/*
 * 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.geode;


import java.util.function.DoubleSupplier;
import java.util.function.IntSupplier;
import java.util.function.LongSupplier;

/**
 * Instances of this interface maintain the values of various application-defined statistics. The
 * statistics themselves are described by an instance of {@link StatisticsType}.
 *
 * <P>
 * To get an instance of this interface use an instance of {@link StatisticsFactory}.
 * <P>
 *
 * For improved performance, each statistic may be referred to by its {@link #nameToDescriptor
 * descriptor}.
 * <P>
 * For optimal performance, each statistic may be referred to by its {@link #nameToId id} in the
 * statistics object. Note that ids can not be mapped back to their name and methods that take ids
 * are unsafe. It is important to call the correct type of method for the given id. For example if
 * your stat is a long then incLong must be called instead of incDouble.
 * <p>
 * Note that as of the 5.1 release the <code>incLong</code>, and
 * <code>incDouble</code> methods no longer return the new value of the statistic. They now return
 * <code>void</code>. This incompatible change was made to allow for a more efficient concurrent
 * increment implementation.
 * <P>
 *
 * @see <A href="package-summary.html#statistics">Package introduction</A>
 *
 *
 * @since GemFire 3.0
 *
 */
public interface Statistics {

  /**
   * Closes these statistics. After statistics have been closed, they are no longer archived. A
   * value access on a closed statistics always results in zero. A value modification on a closed
   * statistics is ignored.
   */
  void close();

  //////////////////////// accessor Methods ///////////////////////

  /**
   * Returns the id of the statistic with the given name in this statistics instance.
   *
   * @param name the name of the statistic
   * @return the id of the statistic
   * @throws IllegalArgumentException No statistic named <code>name</code> exists in this statistics
   *         instance.
   *
   * @see StatisticsType#nameToId
   */
  int nameToId(String name);


  /**
   * Returns the descriptor of the statistic with the given name in this statistics instance.
   *
   * @param name the name of the statistic
   * @return the {@link StatisticDescriptor descriptor} of the statistic
   * @throws IllegalArgumentException No statistic named <code>name</code> exists in this statistics
   *         instance.
   *
   * @see StatisticsType#nameToDescriptor
   */
  StatisticDescriptor nameToDescriptor(String name);

  /**
   * Gets a value that uniquely identifies this statistics.
   *
   * @return a value that uniquely identifies this statistics
   */
  long getUniqueId();

  /**
   * Gets the {@link StatisticsType} of this instance.
   *
   * @return the {@link StatisticsType} of this instance
   */
  StatisticsType getType();

  /**
   * Gets the text associated with this instance that helps identify it.
   *
   * @return the text associated with this instance that helps identify it
   */
  String getTextId();

  /**
   * Gets the number associated with this instance that helps identify it.
   *
   * @return the number associated with this instance that helps identify it
   */
  long getNumericId();

  /**
   * Returns true if modifications are atomic. This means that multiple threads, can safely modify
   * this instance without extra synchronization.
   * <p>
   * Returns false if modifications are not atomic. This means that modifications to this instance
   * are cheaper but not thread safe.
   *
   * @return whether modifications are atomic
   */
  boolean isAtomic();

  /**
   * Returns true if the instance has been {@link #close closed}.
   *
   * @return whether the instance has been {@link #close closed}.
   */
  boolean isClosed();

  //////////////////////// set() Methods ///////////////////////

  /**
   * Sets the value of a statistic with the given <code>id</code> whose type is <code>int</code>.
   *
   * @param id a statistic id obtained with {@link #nameToId} or {@link StatisticsType#nameToId}.
   * @param value the value to set the statistic to
   *
   * @throws ArrayIndexOutOfBoundsException If the id is invalid.
   * @deprecated as of Geode 1.10, use {@link #setLong(int, long)} instead
   */
  @Deprecated
  void setInt(int id, int value);

  /**
   * Sets the value of a named statistic of type <code>int</code>
   *
   * @param name the name of the statistic
   * @param value the value to set the statistic to
   * @throws IllegalArgumentException If no statistic exists named <code>name</code> or if the
   *         statistic with name <code>name</code> is not of type <code>int</code>.
   * @deprecated as of Geode 1.10, use {@link #setLong(String, long)} instead
   */
  @Deprecated
  void setInt(String name, int value);

  /**
   * Sets the value of a described statistic of type <code>int</code>
   *
   * @param descriptor a statistic descriptor obtained with {@link #nameToDescriptor} or
   *        {@link StatisticsType#nameToDescriptor}.
   * @param value the value to set the statistic to
   * @throws IllegalArgumentException If no statistic exists for the given <code>descriptor</code>
   *         or if the described statistic is not of type <code>int</code>.
   * @deprecated as of Geode 1.10, use {@link #setLong(StatisticDescriptor, long)} instead
   */
  @Deprecated
  void setInt(StatisticDescriptor descriptor, int value);

  /**
   * Sets the value of a statistic with the given <code>id</code> whose type is <code>long</code>.
   *
   * @param id a statistic id obtained with {@link #nameToId} or {@link StatisticsType#nameToId}.
   * @param value the value to set the statistic to
   *
   * @throws ArrayIndexOutOfBoundsException If the id is invalid.
   */
  void setLong(int id, long value);

  /**
   * Sets the value of a described statistic of type <code>long</code>
   *
   * @param descriptor a statistic descriptor obtained with {@link #nameToDescriptor} or
   *        {@link StatisticsType#nameToDescriptor}.
   * @param value the value to set the statistic to
   * @throws IllegalArgumentException If no statistic exists for the given <code>descriptor</code>
   *         or if the described statistic is not of type <code>long</code>.
   */
  void setLong(StatisticDescriptor descriptor, long value);

  /**
   * Sets the value of a named statistic of type <code>long</code>.
   *
   * @param name the name of the statistic
   * @param value the value to set the statistic to
   * @throws IllegalArgumentException If no statistic exists named <code>name</code> or if the
   *         statistic with name <code>name</code> is not of type <code>long</code>.
   */
  void setLong(String name, long value);

  /**
   * Sets the value of a statistic with the given <code>id</code> whose type is <code>double</code>.
   *
   * @param id a statistic id obtained with {@link #nameToId} or {@link StatisticsType#nameToId}.
   * @param value the value to set the statistic to
   *
   * @throws ArrayIndexOutOfBoundsException If the id is invalid.
   */
  void setDouble(int id, double value);

  /**
   * Sets the value of a described statistic of type <code>double</code>
   *
   * @param descriptor a statistic descriptor obtained with {@link #nameToDescriptor} or
   *        {@link StatisticsType#nameToDescriptor}.
   * @param value the value to set the statistic to
   * @throws IllegalArgumentException If no statistic exists for the given <code>descriptor</code>
   *         or if the described statistic is not of type <code>double</code>.
   */
  void setDouble(StatisticDescriptor descriptor, double value);

  /**
   * Sets the value of a named statistic of type <code>double</code>.
   *
   * @param name the name of the statistic
   * @param value the value to set the statistic to
   * @throws IllegalArgumentException If no statistic exists named <code>name</code> or if the
   *         statistic with name <code>name</code> is not of type <code>double</code>.
   */
  void setDouble(String name, double value);

  /////////////////////// get() Methods ///////////////////////

  /**
   * Returns the value of the identified statistic of type <code>int</code>.
   *
   * @param id a statistic id obtained with {@link #nameToId} or {@link StatisticsType#nameToId}.
   * @return the value of the statistic
   * @throws ArrayIndexOutOfBoundsException If the id is invalid.
   * @deprecated as of Geode 1.10, use {@link #getLong(int)} instead
   */
  @Deprecated
  int getInt(int id);

  /**
   * Returns the value of the described statistic of type <code>int</code>.
   *
   * @param descriptor a statistic descriptor obtained with {@link #nameToDescriptor} or
   *        {@link StatisticsType#nameToDescriptor}.
   * @return the value of the statistic
   * @throws IllegalArgumentException If no statistic exists with the specified
   *         <code>descriptor</code> or if the described statistic is not of type <code>int</code>.
   * @deprecated as of Geode 1.10, use {@link #getLong(StatisticDescriptor)} instead
   */
  @Deprecated
  int getInt(StatisticDescriptor descriptor);

  /**
   * Returns the value of the statistic of type <code>int</code> at the given name.
   *
   * @param name the name of the statistic
   * @return the value of the statistic
   * @throws IllegalArgumentException If no statistic exists with name <code>name</code> or if the
   *         statistic named <code>name</code> is not of type <code>int</code>.
   * @deprecated as of Geode 1.10, use {@link #getLong(String)} instead
   */
  @Deprecated
  int getInt(String name);

  /**
   * Returns the value of the identified statistic of type <code>long</code>.
   *
   * @param id a statistic id obtained with {@link #nameToId} or {@link StatisticsType#nameToId}.
   * @return the value of the statistic
   * @throws ArrayIndexOutOfBoundsException If the id is invalid.
   */
  long getLong(int id);


  /**
   * Returns the value of the described statistic of type <code>long</code>.
   *
   * @param descriptor a statistic descriptor obtained with {@link #nameToDescriptor} or
   *        {@link StatisticsType#nameToDescriptor}.
   * @return the value of the statistic
   * @throws IllegalArgumentException If no statistic exists with the specified
   *         <code>descriptor</code> or if the described statistic is not of type <code>long</code>.
   */
  long getLong(StatisticDescriptor descriptor);

  /**
   * Returns the value of the statistic of type <code>long</code> at the given name.
   *
   * @param name the name of the statistic
   * @return the value of the statistic
   * @throws IllegalArgumentException If no statistic exists with name <code>name</code> or if the
   *         statistic named <code>name</code> is not of type <code>long</code>.
   */
  long getLong(String name);

  /**
   * Returns the value of the identified statistic of type <code>double</code>.
   *
   * @param id a statistic id obtained with {@link #nameToId} or {@link StatisticsType#nameToId}.
   * @return the value of the statistic
   * @throws ArrayIndexOutOfBoundsException If the id is invalid.
   */
  double getDouble(int id);

  /**
   * Returns the value of the described statistic of type <code>double</code>.
   *
   * @param descriptor a statistic descriptor obtained with {@link #nameToDescriptor} or
   *        {@link StatisticsType#nameToDescriptor}.
   * @return the value of the statistic
   * @throws IllegalArgumentException If no statistic exists with the specified
   *         <code>descriptor</code> or if the described statistic is not of type
   *         <code>double</code>.
   */
  double getDouble(StatisticDescriptor descriptor);

  /**
   * Returns the value of the statistic of type <code>double</code> at the given name.
   *
   * @param name the name of the statistic
   * @return the value of the statistic
   * @throws IllegalArgumentException If no statistic exists with name <code>name</code> or if the
   *         statistic named <code>name</code> is not of type <code>double</code>.
   */
  double getDouble(String name);

  /**
   * Returns the value of the identified statistic.
   *
   * @param descriptor a statistic descriptor obtained with {@link #nameToDescriptor} or
   *        {@link StatisticsType#nameToDescriptor}.
   * @return the value of the statistic
   * @throws IllegalArgumentException If the described statistic does not exist
   */
  Number get(StatisticDescriptor descriptor);

  /**
   * Returns the value of the named statistic.
   *
   * @param name the name of the statistic
   * @return the value of the statistic
   * @throws IllegalArgumentException If the named statistic does not exist
   */
  Number get(String name);

  /**
   * Returns the bits that represent the raw value of the described statistic.
   *
   * @param descriptor a statistic descriptor obtained with {@link #nameToDescriptor} or
   *        {@link StatisticsType#nameToDescriptor}.
   * @return the bits that represent the raw value of the named statistic
   * @throws IllegalArgumentException If the described statistic does not exist
   */
  long getRawBits(StatisticDescriptor descriptor);

  /**
   * Returns the bits that represent the raw value of the named statistic.
   *
   * @param name the name of the statistic
   * @return the bits that represent the raw value of the named statistic
   * @throws IllegalArgumentException If the named statistic does not exist
   */
  long getRawBits(String name);

  //////////////////////// inc() Methods ////////////////////////

  /**
   * Increments the value of the identified statistic of type <code>int</code> by the given amount.
   *
   * @param id a statistic id obtained with {@link #nameToId} or {@link StatisticsType#nameToId}.
   * @param delta the amount by which to increment the statistic value
   *
   * @throws ArrayIndexOutOfBoundsException If the id is invalid.
   * @deprecated as of Geode 1.10, use {@link #incLong(int, long)} instead
   */
  @Deprecated
  void incInt(int id, int delta);

  /**
   * Increments the value of the described statistic of type <code>int</code> by the given amount.
   *
   * @param descriptor the descriptor for the statistic to increment
   * @param delta the amount by which to increment the statistic value
   * @throws IllegalArgumentException If no statistic exists with the given <code>descriptor</code>
   *         or if the described statistic is not of type <code>int</code>.
   * @deprecated as of Geode 1.10, use {@link #incLong(StatisticDescriptor, long)} instead
   */
  @Deprecated
  void incInt(StatisticDescriptor descriptor, int delta);

  /**
   * Increments the value of the statistic of type <code>int</code> with the given name by a given
   * amount.
   *
   * @param name the name of the statistic to increment
   * @param delta the amount by which to increment the statistic value
   * @throws IllegalArgumentException If no statistic exists with name <code>name</code> or if the
   *         statistic named <code>name</code> is not of type <code>int</code>.
   * @deprecated as of Geode 1.10, use {@link #incLong(String, long)} instead
   */
  @Deprecated
  void incInt(String name, int delta);

  /**
   * Increments the value of the identified statistic of type <code>long</code> by the given amount.
   *
   * @param id a statistic id obtained with {@link #nameToId} or {@link StatisticsType#nameToId}.
   * @param delta the amount by which to increment the statistic value
   *
   * @throws ArrayIndexOutOfBoundsException If the id is invalid.
   */
  void incLong(int id, long delta);

  /**
   * Increments the value of the described statistic of type <code>long</code> by the given amount.
   *
   * @param descriptor the descriptor for the statistic to increment
   * @param delta the amount by which to increment the statistic value
   * @throws IllegalArgumentException If no statistic exists with the given <code>descriptor</code>
   *         or if the described statistic is not of type <code>long</code>.
   */
  void incLong(StatisticDescriptor descriptor, long delta);

  /**
   * Increments the value of the statistic of type <code>long</code> with the given name by a given
   * amount.
   *
   * @param name the name of the statistic to increment
   * @param delta the amount by which to increment the statistic value
   * @throws IllegalArgumentException If no statistic exists with name <code>name</code> or if the
   *         statistic named <code>name</code> is not of type <code>long</code>.
   */
  void incLong(String name, long delta);

  /**
   * Increments the value of the identified statistic of type <code>double</code> by the given
   * amount.
   *
   * @param id a statistic id obtained with {@link #nameToId} or {@link StatisticsType#nameToId}.
   * @param delta the amount by which to increment the statistic value
   *
   * @throws ArrayIndexOutOfBoundsException If the id is invalid.
   */
  void incDouble(int id, double delta);

  /**
   * Increments the value of the described statistic of type <code>double</code> by the given
   * amount.
   *
   * @param descriptor the descriptor for the statistic to increment
   * @param delta the amount by which to increment the statistic value
   *
   * @throws IllegalArgumentException If no statistic exists with the given <code>descriptor</code>
   *         or if the described statistic is not of type <code>double</code>.
   */
  void incDouble(StatisticDescriptor descriptor, double delta);

  /**
   * Increments the value of the statistic of type <code>double</code> with the given name by a
   * given amount.
   *
   * @param name the name of the statistic to increment
   * @param delta the amount by which to increment the statistic value
   *
   * @throws IllegalArgumentException If no statistic exists with name <code>name</code> or if the
   *         statistic named <code>name</code> is not of type <code>double</code>.
   */
  void incDouble(String name, double delta);

  /**
   * Provide a callback to compute the value of this statistic every sample interval and use that as
   * the value of the stat.
   * <p>
   * The callback should return quickly because it is invoked on a shared thread. It should not do
   * any expensive computations, network calls, or access any resources under locks that may be
   * locked by long running processes.
   * <p>
   * This callback will only be invoked if the distributed system property
   * statistic-sampling-enabled is set to true, and it will be invoked at intervals determined by
   * the statistic-sampling-rate.
   * <p>
   * Get methods are not guaranteed to recompute a new value, they may return the last sampled value
   *
   * @param id a statistic id obtained with {@link #nameToId} or {@link StatisticsType#nameToId}.
   * @param supplier a callback that will return the value of the stat. This replaces any previously
   *        registered supplier. If the passed in supplier is null, it will remove any existing
   *        supplier
   * @return the previously registered supplier, or null if there was no previously registered
   *         supplier
   * @throws IllegalArgumentException If the id is invalid.
   * @since Geode 1.0
   * @deprecated as of Geode 1.10, use {@link #setLongSupplier(int, LongSupplier)} instead
   */
  @Deprecated
  IntSupplier setIntSupplier(int id, IntSupplier supplier);

  /**
   * Provide a callback to compute the value of this statistic every sample interval and use that as
   * the value of the stat.
   * <p>
   * The callback should return quickly because it is invoked on a shared thread. It should not do
   * any expensive computations, network calls, or access any resources under locks that may be
   * locked by long running processes.
   * <p>
   * This callback will only be invoked if the distributed system property
   * statistic-sampling-enabled is set to true, and it will be invoked at intervals determined by
   * the statistic-sampling-rate.
   * <p>
   * Get methods are not guaranteed to recompute a new value, they may return the last sampled value
   *
   * @param name the name of the statistic to update
   * @param supplier a callback that will return the value of the stat. This replaces any previously
   *        registered supplier. If the passed in supplier is null, it will remove any existing
   *        supplier
   * @return the previously registered supplier, or null if there was no previously registered
   *         supplier
   * @throws IllegalArgumentException If no statistic exists with name <code>name</code> or if the
   *         statistic named <code>name</code> is not of type <code>int</code>.
   * @since Geode 1.0
   * @deprecated as of Geode 1.10, use {@link #setLongSupplier(String, LongSupplier)} instead
   */
  @Deprecated
  IntSupplier setIntSupplier(String name, IntSupplier supplier);


  /**
   * Provide a callback to compute the value of this statistic every sample interval and use that as
   * the value of the stat.
   * <p>
   * The callback should return quickly because it is invoked on a shared thread. It should not do
   * any expensive computations, network calls, or access any resources under locks that may be
   * locked by long running processes.
   * <p>
   * This callback will only be invoked if the distributed system property
   * statistic-sampling-enabled is set to true, and it will be invoked at intervals determined by
   * the statistic-sampling-rate.
   * <p>
   * Get methods are not guaranteed to recompute a new value, they may return the last sampled value
   *
   * @param descriptor the descriptor of the statistic to update
   * @param supplier a callback that will return the value of the stat. This replaces any previously
   *        registered supplier. If the passed in supplier is null, it will remove any existing
   *        supplier
   * @return the previously registered supplier, or null if there was no previously registered
   *         supplier
   * @throws IllegalArgumentException If no statistic exists with the given <code>descriptor</code>
   *         or if the described statistic is not of type <code>int</code>.
   * @since Geode 1.0
   * @deprecated as of Geode 1.10, use {@link #setLongSupplier(StatisticDescriptor, LongSupplier)}
   *             instead
   */
  @Deprecated
  IntSupplier setIntSupplier(StatisticDescriptor descriptor, IntSupplier supplier);

  /**
   * Provide a callback to compute the value of this statistic every sample interval and use that as
   * the value of the stat.
   * <p>
   * The callback should return quickly because it is invoked on a shared thread. It should not do
   * any expensive computations, network calls, or access any resources under locks that may be
   * locked by long running processes.
   * <p>
   * This callback will only be invoked if the distributed system property
   * statistic-sampling-enabled is set to true, and it will be invoked at intervals determined by
   * the statistic-sampling-rate.
   * <p>
   * Get methods are not guaranteed to recompute a new value, they may return the last sampled value
   *
   * @param id a statistic id obtained with {@link #nameToId} or {@link StatisticsType#nameToId}.
   * @param supplier a callback that will return the value of the stat. This replaces any previously
   *        registered supplier. If the passed in supplier is null, it will remove any existing
   *        supplier
   * @return the previously registered supplier, or null if there was no previously registered
   *         supplier
   * @throws IllegalArgumentException If the id is invalid.
   * @since Geode 1.0
   */
  LongSupplier setLongSupplier(int id, LongSupplier supplier);

  /**
   * Provide a callback to compute the value of this statistic every sample interval and use that as
   * the value of the stat.
   * <p>
   * The callback should return quickly because it is invoked on a shared thread. It should not do
   * any expensive computations, network calls, or access any resources under locks that may be
   * locked by long running processes.
   * <p>
   * This callback will only be invoked if the distributed system property
   * statistic-sampling-enabled is set to true, and it will be invoked at intervals determined by
   * the statistic-sampling-rate.
   * <p>
   * Get methods are not guaranteed to recompute a new value, they may return the last sampled value
   *
   * @param name the name of the statistic to update
   * @param supplier a callback that will return the value of the stat. This replaces any previously
   *        registered supplier. If the passed in supplier is null, it will remove any existing
   *        supplier
   * @return the previously registered supplier, or null if there was no previously registered
   *         supplier
   * @throws IllegalArgumentException If no statistic exists with name <code>name</code> or if the
   *         statistic named <code>name</code> is not of type <code>long</code>.
   */
  LongSupplier setLongSupplier(String name, LongSupplier supplier);


  /**
   * Provide a callback to compute the value of this statistic every sample interval and use that as
   * the value of the stat.
   * <p>
   * The callback should return quickly because it is invoked on a shared thread. It should not do
   * any expensive computations, network calls, or access any resources under locks that may be
   * locked by long running processes.
   * <p>
   * This callback will only be invoked if the distributed system property
   * statistic-sampling-enabled is set to true, and it will be invoked at intervals determined by
   * the statistic-sampling-rate.
   * <p>
   * Get methods are not guaranteed to recompute a new value, they may return the last sampled value
   *
   * @param descriptor the descriptor of the statistic to update
   * @param supplier a callback that will return the value of the stat. This replaces any previously
   *        registered supplier. If the passed in supplier is null, it will remove any existing
   *        supplier
   * @return the previously registered supplier, or null if there was no previously registered
   *         supplier
   * @throws IllegalArgumentException If no statistic exists with the given <code>descriptor</code>
   *         or if the described statistic is not of type <code>long</code>.
   * @since Geode 1.0
   */
  LongSupplier setLongSupplier(StatisticDescriptor descriptor, LongSupplier supplier);

  /**
   * Provide a callback to compute the value of this statistic every sample interval and use that as
   * the value of the stat.
   * <p>
   * The callback should return quickly because it is invoked on a shared thread. It should not do
   * any expensive computations, network calls, or access any resources under locks that may be
   * locked by double running processes.
   * <p>
   * This callback will only be invoked if the distributed system property
   * statistic-sampling-enabled is set to true, and it will be invoked at intervals determined by
   * the statistic-sampling-rate.
   * <p>
   * Get methods are not guaranteed to recompute a new value, they may return the last sampled value
   *
   * @param id a statistic id obtained with {@link #nameToId} or {@link StatisticsType#nameToId}.
   * @param supplier a callback that will return the value of the stat. This replaces any previously
   *        registered supplier. If the passed in supplier is null, it will remove any existing
   *        supplier
   * @return the previously registered supplier, or null if there was no previously registered
   *         supplier
   * @throws IllegalArgumentException If the id is invalid.
   * @since Geode 1.0
   */
  DoubleSupplier setDoubleSupplier(int id, DoubleSupplier supplier);

  /**
   * Provide a callback to compute the value of this statistic every sample interval and use that as
   * the value of the stat.
   * <p>
   * The callback should return quickly because it is invoked on a shared thread. It should not do
   * any expensive computations, network calls, or access any resources under locks that may be
   * locked by double running processes.
   * <p>
   * This callback will only be invoked if the distributed system property
   * statistic-sampling-enabled is set to true, and it will be invoked at intervals determined by
   * the statistic-sampling-rate.
   * <p>
   * Get methods are not guaranteed to recompute a new value, they may return the last sampled value
   *
   * @param name the name of the statistic to update
   * @param supplier a callback that will return the value of the stat. This replaces any previously
   *        registered supplier. If the passed in supplier is null, it will remove any existing
   *        supplier
   * @return the previously registered supplier, or null if there was no previously registered
   *         supplier
   * @throws IllegalArgumentException If no statistic exists with name <code>name</code> or if the
   *         statistic named <code>name</code> is not of type <code>double</code>.
   * @since Geode 1.0
   */
  DoubleSupplier setDoubleSupplier(String name, DoubleSupplier supplier);


  /**
   * Provide a callback to compute the value of this statistic every sample interval and use that as
   * the value of the stat.
   * <p>
   * The callback should return quickly because it is invoked on a shared thread. It should not do
   * any expensive computations, network calls, or access any resources under locks that may be
   * locked by double running processes.
   * <p>
   * This callback will only be invoked if the distributed system property
   * statistic-sampling-enabled is set to true, and it will be invoked at intervals determined by
   * the statistic-sampling-rate.
   * <p>
   * Get methods are not guaranteed to recompute a new value, they may return the last sampled value
   *
   * @param descriptor the descriptor of the statistic to update
   * @param supplier a callback that will return the value of the stat. This replaces any previously
   *        registered supplier. If the passed in supplier is null, it will remove any existing
   *        supplier
   * @return the previously registered supplier, or null if there was no previously registered
   *         supplier
   * @throws IllegalArgumentException If no statistic exists with the given <code>descriptor</code>
   *         or if the described statistic is not of type <code>double</code>.
   * @since Geode 1.0
   */
  DoubleSupplier setDoubleSupplier(StatisticDescriptor descriptor, DoubleSupplier supplier);
}
