/*
* Copyright DataStax, Inc.
*
* Licensed 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 com.datastax.oss.driver.internal.core.addresstranslation;
import com.datastax.oss.driver.api.core.addresstranslation.AddressTranslator;
import com.datastax.oss.driver.api.core.context.DriverContext;
import com.datastax.oss.driver.internal.core.util.Loggers;
import com.datastax.oss.driver.shaded.guava.common.annotations.VisibleForTesting;
import edu.umd.cs.findbugs.annotations.NonNull;
import java.net.InetAddress;
import java.net.InetSocketAddress;
import java.util.Enumeration;
import java.util.Hashtable;
import javax.naming.Context;
import javax.naming.NamingEnumeration;
import javax.naming.NamingException;
import javax.naming.directory.Attribute;
import javax.naming.directory.Attributes;
import javax.naming.directory.DirContext;
import javax.naming.directory.InitialDirContext;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
AddressTranslator
implementation for a multi-region EC2 deployment where clients are
also deployed in EC2.
Its distinctive feature is that it translates addresses according to the location of the
Cassandra host:
- addresses in different EC2 regions (than the client) are unchanged;
- addresses in the same EC2 region are translated to private IPs.
This optimizes network costs, because Amazon charges more for communication over public IPs.
Implementation note: this class performs a reverse DNS lookup of the origin address, to find
the domain name of the target instance. Then it performs a forward DNS lookup of the domain name;
the EC2 DNS does the private/public switch automatically based on location.
/**
* {@link AddressTranslator} implementation for a multi-region EC2 deployment <b>where clients are
* also deployed in EC2</b>.
*
* <p>Its distinctive feature is that it translates addresses according to the location of the
* Cassandra host:
*
* <ul>
* <li>addresses in different EC2 regions (than the client) are unchanged;
* <li>addresses in the same EC2 region are <b>translated to private IPs</b>.
* </ul>
*
* This optimizes network costs, because Amazon charges more for communication over public IPs.
*
* <p>Implementation note: this class performs a reverse DNS lookup of the origin address, to find
* the domain name of the target instance. Then it performs a forward DNS lookup of the domain name;
* the EC2 DNS does the private/public switch automatically based on location.
*/
public class Ec2MultiRegionAddressTranslator implements AddressTranslator {
private static final Logger LOG = LoggerFactory.getLogger(Ec2MultiRegionAddressTranslator.class);
private final DirContext ctx;
private final String logPrefix;
public Ec2MultiRegionAddressTranslator(
@SuppressWarnings("unused") @NonNull DriverContext context) {
this.logPrefix = context.getSessionName();
@SuppressWarnings("JdkObsolete")
Hashtable<Object, Object> env = new Hashtable<>();
env.put(Context.INITIAL_CONTEXT_FACTORY, "com.sun.jndi.dns.DnsContextFactory");
try {
ctx = new InitialDirContext(env);
} catch (NamingException e) {
throw new RuntimeException("Could not create translator", e);
}
}
@VisibleForTesting
Ec2MultiRegionAddressTranslator(@NonNull DirContext ctx) {
this.logPrefix = "test";
this.ctx = ctx;
}
@NonNull
@Override
public InetSocketAddress translate(@NonNull InetSocketAddress socketAddress) {
InetAddress address = socketAddress.getAddress();
try {
// InetAddress#getHostName() is supposed to perform a reverse DNS lookup, but for some reason
// it doesn't work within the same EC2 region (it returns the IP address itself).
// We use an alternate implementation:
String domainName = lookupPtrRecord(reverse(address));
if (domainName == null) {
LOG.warn("[{}] Found no domain name for {}, returning it as-is", logPrefix, address);
return socketAddress;
}
InetAddress translatedAddress = InetAddress.getByName(domainName);
LOG.debug("[{}] Resolved {} to {}", logPrefix, address, translatedAddress);
return new InetSocketAddress(translatedAddress, socketAddress.getPort());
} catch (Exception e) {
Loggers.warnWithException(
LOG, "[{}] Error resolving {}, returning it as-is", logPrefix, address, e);
return socketAddress;
}
}
private String lookupPtrRecord(String reversedDomain) throws Exception {
Attributes attrs = ctx.getAttributes(reversedDomain, new String[] {"PTR"});
for (NamingEnumeration ae = attrs.getAll(); ae.hasMoreElements(); ) {
Attribute attr = (Attribute) ae.next();
Enumeration<?> vals = attr.getAll();
if (vals.hasMoreElements()) {
return vals.nextElement().toString();
}
}
return null;
}
@Override
public void close() {
try {
ctx.close();
} catch (NamingException e) {
Loggers.warnWithException(LOG, "Error closing translator", e);
}
}
// Builds the "reversed" domain name in the ARPA domain to perform the reverse lookup
@VisibleForTesting
static String reverse(InetAddress address) {
byte[] bytes = address.getAddress();
if (bytes.length == 4) return reverseIpv4(bytes);
else return reverseIpv6(bytes);
}
private static String reverseIpv4(byte[] bytes) {
StringBuilder builder = new StringBuilder();
for (int i = bytes.length - 1; i >= 0; i--) {
builder.append(bytes[i] & 0xFF).append('.');
}
builder.append("in-addr.arpa");
return builder.toString();
}
private static String reverseIpv6(byte[] bytes) {
StringBuilder builder = new StringBuilder();
for (int i = bytes.length - 1; i >= 0; i--) {
byte b = bytes[i];
int lowNibble = b & 0x0F;
int highNibble = b >> 4 & 0x0F;
builder
.append(Integer.toHexString(lowNibble))
.append('.')
.append(Integer.toHexString(highNibble))
.append('.');
}
builder.append("ip6.arpa");
return builder.toString();
}
}