/**
Copyright (C) SYSTAP, LLC DBA Blazegraph 2006-2016. All rights reserved.
Contact:
SYSTAP, LLC DBA Blazegraph
2501 Calvert ST NW #106
Washington, DC 20008
licenses@blazegraph.com
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
package com.bigdata.rdf.sail.webapp.lbs;
import java.util.Comparator;
import com.bigdata.counters.AbstractStatisticsCollector;
/**
* Helper class pairs a hostname and the normalized availabilty for that host.
* The availability is based on (normalized) <code>1 - LOAD</code> for the host.
* The <code>LOAD</code> is computed using the {@link IHostMetrics} and an
* {@link IHostScoringRule} for computing the workload of a host from those
* metrics. The availability is then computed from the LOAD and normalized.
*
* @author <a href="mailto:thompsonbry@users.sourceforge.net">Bryan Thompson</a>
*/
public class HostScore {
/** The hostname. */
private final String hostname;
/**
* <code>true</code> iff the host is this host.
*/
private final boolean thisHost;
/**
* The normalized availability for the host.
*/
private final double availability;
/**
* Return the normalized availability for the host. Load balancing decision
* are based on this normalized {@link #getAvailability() score} (work is
* assigned to hosts in inverse proportion to the normalized load of the
* host).
*/
public double getAvailability() {
return availability;
}
/** Return the hostname. */
public String getHostname() {
return hostname;
}
/**
* Return <code>true</code> iff the host is this host.
*/
public boolean isThisHost() {
return thisHost;
}
@Override
public String toString() {
return "HostScore"//
+ "{hostname=" + hostname //
+ ", thisHost=" + thisHost//
+ ", availabilty=" + availability //
+ "}";
}
/**
*
* @param hostname
* The hostname (required, must be non-empty).
* @param availability
* The normalized availability score for this host.
*/
public HostScore(//
final String hostname,//
final double availability
) {
if (hostname == null)
throw new IllegalArgumentException();
if (hostname.trim().length() == 0)
throw new IllegalArgumentException();
if (availability < 0d || availability > 1d)
throw new IllegalArgumentException();
this.hostname = hostname;
this.availability = availability;
this.thisHost = AbstractStatisticsCollector.fullyQualifiedHostName
.equals(hostname);
}
/**
* Places elements into order by decreasing {@link #getAvailability() normalized
* load}. The {@link #getHostname()} is used to break any ties.
*/
public final static Comparator<HostScore> COMPARE_BY_SCORE = new Comparator<HostScore>() {
@Override
public int compare(final HostScore t1, final HostScore t2) {
if (t1.availability < t2.availability) {
return 1;
} else if (t1.availability > t2.availability) {
return -1;
}
return t1.hostname.compareTo(t2.hostname);
}
};
/**
* Orders by hostname. This provides a stable way of viewing the data in
* <code>/bigdata/status</code>.
*/
public final static Comparator<HostScore> COMPARE_BY_HOSTNAME = new Comparator<HostScore>() {
@Override
public int compare(final HostScore t1, final HostScore t2) {
return t1.hostname.compareTo(t2.hostname);
}
};
}