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Randomly choose a server when multiple best servers are available (#3822) 

* Randomly choose a server when multiple best servers are available

* Use one pass instead of two

* Fix code style issues
This commit is contained in:
Niketh Sabbineni 2017-01-05 21:34:05 -08:00 committed by Parag Jain
parent 3c63cff57a
commit a5f82e8acf
1 changed files with 11 additions and 3 deletions
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14
server/src/main/java/io/druid/server/coordinator/CostBalancerStrategy.java
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@ -32,6 +32,7 @@ import io.druid.timeline.DataSegment;
import org.apache.commons.math3.util.FastMath; import org.apache.commons.math3.util.FastMath;
import org.joda.time.Interval; import org.joda.time.Interval;
import java.util.ArrayList;
import java.util.List; import java.util.List;
import java.util.concurrent.Callable; import java.util.concurrent.Callable;
@ -348,13 +349,20 @@ public class CostBalancerStrategy implements BalancerStrategy
} }
final ListenableFuture<List<Pair<Double, ServerHolder>>> resultsFuture = Futures.allAsList(futures); final ListenableFuture<List<Pair<Double, ServerHolder>>> resultsFuture = Futures.allAsList(futures);
final List<Pair<Double, ServerHolder>> bestServers = new ArrayList<>();
bestServers.add(bestServer);
try { try {
for (Pair<Double, ServerHolder> server : resultsFuture.get()) { for (Pair<Double, ServerHolder> server : resultsFuture.get()) {
if (server.lhs < bestServer.lhs) { if (server.lhs <= bestServers.get(0).lhs) {
bestServer = server; if (server.lhs < bestServers.get(0).lhs) {
bestServers.clear();
}
bestServers.add(server);
} }
} }
// Randomly choose a server from the best servers
bestServer = bestServers.get((int) Math.random() * bestServers.size());
} }
catch (Exception e) { catch (Exception e) {
log.makeAlert(e, "Cost Balancer Multithread strategy wasn't able to complete cost computation.").emit(); log.makeAlert(e, "Cost Balancer Multithread strategy wasn't able to complete cost computation.").emit();