/*
* Copyright (c) 2014 Spotify AB.
*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
package com.spotify.helios.common;
import com.google.common.base.Optional;
import com.google.common.base.Supplier;
import com.google.common.base.Throwables;
import com.google.common.collect.ImmutableList;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.xbill.DNS.DClass;
import org.xbill.DNS.Lookup;
import org.xbill.DNS.Record;
import org.xbill.DNS.SRVRecord;
import org.xbill.DNS.TextParseException;
import org.xbill.DNS.Type;
import java.net.URI;
import java.net.URISyntaxException;
import java.util.List;
import static java.lang.String.format;
import static java.lang.System.getenv;
public abstract class Resolver {
private static final String SRV_FORMAT = env("HELIOS_SRV_FORMAT", "_%s._http.%s");
private static String env(final String name, final String defaultValue) {
return Optional.fromNullable(getenv(name)).or(defaultValue);
}
private static final Logger log = LoggerFactory.getLogger(Resolver.class);
public static Supplier<List<URI>> supplier(final String srvName, final String domain) {
return new Supplier<List<URI>>() {
@Override
public List<URI> get() {
return resolve(srvName, domain);
}
};
}
public static List<URI> resolve(final String srvName, final String domain) {
final String name = srv(srvName, domain);
final Lookup lookup;
try {
lookup = new Lookup(name, Type.SRV, DClass.IN);
} catch (TextParseException e) {
throw new IllegalArgumentException("unable to create lookup for name: " + name, e);
}
Record[] queryResult = lookup.run();
switch (lookup.getResult()) {
case Lookup.SUCCESSFUL:
final ImmutableList.Builder<URI> endpoints = ImmutableList.builder();
for (Record record : queryResult) {
if (record instanceof SRVRecord) {
SRVRecord srv = (SRVRecord) record;
endpoints.add(http(srv.getTarget().toString(), srv.getPort()));
}
}
return endpoints.build();
case Lookup.HOST_NOT_FOUND:
// fallthrough
case Lookup.TYPE_NOT_FOUND:
log.warn("No results returned for query '{}'", name);
return ImmutableList.of();
default:
throw new HeliosRuntimeException(String.format("Lookup of '%s' failed with code: %d - %s ",
name, lookup.getResult(),
lookup.getErrorString()));
}
}
private static URI http(final String host, final int port) {
final URI endpoint;
try {
endpoint = new URI("http", null, host, port, null, null, null);
} catch (URISyntaxException e) {
throw Throwables.propagate(e);
}
return endpoint;
}
private static String srv(final String name, final String domain) {
return format(SRV_FORMAT, name, domain);
}
}