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/*
* Copyright 2016 The Netty Project
*
* The Netty Project 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 io.netty.resolver.dns;
import io.netty.channel.EventLoop;
import io.netty.handler.codec.dns.DnsRecord;
import io.netty.util.internal.StringUtil;
import io.netty.util.internal.UnstableApi;
import java.net.InetAddress;
import java.util.Collections;
import java.util.List;
import java.util.concurrent.ConcurrentMap;
import static io.netty.util.internal.ObjectUtil.checkNotNull;
import static io.netty.util.internal.ObjectUtil.checkPositiveOrZero;
/**
* Default implementation of {@link DnsCache}, backed by a {@link ConcurrentMap}.
* If any additional {@link DnsRecord} is used, no caching takes place.
*/
@UnstableApi
public class DefaultDnsCache implements DnsCache {
private final Cache resolveCache = new Cache() {
@Override
protected boolean shouldReplaceAll(DefaultDnsCacheEntry entry) {
return entry.cause() != null;
}
@Override
protected boolean equals(DefaultDnsCacheEntry entry, DefaultDnsCacheEntry otherEntry) {
if (entry.address() != null) {
return entry.address().equals(otherEntry.address());
}
if (otherEntry.address() != null) {
return false;
}
return entry.cause().equals(otherEntry.cause());
}
};
private final int minTtl;
private final int maxTtl;
private final int negativeTtl;
/**
* Create a cache that respects the TTL returned by the DNS server
* and doesn't cache negative responses.
*/
public DefaultDnsCache() {
this(0, Cache.MAX_SUPPORTED_TTL_SECS, 0);
}
/**
* Create a cache.
* @param minTtl the minimum TTL
* @param maxTtl the maximum TTL
* @param negativeTtl the TTL for failed queries
*/
public DefaultDnsCache(int minTtl, int maxTtl, int negativeTtl) {
this.minTtl = Math.min(Cache.MAX_SUPPORTED_TTL_SECS, checkPositiveOrZero(minTtl, "minTtl"));
this.maxTtl = Math.min(Cache.MAX_SUPPORTED_TTL_SECS, checkPositiveOrZero(maxTtl, "maxTtl"));
if (minTtl > maxTtl) {
throw new IllegalArgumentException(
"minTtl: " + minTtl + ", maxTtl: " + maxTtl + " (expected: 0 <= minTtl <= maxTtl)");
}
this.negativeTtl = checkPositiveOrZero(negativeTtl, "negativeTtl");
}
/**
* Returns the minimum TTL of the cached DNS resource records (in seconds).
*
* @see #maxTtl()
*/
public int minTtl() {
return minTtl;
}
/**
* Returns the maximum TTL of the cached DNS resource records (in seconds).
*
* @see #minTtl()
*/
public int maxTtl() {
return maxTtl;
}
/**
* Returns the TTL of the cache for the failed DNS queries (in seconds). The default value is {@code 0}, which
* disables the cache for negative results.
*/
public int negativeTtl() {
return negativeTtl;
}
@Override
public void clear() {
resolveCache.clear();
}
@Override
public boolean clear(String hostname) {
checkNotNull(hostname, "hostname");
return resolveCache.clear(appendDot(hostname));
}
private static boolean emptyAdditionals(DnsRecord[] additionals) {
return additionals == null || additionals.length == 0;
}
@Override
public List get(String hostname, DnsRecord[] additionals) {
checkNotNull(hostname, "hostname");
if (!emptyAdditionals(additionals)) {
return Collections.emptyList();
}
return resolveCache.get(appendDot(hostname));
}
@Override
public DnsCacheEntry cache(String hostname, DnsRecord[] additionals,
InetAddress address, long originalTtl, EventLoop loop) {
checkNotNull(hostname, "hostname");
checkNotNull(address, "address");
checkNotNull(loop, "loop");
DefaultDnsCacheEntry e = new DefaultDnsCacheEntry(hostname, address);
if (maxTtl == 0 || !emptyAdditionals(additionals)) {
return e;
}
resolveCache.cache(appendDot(hostname), e, Math.max(minTtl, (int) Math.min(maxTtl, originalTtl)), loop);
return e;
}
@Override
public DnsCacheEntry cache(String hostname, DnsRecord[] additionals, Throwable cause, EventLoop loop) {
checkNotNull(hostname, "hostname");
checkNotNull(cause, "cause");
checkNotNull(loop, "loop");
DefaultDnsCacheEntry e = new DefaultDnsCacheEntry(hostname, cause);
if (negativeTtl == 0 || !emptyAdditionals(additionals)) {
return e;
}
resolveCache.cache(appendDot(hostname), e, negativeTtl, loop);
return e;
}
@Override
public String toString() {
return new StringBuilder()
.append("DefaultDnsCache(minTtl=")
.append(minTtl).append(", maxTtl=")
.append(maxTtl).append(", negativeTtl=")
.append(negativeTtl).append(", cached resolved hostname=")
.append(resolveCache.size()).append(')')
.toString();
}
private static final class DefaultDnsCacheEntry implements DnsCacheEntry {
private final String hostname;
private final InetAddress address;
private final Throwable cause;
DefaultDnsCacheEntry(String hostname, InetAddress address) {
this.hostname = hostname;
this.address = address;
cause = null;
}
DefaultDnsCacheEntry(String hostname, Throwable cause) {
this.hostname = hostname;
this.cause = cause;
address = null;
}
@Override
public InetAddress address() {
return address;
}
@Override
public Throwable cause() {
return cause;
}
String hostname() {
return hostname;
}
@Override
public String toString() {
if (cause != null) {
return hostname + '/' + cause;
} else {
return address.toString();
}
}
}
private static String appendDot(String hostname) {
return StringUtil.endsWith(hostname, '.') ? hostname : hostname + '.';
}
}
