org.apache.pulsar.common.util.netty.DnsResolverUtil Maven / Gradle / Ivy
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* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF 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 org.apache.pulsar.common.util.netty;
import org.apache.pulsar.shade.io.netty.resolver.dns.DnsNameResolverBuilder;
import java.security.Security;
import java.util.Optional;
import lombok.extern.slf4j.Slf4j;
@Slf4j
public class DnsResolverUtil {
private static final String CACHE_POLICY_PROP = "networkaddress.cache.ttl";
private static final String CACHE_POLICY_PROP_FALLBACK = "sun.net.inetaddr.ttl";
private static final String NEGATIVE_CACHE_POLICY_PROP = "networkaddress.cache.negative.ttl";
private static final String NEGATIVE_CACHE_POLICY_PROP_FALLBACK = "sun.net.inetaddr.negative.ttl";
/* default ttl value from sun.net.InetAddressCachePolicy.DEFAULT_POSITIVE， which is used when no security manager
is used */
private static final int JDK_DEFAULT_TTL = 30;
private static final int MIN_TTL = 0;
private static final int TTL;
private static final int NEGATIVE_TTL;
// default TTL value when JDK setting is "forever" (-1)
private static final int DEFAULT_TTL = 60;
// default negative TTL value when JDK setting is "forever" (-1)
private static final int DEFAULT_NEGATIVE_TTL = 10;
static {
int ttl = DEFAULT_TTL;
int negativeTtl = DEFAULT_NEGATIVE_TTL;
try {
String ttlStr = Security.getProperty(CACHE_POLICY_PROP);
if (ttlStr == null) {
// Compatible with sun.net.inetaddr.ttl settings
ttlStr = System.getProperty(CACHE_POLICY_PROP_FALLBACK);
}
String negativeTtlStr = Security.getProperty(NEGATIVE_CACHE_POLICY_PROP);
if (negativeTtlStr == null) {
// Compatible with sun.net.inetaddr.negative.ttl settings
negativeTtlStr = System.getProperty(NEGATIVE_CACHE_POLICY_PROP_FALLBACK);
}
ttl = Optional.ofNullable(ttlStr)
.map(Integer::decode)
.filter(i -> i > 0)
.orElseGet(() -> {
if (System.getSecurityManager() == null) {
return JDK_DEFAULT_TTL;
}
return DEFAULT_TTL;
});
negativeTtl = Optional.ofNullable(negativeTtlStr)
.map(Integer::decode)
.filter(i -> i >= 0)
.orElse(DEFAULT_NEGATIVE_TTL);
} catch (NumberFormatException e) {
log.warn("Cannot get DNS TTL settings", e);
}
TTL = ttl;
NEGATIVE_TTL = negativeTtl;
}
private DnsResolverUtil() {
// utility class with static methods, prevent instantiation
}
/**
* Configure Netty's {@link DnsNameResolverBuilder}'s ttl and negativeTtl to match the JDK's DNS caching settings.
* If the JDK setting for TTL is forever (-1), the TTL will be set to 60 seconds.
*
* @param dnsNameResolverBuilder The Netty {@link DnsNameResolverBuilder} instance to apply the settings
*/
public static void applyJdkDnsCacheSettings(DnsNameResolverBuilder dnsNameResolverBuilder) {
dnsNameResolverBuilder.ttl(MIN_TTL, TTL);
dnsNameResolverBuilder.negativeTtl(NEGATIVE_TTL);
}
}