2014-09-19 15:36:32 +02:00
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/*
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* Copyright 2014 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.buffer.Unpooled;
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import io.netty.channel.ChannelFuture;
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import io.netty.channel.ChannelFutureListener;
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import io.netty.handler.codec.dns.DnsQuery;
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import io.netty.handler.codec.dns.DnsQuestion;
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import io.netty.handler.codec.dns.DnsResource;
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import io.netty.handler.codec.dns.DnsResponse;
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import io.netty.handler.codec.dns.DnsType;
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import io.netty.resolver.dns.DnsNameResolver.DnsCacheEntry;
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import io.netty.util.concurrent.Promise;
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import io.netty.util.concurrent.ScheduledFuture;
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import io.netty.util.internal.OneTimeTask;
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import io.netty.util.internal.StringUtil;
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import io.netty.util.internal.ThreadLocalRandom;
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import io.netty.util.internal.logging.InternalLogger;
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import io.netty.util.internal.logging.InternalLoggerFactory;
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import java.net.InetSocketAddress;
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import java.net.UnknownHostException;
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import java.util.Iterator;
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import java.util.concurrent.TimeUnit;
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final class DnsQueryContext {
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private static final InternalLogger logger = InternalLoggerFactory.getInstance(DnsQueryContext.class);
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private final DnsNameResolver parent;
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private final Promise<DnsResponse> promise;
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private final int id;
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private final DnsQuestion question;
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private final DnsResource optResource;
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private final Iterator<InetSocketAddress> nameServerAddresses;
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private final boolean recursionDesired;
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private final int maxTries;
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private int remainingTries;
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private volatile ScheduledFuture<?> timeoutFuture;
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private StringBuilder trace;
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DnsQueryContext(DnsNameResolver parent,
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Iterable<InetSocketAddress> nameServerAddresses,
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DnsQuestion question, Promise<DnsResponse> promise) {
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this.parent = parent;
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this.promise = promise;
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this.question = question;
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id = allocateId();
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recursionDesired = parent.isRecursionDesired();
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maxTries = parent.maxTriesPerQuery();
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remainingTries = maxTries;
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optResource = new DnsResource("", DnsType.OPT, parent.maxPayloadSizeClass(), 0, Unpooled.EMPTY_BUFFER);
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this.nameServerAddresses = nameServerAddresses.iterator();
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}
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private int allocateId() {
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int id = ThreadLocalRandom.current().nextInt(parent.promises.length());
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final int maxTries = parent.promises.length() << 1;
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int tries = 0;
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for (;;) {
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if (parent.promises.compareAndSet(id, null, this)) {
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return id;
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}
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id = id + 1 & 0xFFFF;
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if (++ tries >= maxTries) {
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throw new IllegalStateException("query ID space exhausted: " + question);
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}
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}
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}
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Promise<DnsResponse> promise() {
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return promise;
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}
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DnsQuestion question() {
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return question;
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}
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ScheduledFuture<?> timeoutFuture() {
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return timeoutFuture;
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}
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void query() {
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final DnsQuestion question = this.question;
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if (remainingTries <= 0 || !nameServerAddresses.hasNext()) {
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parent.promises.set(id, null);
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int tries = maxTries - remainingTries;
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UnknownHostException cause;
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if (tries > 1) {
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cause = new UnknownHostException(
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"failed to resolve " + question + " after " + tries + " attempts:" +
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trace);
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} else {
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cause = new UnknownHostException("failed to resolve " + question + ':' + trace);
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}
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cache(question, cause);
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promise.tryFailure(cause);
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return;
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}
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remainingTries --;
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final InetSocketAddress nameServerAddr = nameServerAddresses.next();
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final DnsQuery query = new DnsQuery(id, nameServerAddr);
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query.addQuestion(question);
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query.header().setRecursionDesired(recursionDesired);
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query.addAdditionalResource(optResource);
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if (logger.isDebugEnabled()) {
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2014-11-18 21:28:45 +01:00
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logger.debug("{} WRITE: [{}: {}], {}", parent.ch, id, nameServerAddr, question);
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}
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sendQuery(query, nameServerAddr);
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}
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private void sendQuery(final DnsQuery query, final InetSocketAddress nameServerAddr) {
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if (parent.bindFuture.isDone()) {
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writeQuery(query, nameServerAddr);
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} else {
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parent.bindFuture.addListener(new ChannelFutureListener() {
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@Override
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public void operationComplete(ChannelFuture future) throws Exception {
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if (future.isSuccess()) {
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writeQuery(query, nameServerAddr);
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} else {
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promise.tryFailure(future.cause());
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}
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}
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});
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2014-09-19 15:36:32 +02:00
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}
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2014-11-18 21:28:45 +01:00
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}
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2014-09-19 15:36:32 +02:00
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2014-11-18 21:28:45 +01:00
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private void writeQuery(final DnsQuery query, final InetSocketAddress nameServerAddr) {
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final ChannelFuture writeFuture = parent.ch.writeAndFlush(query);
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2014-09-19 15:36:32 +02:00
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if (writeFuture.isDone()) {
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onQueryWriteCompletion(writeFuture, nameServerAddr);
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} else {
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writeFuture.addListener(new ChannelFutureListener() {
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@Override
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public void operationComplete(ChannelFuture future) throws Exception {
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onQueryWriteCompletion(writeFuture, nameServerAddr);
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}
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});
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}
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}
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private void onQueryWriteCompletion(ChannelFuture writeFuture, final InetSocketAddress nameServerAddr) {
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if (!writeFuture.isSuccess()) {
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retry(nameServerAddr, "failed to send a query: " + writeFuture.cause());
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return;
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}
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// Schedule a query timeout task if necessary.
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final long queryTimeoutMillis = parent.queryTimeoutMillis();
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if (queryTimeoutMillis > 0) {
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timeoutFuture = parent.ch.eventLoop().schedule(new OneTimeTask() {
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@Override
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public void run() {
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if (promise.isDone()) {
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// Received a response before the query times out.
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return;
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}
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retry(nameServerAddr, "query timed out after " + queryTimeoutMillis + " milliseconds");
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}
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}, queryTimeoutMillis, TimeUnit.MILLISECONDS);
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}
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}
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void retry(InetSocketAddress nameServerAddr, String message) {
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if (promise.isCancelled()) {
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return;
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}
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if (trace == null) {
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trace = new StringBuilder(128);
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}
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trace.append(StringUtil.NEWLINE);
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trace.append("\tfrom ");
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trace.append(nameServerAddr);
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trace.append(": ");
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trace.append(message);
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query();
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}
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private void cache(final DnsQuestion question, Throwable cause) {
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final int negativeTtl = parent.negativeTtl();
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if (negativeTtl == 0) {
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return;
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}
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parent.cache(question, new DnsCacheEntry(cause), negativeTtl);
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}
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}
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