/* * Copyright (c) 2015 Spotify AB * * Licensed 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.dns; import static java.util.concurrent.TimeUnit.HOURS; import static java.util.concurrent.TimeUnit.SECONDS; import com.spotify.dns.statistics.DnsReporter; import java.net.UnknownHostException; import java.time.Duration; import java.util.List; import org.xbill.DNS.ExtendedResolver; import org.xbill.DNS.Resolver; /** * Provides builders for configuring and instantiating {@link DnsSrvResolver}s. */ public final class DnsSrvResolvers { private static final int DEFAULT_DNS_TIMEOUT_SECONDS = 5; private static final int DEFAULT_RETENTION_DURATION_HOURS = 2; public static DnsSrvResolverBuilder newBuilder() { return new DnsSrvResolverBuilder(); } public static final class DnsSrvResolverBuilder { private final DnsReporter reporter; private final boolean retainData; private final boolean cacheLookups; private final long dnsLookupTimeoutMillis; private final long retentionDurationMillis; private final List<String> servers; private DnsSrvResolverBuilder() { this(null, false, false, SECONDS.toMillis(DEFAULT_DNS_TIMEOUT_SECONDS), HOURS.toMillis(DEFAULT_RETENTION_DURATION_HOURS), null); } private DnsSrvResolverBuilder( DnsReporter reporter, boolean retainData, boolean cacheLookups, long dnsLookupTimeoutMillis, long retentionDurationMillis, List<String> servers) { this.reporter = reporter; this.retainData = retainData; this.cacheLookups = cacheLookups; this.dnsLookupTimeoutMillis = dnsLookupTimeoutMillis; this.retentionDurationMillis = retentionDurationMillis; this.servers = servers; } public DnsSrvResolver build() { Resolver resolver; try { // If the user specified DNS servers, create a new ExtendedResolver which uses them. // Otherwise, use the default constructor. That will use the servers in ResolverConfig, // or if that's empty, localhost. resolver = servers == null ? new ExtendedResolver() : new ExtendedResolver(servers.toArray(new String[servers.size()])); } catch (UnknownHostException e) { throw new RuntimeException(e); } // Configure the Resolver to use our timeouts. final Duration timeoutDuration = Duration.ofMillis(dnsLookupTimeoutMillis); resolver.setTimeout(timeoutDuration); LookupFactory lookupFactory = new SimpleLookupFactory(resolver); if (cacheLookups) { lookupFactory = new CachingLookupFactory(lookupFactory); } DnsSrvResolver result = new XBillDnsSrvResolver(lookupFactory); if (reporter != null) { result = new MeteredDnsSrvResolver(result, reporter); } if (retainData) { result = new RetainingDnsSrvResolver(result, retentionDurationMillis); } return result; } public DnsSrvResolverBuilder metered(DnsReporter reporter) { return new DnsSrvResolverBuilder(reporter, retainData, cacheLookups, dnsLookupTimeoutMillis, retentionDurationMillis, servers); } public DnsSrvResolverBuilder retainingDataOnFailures(boolean retainData) { return new DnsSrvResolverBuilder(reporter, retainData, cacheLookups, dnsLookupTimeoutMillis, retentionDurationMillis, servers); } public DnsSrvResolverBuilder cachingLookups(boolean cacheLookups) { return new DnsSrvResolverBuilder(reporter, retainData, cacheLookups, dnsLookupTimeoutMillis, retentionDurationMillis, servers); } public DnsSrvResolverBuilder dnsLookupTimeoutMillis(long dnsLookupTimeoutMillis) { return new DnsSrvResolverBuilder(reporter, retainData, cacheLookups, dnsLookupTimeoutMillis, retentionDurationMillis, servers); } public DnsSrvResolverBuilder retentionDurationMillis(long retentionDurationMillis) { return new DnsSrvResolverBuilder(reporter, retainData, cacheLookups, dnsLookupTimeoutMillis, retentionDurationMillis, servers); } /** * Allows the user to specify which DNS servers should be used to perform DNS lookups. Servers * can be specified using either hostname or IP address. If not specified, the underlying DNS * library will determine which servers to use according to the steps documented in * <a href="https://github.com/dnsjava/dnsjava/blob/master/org/xbill/DNS/ResolverConfig.java"> * ResolverConfig.java</a> * @param servers the DNS servers to use * @return this builder */ public DnsSrvResolverBuilder servers(List<String> servers) { return new DnsSrvResolverBuilder(reporter, retainData, cacheLookups, dnsLookupTimeoutMillis, retentionDurationMillis, servers); } } private DnsSrvResolvers() { // prevent instantiation } }