdk.metrics.InstrumentType;
  import io.opentelemetry.sdk.metrics.View;
  import java.lang.management.BufferPoolMXBean;
  import java.lang.management.ManagementFactory;
  import java.lang.reflect.Field;
  import java.util.Arrays;
  import java.util.List;
  import java.util.Optional;
  import java.util.concurrent.ConcurrentHashMap;
  import java.util.concurrent.ConcurrentMap;
  import java.util.concurrent.atomic.AtomicLong;
  import java.util.function.Supplier;
  import lombok.extern.slf4j.Slf4j;
  import org.apache.bookkeeper.stats.StatsLogger;
  import org.apache.bookkeeper.stats.StatsProvider;
  import org.apache.commons.configuration2.Configuration;
  // CHECKSTYLE.ON: IllegalImport
  
  @Slf4j
  public class OtelMetricsProvider implements StatsProvider {
  
      private static final String METER_NAME = "org.apache.bookkeeper";
  
      /*
       * These acts a registry of the metrics defined in this provider
       */
      final ConcurrentMap<ScopeContext, OtelCounter> counters = new ConcurrentHashMap<>();
      final ConcurrentMap<ScopeContext, OtelOpStatsLogger> opStats = new ConcurrentHashMap<>();
  
      private static final List<Double> histogramBuckets = Arrays.asList(
              0.1, 0.2, 0.5,
              1.0, 2.0, 5.0,
              10.0, 20.0, 50.0,
              100.0, 200.0, 500.0,
              1_000.0, 2_000.0, 5_000.0,
              10_000.0, 20_000.0, 50_000.0
      );
  
      private final OpenTelemetry openTelemetry;
  
      final Meter meter;
  
      OtelMetricsProvider() {
          AutoConfiguredOpenTelemetrySdk sdk = AutoConfiguredOpenTelemetrySdk.builder()
                  .addMeterProviderCustomizer(
                          (sdkMeterProviderBuilder, configProperties) ->
                                  sdkMeterProviderBuilder.registerView(
                                          InstrumentSelector.builder()
                                                  .setMeterName(METER_NAME)
                                                  .setType(InstrumentType.HISTOGRAM)
                                                  .build(),
                                          View.builder()
                                                  .setAggregation(Aggregation.explicitBucketHistogram(histogramBuckets))
                                                  .build())
  
                  ).build();
          this.openTelemetry = sdk.getOpenTelemetrySdk();
          this.meter = openTelemetry.getMeter(METER_NAME);
      }
  
      @Override
      public void start(Configuration conf) {
          boolean exposeDefaultJVMMetrics = conf.getBoolean("exposeDefaultJVMMetrics", true);
          if (exposeDefaultJVMMetrics) {
              // Include standard JVM stats
              MemoryPools.registerObservers(openTelemetry);
              BufferPools.registerObservers(openTelemetry);
              Classes.registerObservers(openTelemetry);
              Cpu.registerObservers(openTelemetry);
              Threads.registerObservers(openTelemetry);
              GarbageCollector.registerObservers(openTelemetry);
  
              meter.gaugeBuilder("process.runtime.jvm.memory.direct_bytes_used")
                      .buildWithCallback(odm -> odm.record(getDirectMemoryUsage.get()));
  
              meter.gaugeBuilder("process.runtime.jvm.memory.direct_bytes_max")
                      .buildWithCallback(odm -> odm.record(PlatformDependent.estimateMaxDirectMemory()));
          }
      }
  
      @Override
      public void stop() {
      }
  
      @Override
      public StatsLogger getStatsLogger(String scope) {
          return new OtelStatsLogger(this, scope, Attributes.empty());
      }
  
      /*
       * Try to get Netty counter of used direct memory. This will be correct, unlike the JVM values.
       */
      private static final AtomicLong directMemoryUsage;
      private static final Optional<BufferPoolMXBean> poolMxBeanOp;
      private static final Supplier<Double> getDirectMemoryUsage;
  
      static {
          if (PlatformDependent.useDirectBufferNoCleaner()) {
              poolMxBeanOp = Optional.empty();
              AtomicLong tmpDirectMemoryUsage = null;
              try {
                  Field field = PlatformDependent.class.getDeclaredField("DIRECT_MEMORY_COUNTER");
                  field.setAccessible(true);
                  tmpDirectMemoryUsage = (AtomicLong) field.get(null);
              } catch (Throwable t) {
                  log.warn("Failed to access netty DIRECT_MEMORY_COUNTER field {}", t.getMessage());
              }
              directMemoryUsage = tmpDirectMemoryUsage;
              getDirectMemoryUsage = () -> directMemoryUsage != null ? directMemoryUsage.get() : Double.NaN;
          } else {
              directMemoryUsage = null;
              List<BufferPoolMXBean> platformMXBeans = ManagementFactory.getPlatformMXBeans(BufferPoolMXBean.class);
              poolMxBeanOp = platformMXBeans.stream()
                      .filter(bufferPoolMXBean -> bufferPoolMXBean.getName().equals("direct")).findAny();
              getDirectMemoryUsage = () -> poolMxBeanOp.isPresent() ? poolMxBeanOp.get().getMemoryUsed() : Double.NaN;
          }
      }
  }
  