/*
* Druid - a distributed column store.
* Copyright (C) 2012, 2013 Metamarkets Group Inc.
*
* 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; either version 2
* 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 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*/
package io.druid.server.router;
import com.google.inject.Inject;
import com.metamx.common.ISE;
import com.metamx.common.Pair;
import com.metamx.emitter.EmittingLogger;
import io.druid.client.selector.Server;
import io.druid.curator.discovery.ServerDiscoverySelector;
import io.druid.query.Query;
import java.util.concurrent.ConcurrentHashMap;
/**
*/
public class QueryHostFinder<T>
{
private static EmittingLogger log = new EmittingLogger(QueryHostFinder.class);
private final TieredBrokerHostSelector hostSelector;
private final ConcurrentHashMap<String, Server> serverBackup = new ConcurrentHashMap<String, Server>();
@Inject
public QueryHostFinder(
TieredBrokerHostSelector hostSelector
)
{
this.hostSelector = hostSelector;
}
public Server findServer(Query<T> query)
{
final Pair<String, ServerDiscoverySelector> selected = hostSelector.select(query);
return findServerInner(selected);
}
public Server findDefaultServer()
{
final Pair<String, ServerDiscoverySelector> selected = hostSelector.getDefaultLookup();
return findServerInner(selected);
}
public String getHost(Query<T> query)
{
Server server = findServer(query);
if (server == null) {
log.makeAlert(
"Catastrophic failure! No servers found at all! Failing request!"
).emit();
throw new ISE("No server found for query[%s]", query);
}
log.debug("Selected [%s]", server.getHost());
return server.getHost();
}
public String getDefaultHost()
{
Server server = findDefaultServer();
if (server == null) {
log.makeAlert(
"Catastrophic failure! No servers found at all! Failing request!"
).emit();
throw new ISE("No default server found!");
}
return server.getHost();
}
private Server findServerInner(final Pair<String, ServerDiscoverySelector> selected)
{
if (selected == null) {
log.error("Danger, Will Robinson! Unable to find any brokers!");
}
final String serviceName = selected == null ? hostSelector.getDefaultServiceName() : selected.lhs;
final ServerDiscoverySelector selector = selected == null ? null : selected.rhs;
Server server = selector == null ? null : selector.pick();
if (server == null) {
log.error(
"WTF?! No server found for serviceName[%s]. Using backup",
serviceName
);
server = serverBackup.get(serviceName);
if (server == null) {
log.error(
"WTF?! No backup found for serviceName[%s]. Using default[%s]",
serviceName,
hostSelector.getDefaultServiceName()
);
server = serverBackup.get(hostSelector.getDefaultServiceName());
}
}
if (server != null) {
serverBackup.put(serviceName, server);
}
return server;
}
}