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Add cache for CNAME mappings resolved during lookup of DNS entries. (n…
…etty#8314) * Add cache for CNAME mappings resolved during lookup of DNS entries. Motivation: If the CNAMEd hostname is backed by load balancing component, typically the final A or AAAA DNS records have small TTL. However, the CNAME record itself is setup with longer TTL. For example: * x.netty.io could be CNAMEd to y.netty.io with TTL of 5 min * A / AAAA records for y.netty.io has a TTL of 0.5 min In current Netty implementation, original hostname is saved in resolved cached with the TTL of final A / AAAA records. When that cache entry expires, Netty recursive resolver sends at least two queries — 1st one to be resolved as CNAME record and the 2nd one to resolve the hostname in CNAME record. If CNAME record was cached, only the 2nd query would be needed most of the time. 1st query would be needed less frequently. Modifications: Add a new CnameCache that will be used to cache CNAMEs and so may reduce queries. Result: Less queries needed when CNAME is used.
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99
resolver-dns/src/main/java/io/netty/resolver/dns/DefaultDnsCnameCache.java
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| @@ -0,0 +1,99 @@ | ||
| /* | ||
| * Copyright 2018 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; | ||
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| import io.netty.channel.EventLoop; | ||
| import io.netty.util.AsciiString; | ||
| import io.netty.util.internal.UnstableApi; | ||
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| import java.util.List; | ||
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| import static io.netty.util.internal.ObjectUtil.*; | ||
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| /** | ||
| * Default implementation of a {@link DnsCnameCache}. | ||
| */ | ||
| @UnstableApi | ||
| public final class DefaultDnsCnameCache implements DnsCnameCache { | ||
| private final int minTtl; | ||
| private final int maxTtl; | ||
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| private final Cache<String> cache = new Cache<String>() { | ||
| @Override | ||
| protected boolean shouldReplaceAll(String entry) { | ||
| // Only one 1:1 mapping is supported as specified in the RFC. | ||
| return true; | ||
| } | ||
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| @Override | ||
| protected boolean equals(String entry, String otherEntry) { | ||
| return AsciiString.contentEqualsIgnoreCase(entry, otherEntry); | ||
| } | ||
| }; | ||
|
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| /** | ||
| * Create a cache that respects the TTL returned by the DNS server. | ||
| */ | ||
| public DefaultDnsCnameCache() { | ||
| this(0, Cache.MAX_SUPPORTED_TTL_SECS); | ||
| } | ||
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| /** | ||
| * Create a cache. | ||
| * | ||
| * @param minTtl the minimum TTL | ||
| * @param maxTtl the maximum TTL | ||
| */ | ||
| public DefaultDnsCnameCache(int minTtl, int maxTtl) { | ||
| this.minTtl = Math.min(Cache.MAX_SUPPORTED_TTL_SECS, checkPositiveOrZero(minTtl, "minTtl")); | ||
| this.maxTtl = Math.min(Cache.MAX_SUPPORTED_TTL_SECS, checkPositive(maxTtl, "maxTtl")); | ||
| if (minTtl > maxTtl) { | ||
| throw new IllegalArgumentException( | ||
| "minTtl: " + minTtl + ", maxTtl: " + maxTtl + " (expected: 0 <= minTtl <= maxTtl)"); | ||
| } | ||
| } | ||
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| @SuppressWarnings("unchecked") | ||
| @Override | ||
| public String get(String hostname) { | ||
| checkNotNull(hostname, "hostname"); | ||
| List<? extends String> cached = cache.get(hostname); | ||
| if (cached == null || cached.isEmpty()) { | ||
| return null; | ||
| } | ||
| // We can never have more then one record. | ||
| return cached.get(0); | ||
| } | ||
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| @Override | ||
| public void cache(String hostname, String cname, long originalTtl, EventLoop loop) { | ||
| checkNotNull(hostname, "hostname"); | ||
| checkNotNull(cname, "cname"); | ||
| checkNotNull(loop, "loop"); | ||
| cache.cache(hostname, cname, Math.max(minTtl, (int) Math.min(maxTtl, originalTtl)), loop); | ||
| } | ||
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| @Override | ||
| public void clear() { | ||
| cache.clear(); | ||
| } | ||
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| @Override | ||
| public boolean clear(String hostname) { | ||
| checkNotNull(hostname, "hostname"); | ||
| return cache.clear(hostname); | ||
| } | ||
| } |
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resolver-dns/src/main/java/io/netty/resolver/dns/DnsCnameCache.java
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,59 @@ | ||
| /* | ||
| * Copyright 2018 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; | ||
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| import io.netty.channel.EventLoop; | ||
| import io.netty.util.internal.UnstableApi; | ||
|
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| /** | ||
| * A cache for {@code CNAME}s. | ||
| */ | ||
| @UnstableApi | ||
| public interface DnsCnameCache { | ||
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| /** | ||
| * Returns the cached cname for the given hostname. | ||
| * | ||
| * @param hostname the hostname | ||
| * @return the cached entries or an {@code null} if none. | ||
| */ | ||
| String get(String hostname); | ||
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| /** | ||
| * Caches a cname entry that should be used for the given hostname. | ||
| * | ||
| * @param hostname the hostname | ||
| * @param cname the cname mapping. | ||
| * @param originalTtl the TTL as returned by the DNS server | ||
| * @param loop the {@link EventLoop} used to register the TTL timeout | ||
| */ | ||
| void cache(String hostname, String cname, long originalTtl, EventLoop loop); | ||
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| /** | ||
| * Clears all cached nameservers. | ||
| * | ||
| * @see #clear(String) | ||
| */ | ||
| void clear(); | ||
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| /** | ||
| * Clears the cached nameservers for the specified hostname. | ||
| * | ||
| * @return {@code true} if and only if there was an entry for the specified host name in the cache and | ||
| * it has been removed by this method | ||
| */ | ||
| boolean clear(String hostname); | ||
| } |
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