5a2d04684e
Motivation: A single DNS query may follow many different paths through resolver-dns. The query may fail for various reasons related to the DNS protocol, general IO errors, it may be cancelled due to the query count being exceeded, or other reasons. A query may also result in other queries as we follow the DNS protocol (e.g. redirects, CNAME, etc...). It is currently impossible to collect information about the life cycle of an individual query though resolver-dns. This information may be valuable when considering which DNS servers are preferred over others. Modifications: - Introduce an interface which can provide visibility into all the potential outcomes of an individual DNS query Result: resolver-dns provides visibility into individual DNS queries which can be used to avoid poorly performing DNS servers.
62 lines
1.7 KiB
Java
62 lines
1.7 KiB
Java
/*
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* Copyright 2017 The Netty Project
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*
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* The Netty Project licenses this file to you under the Apache License,
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* version 2.0 (the "License"); you may not use this file except in compliance
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* with the License. You may obtain a copy of the License at:
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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*/
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package io.netty.resolver.dns;
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import io.netty.channel.ChannelFuture;
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import io.netty.handler.codec.dns.DnsQuestion;
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import io.netty.handler.codec.dns.DnsResponseCode;
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import java.net.InetSocketAddress;
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import java.util.List;
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final class NoopDnsQueryLifecycleObserver implements DnsQueryLifecycleObserver {
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static final NoopDnsQueryLifecycleObserver INSTANCE = new NoopDnsQueryLifecycleObserver();
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private NoopDnsQueryLifecycleObserver() {
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}
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@Override
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public void queryWritten(InetSocketAddress dnsServerAddress, ChannelFuture future) {
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}
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@Override
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public void queryCancelled(int queriesRemaining) {
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}
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@Override
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public DnsQueryLifecycleObserver queryRedirected(List<InetSocketAddress> nameServers) {
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return this;
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}
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@Override
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public DnsQueryLifecycleObserver queryCNAMEd(DnsQuestion cnameQuestion) {
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return this;
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}
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@Override
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public DnsQueryLifecycleObserver queryNoAnswer(DnsResponseCode code) {
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return this;
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}
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@Override
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public void queryFailed(Throwable cause) {
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}
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@Override
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public void querySucceed() {
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}
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}
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