net.java.truevfs.ext.insight.stats.IoStatistics.scala Maven / Gradle / Ivy

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Instruments the TrueVFS Kernel for statistics monitoring via JMX. Add the JAR artifact of this module to the run time class path to make its services available for service location in the client API modules.

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/*
 * Copyright (C) 2005-2013 Schlichtherle IT Services.
 * All rights reserved. Use is subject to license terms.
 */
package net.java.truevfs.ext.insight.stats

object IoStatistics {
  private val tenPowNine = BigInt(10) pow  9 // 1000000000
  private val twoPowTen  = BigInt( 2) pow 10 //       1024

  /** Returns I/O statistics with all properties set to zero. */
  def apply() = new IoStatistics(0, 0, 0, 0) // cannot cache because of timeMillis!
}

/**
  * An immutable record of statistics for I/O operations.
  *
  * @param  sequenceNumber the non-negative sequence number.
  * @throws IllegalArgumentException if any parameter value is negative.
  * @author Christian Schlichtherle
  */
final case class IoStatistics private (
  sequenceNumber: Long,
  nanosecondsTotal: Long,
  bytesTotal: Long,
  threadsTotal: Int,
  timeMillis: Long = System.currentTimeMillis
) extends Immutable {

  require(0 <= (sequenceNumber | nanosecondsTotal | bytesTotal | threadsTotal | timeMillis))

  def nanosecondsPerOperation =
    if (0 == sequenceNumber) 0L else nanosecondsTotal / sequenceNumber

  def bytesPerOperation =
    if (0 == sequenceNumber) 0 else (bytesTotal / sequenceNumber).toInt

  def kilobytesPerSecond = {
    import IoStatistics._
    if (0 == nanosecondsTotal) 0L
    else (BigInt(bytesTotal) * tenPowNine /
          (BigInt(nanosecondsTotal) * twoPowTen)).toLong
  }

  /**
    * Logs an I/O operation with the given sample data and returns a new
    * object to reflect the updated statistics at the current system time.
    * If any property would overflow to a negative value as a result of the
    * update, then the returned object will simply have its sequence number
    * set to one (!) and its other properties will be reset to reflect only
    * the given parameter values at the current system time.
    * In other words, the statistics would restart from fresh.
    *
    * @param  nanosDelta the execution time.
    * @param  bytesDelta the number of bytes read or written.
    * @return A new object which reflects the updated statistics at the
    *         current system time.
    * @throws IllegalArgumentException if any parameter value is negative.
    */
  @throws(classOf[IllegalArgumentException])
  def log(nanosDelta: Long, bytesDelta: Long, threadsTotal: Int) = {
    require(0 <= (nanosDelta | bytesDelta | threadsTotal))
    try {
      new IoStatistics(sequenceNumber + 1,
                       nanosecondsTotal + nanosDelta,
                       bytesTotal + bytesDelta,
                       threadsTotal)
    } catch {
      case _: IllegalArgumentException =>
        new IoStatistics(1, nanosDelta, bytesDelta, 1)
    }
  }

  def equalsIgnoreTime(that: IoStatistics) =
    this.sequenceNumber == that.sequenceNumber &&
    this.nanosecondsTotal == that.nanosecondsTotal &&
    this.bytesTotal == that.bytesTotal &&
    this.threadsTotal == that.threadsTotal
}