Motivation: JCTools supports both non-unsafe, unsafe versions of queues and JDK6 which allows us to shade the library in netty-common allowing it to stay "zero dependency". Modifications: - Remove copy paste JCTools code and shade the library (dependencies that are shaded should be removed from the <dependencies> section of the generated POM). - Remove usage of OneTimeTask and remove it all together. Result: Less code to maintain and easier to update JCTools and less GC pressure as the queue implementation nt creates so much garbage
224 lines
7.4 KiB
Java
224 lines
7.4 KiB
Java
/*
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* Copyright 2016 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.EventLoop;
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import io.netty.util.internal.PlatformDependent;
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import io.netty.util.internal.UnstableApi;
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import java.net.InetAddress;
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import java.util.ArrayList;
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import java.util.Iterator;
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import java.util.List;
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import java.util.Map;
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import java.util.concurrent.ConcurrentMap;
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import java.util.concurrent.TimeUnit;
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import static io.netty.util.internal.ObjectUtil.checkNotNull;
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import static io.netty.util.internal.ObjectUtil.checkPositiveOrZero;
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/**
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* Default implementation of {@link DnsCache}, backed by a {@link ConcurrentMap}.
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*/
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@UnstableApi
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public class DefaultDnsCache implements DnsCache {
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private final ConcurrentMap<String, List<DnsCacheEntry>> resolveCache = PlatformDependent.newConcurrentHashMap();
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private final int minTtl;
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private final int maxTtl;
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private final int negativeTtl;
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/**
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* Create a cache that respects the TTL returned by the DNS server
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* and doesn't cache negative responses.
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*/
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public DefaultDnsCache() {
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this(0, Integer.MAX_VALUE, 0);
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}
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/**
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* Create a cache.
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* @param minTtl the minimum TTL
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* @param maxTtl the maximum TTL
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* @param negativeTtl the TTL for failed queries
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*/
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public DefaultDnsCache(int minTtl, int maxTtl, int negativeTtl) {
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this.minTtl = checkPositiveOrZero(minTtl, "minTtl");
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this.maxTtl = checkPositiveOrZero(maxTtl, "maxTtl");
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if (minTtl > maxTtl) {
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throw new IllegalArgumentException(
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"minTtl: " + minTtl + ", maxTtl: " + maxTtl + " (expected: 0 <= minTtl <= maxTtl)");
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}
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this.negativeTtl = checkPositiveOrZero(negativeTtl, "negativeTtl");
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}
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/**
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* Returns the minimum TTL of the cached DNS resource records (in seconds).
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*
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* @see #maxTtl()
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*/
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public int minTtl() {
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return minTtl;
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}
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/**
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* Returns the maximum TTL of the cached DNS resource records (in seconds).
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*
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* @see #minTtl()
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*/
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public int maxTtl() {
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return maxTtl;
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}
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/**
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* Returns the TTL of the cache for the failed DNS queries (in seconds). The default value is {@code 0}, which
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* disables the cache for negative results.
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*/
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public int negativeTtl() {
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return negativeTtl;
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}
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@Override
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public void clear() {
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for (Iterator<Map.Entry<String, List<DnsCacheEntry>>> i = resolveCache.entrySet().iterator(); i.hasNext();) {
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final Map.Entry<String, List<DnsCacheEntry>> e = i.next();
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i.remove();
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cancelExpiration(e.getValue());
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}
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}
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@Override
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public boolean clear(String hostname) {
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checkNotNull(hostname, "hostname");
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boolean removed = false;
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for (Iterator<Map.Entry<String, List<DnsCacheEntry>>> i = resolveCache.entrySet().iterator(); i.hasNext();) {
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final Map.Entry<String, List<DnsCacheEntry>> e = i.next();
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if (e.getKey().equals(hostname)) {
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i.remove();
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cancelExpiration(e.getValue());
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removed = true;
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}
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}
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return removed;
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}
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@Override
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public List<DnsCacheEntry> get(String hostname) {
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checkNotNull(hostname, "hostname");
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return resolveCache.get(hostname);
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}
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private List<DnsCacheEntry> cachedEntries(String hostname) {
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List<DnsCacheEntry> oldEntries = resolveCache.get(hostname);
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final List<DnsCacheEntry> entries;
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if (oldEntries == null) {
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List<DnsCacheEntry> newEntries = new ArrayList<DnsCacheEntry>(8);
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oldEntries = resolveCache.putIfAbsent(hostname, newEntries);
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entries = oldEntries != null? oldEntries : newEntries;
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} else {
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entries = oldEntries;
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}
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return entries;
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}
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@Override
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public void cache(String hostname, InetAddress address, long originalTtl, EventLoop loop) {
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if (maxTtl == 0) {
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return;
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}
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checkNotNull(hostname, "hostname");
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checkNotNull(address, "address");
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checkNotNull(loop, "loop");
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final int ttl = Math.max(minTtl, (int) Math.min(maxTtl, originalTtl));
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final List<DnsCacheEntry> entries = cachedEntries(hostname);
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final DnsCacheEntry e = new DnsCacheEntry(hostname, address);
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synchronized (entries) {
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if (!entries.isEmpty()) {
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final DnsCacheEntry firstEntry = entries.get(0);
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if (firstEntry.cause() != null) {
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assert entries.size() == 1;
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firstEntry.cancelExpiration();
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entries.clear();
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}
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}
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entries.add(e);
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}
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scheduleCacheExpiration(entries, e, ttl, loop);
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}
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@Override
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public void cache(String hostname, Throwable cause, EventLoop loop) {
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if (negativeTtl == 0) {
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return;
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}
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checkNotNull(hostname, "hostname");
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checkNotNull(cause, "cause");
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checkNotNull(loop, "loop");
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final List<DnsCacheEntry> entries = cachedEntries(hostname);
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final DnsCacheEntry e = new DnsCacheEntry(hostname, cause);
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synchronized (entries) {
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final int numEntries = entries.size();
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for (int i = 0; i < numEntries; i ++) {
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entries.get(i).cancelExpiration();
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}
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entries.clear();
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entries.add(e);
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}
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scheduleCacheExpiration(entries, e, negativeTtl, loop);
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}
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private static void cancelExpiration(List<DnsCacheEntry> entries) {
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final int numEntries = entries.size();
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for (int i = 0; i < numEntries; i++) {
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entries.get(i).cancelExpiration();
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}
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}
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private void scheduleCacheExpiration(final List<DnsCacheEntry> entries,
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final DnsCacheEntry e,
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int ttl,
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EventLoop loop) {
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e.scheduleExpiration(loop, new Runnable() {
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@Override
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public void run() {
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synchronized (entries) {
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entries.remove(e);
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if (entries.isEmpty()) {
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resolveCache.remove(e.hostname());
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}
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}
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}
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}, ttl, TimeUnit.SECONDS);
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}
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@Override
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public String toString() {
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return new StringBuilder()
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.append("DefaultDnsCache(minTtl=")
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.append(minTtl).append(", maxTtl=")
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.append(maxTtl).append(", negativeTtl=")
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.append(negativeTtl).append(", cached resolved hostname=")
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.append(resolveCache.size()).append(")")
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.toString();
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}
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}
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