org.jdiameter.client.impl.router.WeightedLeastConnectionsRouter Maven / Gradle / Ivy
/*
* TeleStax, Open Source Cloud Communications
* Copyright 2011-2016, Telestax Inc and individual contributors
* by the @authors tag.
*
* This program is free software: you can redistribute it and/or modify
* under the terms of the GNU Affero General Public License as
* published by the Free Software Foundation; either version 3 of
* the License, or (at your option) any later version.
*
* 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 Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see
*
*
* This requires that {@link IStatistic Statistics} for the following records are enabled:
* Peer,AppGenRequestPerSecond,NetGenRequestPerSecond In the client configuration, please use the following settings:
*
*
* ...
*
*
* ...
*
*
*
*
* @author Nils Sowen
* @see http://kb.linuxvirtualserver.org/wiki/Weighted_Least-Connection_Scheduling
*/
@SuppressWarnings("all") //3rd party lib
public class WeightedLeastConnectionsRouter extends RouterImpl implements IRouter {
private static final Logger logger = LoggerFactory.getLogger(WeightedLeastConnectionsRouter.class);
protected WeightedLeastConnectionsRouter(IRealmTable table, Configuration config) {
super(null, null, table, config, null);
}
public WeightedLeastConnectionsRouter(IContainer container, IConcurrentFactory concurrentFactory,
IRealmTable realmTable, Configuration config, MetaData aMetaData) {
super(container, concurrentFactory, realmTable, config, aMetaData);
}
/**
* Return peer with least connections
* {@url http://kb.linuxvirtualserver.org/wiki/Weighted_Least-Connection_Scheduling
* http://kb.linuxvirtualserver.org/wiki/Weighted_Least-Connection_Scheduling}
*
*
* The weighted least-connection scheduling is a superset of the least-connection scheduling, in which you can
* assign a performance weight to each real server. The servers with a higher weight value will receive a larger
* percentage of active connections at any one time. The default server weight is one, and the IPVS Administrator or
* monitoring program can assign any weight to real server. In the weighted least-connections scheduling, new
* network connection is assigned to a server which has the least ratio of the current active connection number to
* its weight.
*
* Supposing there is a server set S = {S0, S1, ..., Sn-1}, W(Si) is the weight of server Si; C(Si) is the current
* connection number of server Si; CSUM = ΣC(Si) (i=0, 1, .. , n-1) is the sum of current connection numbers;
*
* The new connection is assigned to the server j, in which (C(Sm) / CSUM)/ W(Sm) = min { (C(Si) / CSUM) / W(Si)}
* (i=0, 1, . , n-1), where W(Si) isn't zero Since the CSUM is a constant in this lookup, there is no need to divide
* by CSUM, the condition can be optimized as C(Sm) / W(Sm) = min { C(Si) / W(Si)} (i=0, 1, . , n-1), where W(Si)
* isn't zero
*
* Since division operation eats much more CPU cycles than multiply operation, and Linux does not allow float mode
* inside the kernel, the condition C(Sm)/W(Sm) > C(Si)/W(Si) can be optimized as C(Sm)*W(Si) > C(Si)*W(Sm). The
* scheduling should guarantee that a server will not be scheduled when its weight is zero. Therefore, the pseudo
* code of weighted least-connection scheduling algorithm is
*
*
*
* {@code
* for (m = 0; m < n; m++) {
* if (W(Sm) > 0) {
* for (i = m + 1; i < n; i++) {
* if (C(Sm) * W(Si) > C(Si) * W(Sm))
* m = i;
* }
* return Sm;
* }
* }
* return NULL;
* }
*
*
* The weighted least-connection scheduling algorithm requires additional division than the least-connection
* scheduling. In a hope to minimize the overhead of scheduling when servers have the same processing capacity, both
* the least-connection scheduling and the weighted least-connection scheduling algorithms are implemented.
*
* @param availablePeers list of peers that are in {@link PeerState#OKAY OKAY} state
*
* @return the selected peer according to algorithm
*
* @see http://kb.linuxvirtualserver.org/wiki/Weighted_Least-Connection_Scheduling
*/
@Override
public IPeer selectPeer(List availablePeers) {
int peerSize = availablePeers != null ? availablePeers.size() : 0;
// Return none if empty, or first if only one member found
if (peerSize <= 0) {
return null;
}
if (peerSize == 1) {
return availablePeers.iterator().next();
}
for (int m = 0; m < peerSize; peerSize++) {
IPeer peerM = availablePeers.get(m);
if (peerM.getRating() > 0) {
for (int i = m + 1; i < peerSize; i++) {
IPeer peerI = availablePeers.get(i);
if (getNumConnections(peerM) * peerI.getRating() > getNumConnections(peerI) * peerM.getRating()) {
m = i;
}
}
return availablePeers.get(m);
}
}
// Return first peer if anything did go wrong
return availablePeers.iterator().next();
}
/**
* Since num connections is not available, determine throughput by reading statistics and assume the load of the
* peer
*
* @param peer
*
* @return throughput indicator
*/
protected long getNumConnections(IPeer peer) {
if (peer == null) {
return 0;
}
IStatistic stats = peer.getStatistic();
// If no statistics are available, return zero
if (!stats.isEnabled()) {
if (logger.isDebugEnabled()) {
logger.debug("Statistics for peer are disabled. Please enable statistics in client config");
}
return 0;
}
// Requests per second initiated by Local Peer + Request initiated by Remote peer
String uri = peer.getUri() == null ? "local" : peer.getUri().toString();
long requests = getRecord(IStatisticRecord.Counters.AppGenRequestPerSecond.name() + '.' + uri, stats)
+ getRecord(IStatisticRecord.Counters.NetGenRequestPerSecond.name() + '.' + uri, stats);
// There are likely more requests than responses active
long connections = Math.max(0, requests);
if (logger.isTraceEnabled()) {
logger.trace("Active connections for {}: {}", peer, connections);
}
return connections;
}
/**
* Return statistics record value from given {@link IStatistic}
*
* @param record key to retrieve
* @param stats statistic object
*
* @return
*/
protected long getRecord(String record, IStatistic stats) {
if (record == null || stats == null) {
return 0;
}
IStatisticRecord statsRecord = stats.getRecordByName(record);
if (statsRecord == null) {
if (logger.isDebugEnabled()) {
logger.debug("Warning: no record for {}, available: {}", record, Arrays.toString(stats.getRecords()));
}
return 0;
}
return statsRecord.getValueAsLong();
}
}