/*
* The MIT License
*
* Copyright (c) 2004-2010, Sun Microsystems, Inc., Kohsuke Kawaguchi
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package hudson.model;
import hudson.model.Queue.Task;
import hudson.model.queue.MappingWorksheet;
import hudson.model.queue.MappingWorksheet.ExecutorChunk;
import hudson.model.queue.MappingWorksheet.Mapping;
import hudson.util.ConsistentHash;
import hudson.util.ConsistentHash.Hash;
import java.util.ArrayList;
import java.util.List;
import java.util.logging.Logger;
/**
* Strategy that decides which {@link Task} gets run on which {@link Executor}.
*
* @author Kohsuke Kawaguchi
* @since 1.301
*/
public abstract class LoadBalancer /*implements ExtensionPoint*/ {
/**
* Chooses the executor(s) to carry out the build for the given task.
*
* <p>
* This method is invoked from different threads, but the execution is serialized by the caller.
* The thread that invokes this method always holds a lock to {@link Queue}, so queue contents
* can be safely introspected from this method, if that information is necessary to make
* decisions.
*
* @param task
* The task whose execution is being considered. Never null.
* @param worksheet
* The work sheet that represents the matching that needs to be made.
* The job of this method is to determine which work units on this worksheet
* are executed on which executors (also on this worksheet.)
*
* @return
* Build up the mapping by using the given worksheet and return it.
* Return null if you don't want the task to be executed right now,
* in which case this method will be called some time later with the same task.
*/
public abstract Mapping map(Task task, MappingWorksheet worksheet);
/**
* Uses a consistent hash for scheduling.
*/
public static final LoadBalancer CONSISTENT_HASH = new LoadBalancer() {
@Override
public Mapping map(Task task, MappingWorksheet ws) {
// build consistent hash for each work chunk
List<ConsistentHash<ExecutorChunk>> hashes = new ArrayList<ConsistentHash<ExecutorChunk>>(ws.works.size());
for (int i=0; i<ws.works.size(); i++) {
ConsistentHash<ExecutorChunk> hash = new ConsistentHash<ExecutorChunk>(new Hash<ExecutorChunk>() {
public String hash(ExecutorChunk node) {
return node.getName();
}
});
for (ExecutorChunk ec : ws.works(i).applicableExecutorChunks())
hash.add(ec,ec.size()*100);
hashes.add(hash);
}
// do a greedy assignment
Mapping m = ws.new Mapping();
assert m.size()==ws.works.size(); // just so that you the reader of the source code don't get confused with the for loop index
if (assignGreedily(m,task,hashes,0)) {
assert m.isCompletelyValid();
return m;
} else
return null;
}
private boolean assignGreedily(Mapping m, Task task, List<ConsistentHash<ExecutorChunk>> hashes, int i) {
if (i==hashes.size()) return true; // fully assigned
String key = task.getFullDisplayName() + (i>0 ? String.valueOf(i) : "");
for (ExecutorChunk ec : hashes.get(i).list(key)) {
// let's attempt this assignment
m.assign(i,ec);
if (m.isPartiallyValid() && assignGreedily(m,task,hashes,i+1))
return true; // successful greedily allocation
// otherwise 'ec' wasn't a good fit for us. try next.
}
// every attempt failed
m.assign(i,null);
return false;
}
};
/**
* Traditional implementation of this.
*
* @deprecated as of 1.377
* The only implementation in the core now is the one based on consistent hash.
*/
public static final LoadBalancer DEFAULT = CONSISTENT_HASH;
/**
* Wraps this {@link LoadBalancer} into a decorator that tests the basic sanity of the implementation.
* Only override this if you find some of the checks excessive, but beware that it's like driving without a seat belt.
*/
protected LoadBalancer sanitize() {
final LoadBalancer base = this;
return new LoadBalancer() {
@Override
public Mapping map(Task task, MappingWorksheet worksheet) {
if (Queue.ifBlockedByHudsonShutdown(task)) {
// if we are quieting down, don't start anything new so that
// all executors will be eventually free.
return null;
}
return base.map(task, worksheet);
}
/**
* Double-sanitization is pointless.
*/
@Override
protected LoadBalancer sanitize() {
return this;
}
private final Logger LOGGER = Logger.getLogger(LoadBalancer.class.getName());
};
}
}