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// Copyright 2017 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.messagebus.network.rpc;
import com.yahoo.jrt.slobrok.api.IMirror;
import com.yahoo.jrt.slobrok.api.Mirror;
import java.util.List;
import java.util.concurrent.ThreadLocalRandom;
/**
* An RPCService represents a set of remote sessions matching a service pattern. The sessions are monitored using the
* slobrok. If multiple sessions are available, round robin is used to balance load between them.
*
* @author havardpe
*/
public class RPCService {
private final IMirror mirror;
private final String pattern;
private int addressIdx = ThreadLocalRandom.current().nextInt(Integer.MAX_VALUE);
private int addressGen = 0;
private List<Mirror.Entry> addressList = null;
/**
* Create a new RPCService backed by the given network and using the given service pattern.
*
* @param mirror The naming server to send queries to.
* @param pattern The pattern to use when querying.
*/
public RPCService(IMirror mirror, String pattern) {
this.mirror = mirror;
this.pattern = pattern;
}
/**
* Resolve a concrete address from this service. This service may represent multiple remote sessions, so this will
* select one that is online.
*
* @return A concrete service address.
*/
public RPCServiceAddress resolve() {
if (pattern.startsWith("tcp/")) {
int pos = pattern.lastIndexOf('/');
if (pos > 0 && pos < pattern.length() - 1) {
RPCServiceAddress ret = new RPCServiceAddress(pattern, pattern.substring(0, pos));
if (!ret.isMalformed()) {
return ret;
}
}
} else {
if (addressGen != mirror.updates()) {
addressGen = mirror.updates();
addressList = mirror.lookup(pattern);
}
if (addressList != null && !addressList.isEmpty()) {
addressIdx = ++addressIdx % addressList.size();
Mirror.Entry entry = addressList.get(addressIdx);
return new RPCServiceAddress(entry.getName(), entry.getSpec());
}
}
return null;
}
/**
* Returns the pattern used when querying for the naming server for addresses. This is given at construtor time.
*
* @return The service pattern.
*/
String getPattern() {
return pattern;
}
}
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