package com.bigdata.service;
import com.bigdata.service.LoadBalancerService.UpdateTask;
/**
* Per-host metadata and a score for that host which gets updated
* periodically by {@link UpdateTask}. {@link HostScore}s are a
* <em>resource utilization</em> measure. They are higher for a host which
* is more highly utilized. There are several ways to look at the score,
* including the {@link #rawScore}, the {@link #rank}, and the
* {@link #drank normalized double-precision rank}. The ranks move in the
* same direction as the {@link #rawScore}s - a higher rank indicates
* higher utilization. The least utilized host is always rank zero (0). The
* most utilized host is always in the last rank.
*
* @author <a href="mailto:thompsonbry@users.sourceforge.net">Bryan Thompson</a>
* @version $Id$
*/
public class HostScore implements Comparable<HostScore> {
public final String hostname;
/** The raw score computed for that service. */
public final double rawScore;
/** The normalized score computed for that service. */
public double score;
/** The rank in [0:#scored]. This is an index into the Scores[]. */
public int rank = -1;
/** The normalized double precision rank in [0.0:1.0]. */
public double drank = -1d;
/**
* Constructor variant used when you do not have performance counters
* for the host and could not compute its rawScore.
*
* @param hostname
*/
public HostScore(String hostname) {
this(hostname, 0d);
}
/**
* Constructor variant used when you have computed the rawStore.
*
* @param hostname
* @param rawScore
*/
public HostScore(String hostname, double rawScore) {
assert hostname != null;
assert hostname.length() > 0;
this.hostname = hostname;
this.rawScore = rawScore;
}
public String toString() {
return "HostScore{hostname=" + hostname + ", rawScore=" + rawScore
+ ", score=" + score + ", rank=" + rank + ", drank=" + drank
+ "}";
}
/**
* Places elements into order by ascending {@link #rawScore} (aka
* increasing utilization). The {@link #hostname} is used to break any
* ties.
*/
public int compareTo(HostScore arg0) {
if (rawScore < arg0.rawScore) {
return -1;
} else if (rawScore > arg0.rawScore) {
return 1;
}
return hostname.compareTo(arg0.hostname);
}
/**
* Normalizes a raw score in the context of totals for some host.
*
* @param rawScore
* The raw score.
* @param totalRawScore
* The raw score computed from the totals.
*
* @return The normalized score.
*/
static public double normalize(double rawScore, double totalRawScore) {
if (totalRawScore == 0d) {
return 0d;
}
return rawScore / totalRawScore;
}
}