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/*
* Copyright 2014-2017 UnboundID Corp.
* All Rights Reserved.
*/
/*
* Copyright (C) 2014-2017 UnboundID Corp.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License (GPLv2 only)
* or the terms of the GNU Lesser General Public License (LGPLv2.1 only)
* as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, see .
*/
package com.unboundid.ldap.sdk;
import java.net.InetAddress;
import java.net.UnknownHostException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Hashtable;
import java.util.List;
import java.util.Map;
import java.util.Properties;
import java.util.StringTokenizer;
import java.util.concurrent.atomic.AtomicLong;
import java.util.concurrent.atomic.AtomicReference;
import javax.naming.Context;
import javax.naming.NamingEnumeration;
import javax.naming.directory.Attribute;
import javax.naming.directory.Attributes;
import javax.naming.directory.InitialDirContext;
import javax.net.SocketFactory;
import com.unboundid.util.Debug;
import com.unboundid.util.NotMutable;
import com.unboundid.util.ObjectPair;
import com.unboundid.util.ThreadLocalRandom;
import com.unboundid.util.ThreadSafety;
import com.unboundid.util.ThreadSafetyLevel;
import com.unboundid.util.Validator;
import static com.unboundid.ldap.sdk.LDAPMessages.*;
/**
* This class provides a server set implementation that handles the case in
* which a given host name may resolve to multiple IP addresses. Note that
* while a setup like this is typically referred to as "round-robin DNS", this
* server set implementation does not strictly require DNS (as names may be
* resolved through alternate mechanisms like a hosts file or an alternate name
* service), and it does not strictly require round-robin use of those addresses
* (as alternate ordering mechanisms, like randomized or failover, may be used).
*
*
Example
* The following example demonstrates the process for creating a round-robin DNS
* server set for the case in which the hostname "directory.example.com" may be
* associated with multiple IP addresses, and the LDAP SDK should attempt to use
* them in a round robin manner.
*
* // Define a number of variables that will be used by the server set.
* String hostname = "directory.example.com";
* int port = 389;
* AddressSelectionMode selectionMode =
* AddressSelectionMode.ROUND_ROBIN;
* long cacheTimeoutMillis = 3600000L; // 1 hour
* String providerURL = "dns:"; // Default DNS config.
* SocketFactory socketFactory = null; // Default socket factory.
* LDAPConnectionOptions connectionOptions = null; // Default options.
*
* // Create the server set using the settings defined above.
* RoundRobinDNSServerSet serverSet = new RoundRobinDNSServerSet(hostname,
* port, selectionMode, cacheTimeoutMillis, providerURL, socketFactory,
* connectionOptions);
*
* // Verify that we can establish a single connection using the server set.
* LDAPConnection connection = serverSet.getConnection();
* RootDSE rootDSEFromConnection = connection.getRootDSE();
* connection.close();
*
* // Verify that we can establish a connection pool using the server set.
* SimpleBindRequest bindRequest =
* new SimpleBindRequest("uid=pool.user,dc=example,dc=com", "password");
* LDAPConnectionPool pool =
* new LDAPConnectionPool(serverSet, bindRequest, 10);
* RootDSE rootDSEFromPool = pool.getRootDSE();
* pool.close();
*
*/
@NotMutable()
@ThreadSafety(level=ThreadSafetyLevel.COMPLETELY_THREADSAFE)
public final class RoundRobinDNSServerSet
extends ServerSet
{
/**
* The name of a system property that can be used to specify a comma-delimited
* list of IP addresses to use if resolution fails. This is intended
* primarily for testing purposes.
*/
static final String PROPERTY_DEFAULT_ADDRESSES =
RoundRobinDNSServerSet.class.getName() + ".defaultAddresses";
/**
* An enum that defines the modes that may be used to select the order in
* which addresses should be used in attempts to establish connections.
*/
public enum AddressSelectionMode
{
/**
* The address selection mode that will cause addresses to be consistently
* attempted in the order they are retrieved from the name service.
*/
FAILOVER,
/**
* The address selection mode that will cause the order of addresses to be
* randomized for each attempt.
*/
RANDOM,
/**
* The address selection mode that will cause connection attempts to be made
* in a round-robin order.
*/
ROUND_ROBIN,
}
// The address selection mode that should be used if the provided hostname
// resolves to multiple addresses.
private final AddressSelectionMode selectionMode;
// A counter that will be used to handle round-robin ordering.
private final AtomicLong roundRobinCounter;
// A reference to an object that combines the resolved addresses with a
// timestamp indicating when the value should no longer be trusted.
private final AtomicReference>
resolvedAddressesWithTimeout;
// The properties that will be used to initialize the JNDI context, if any.
private final Hashtable jndiProperties;
// The port number for the target server.
private final int port;
// The set of connection options to use for new connections.
private final LDAPConnectionOptions connectionOptions;
// The maximum length of time, in milliseconds, to cache resolved addresses.
private final long cacheTimeoutMillis;
// The socket factory to use to establish connections.
private final SocketFactory socketFactory;
// The hostname to be resolved.
private final String hostname;
// The provider URL to use to resolve names, if any.
private final String providerURL;
// The DNS record types that will be used to obtain the IP addresses for the
// specified hostname.
private final String[] dnsRecordTypes;
/**
* Creates a new round-robin DNS server set with the provided information.
*
* @param hostname The hostname to be resolved to one or more
* addresses. It must not be {@code null}.
* @param port The port to use to connect to the server. Note
* that even if the provided hostname resolves to
* multiple addresses, the same port must be used
* for all addresses.
* @param selectionMode The selection mode that should be used if the
* hostname resolves to multiple addresses. It
* must not be {@code null}.
* @param cacheTimeoutMillis The maximum length of time in milliseconds to
* cache addresses resolved from the provided
* hostname. Caching resolved addresses can
* result in better performance and can reduce the
* number of requests to the name service. A
* that is less than or equal to zero indicates
* that no caching should be used.
* @param providerURL The JNDI provider URL that should be used when
* communicating with the DNS server. If this is
* {@code null}, then the underlying system's
* name service mechanism will be used (which may
* make use of other services instead of or in
* addition to DNS). If this is non-{@code null},
* then only DNS will be used to perform the name
* resolution. A value of "dns:" indicates that
* the underlying system's DNS configuration
* should be used.
* @param socketFactory The socket factory to use to establish the
* connections. It may be {@code null} if the
* JVM-default socket factory should be used.
* @param connectionOptions The set of connection options that should be
* used for the connections. It may be
* {@code null} if a default set of connection
* options should be used.
*/
public RoundRobinDNSServerSet(final String hostname, final int port,
final AddressSelectionMode selectionMode,
final long cacheTimeoutMillis,
final String providerURL,
final SocketFactory socketFactory,
final LDAPConnectionOptions connectionOptions)
{
this(hostname, port, selectionMode, cacheTimeoutMillis, providerURL,
null, null, socketFactory, connectionOptions);
}
/**
* Creates a new round-robin DNS server set with the provided information.
*
* @param hostname The hostname to be resolved to one or more
* addresses. It must not be {@code null}.
* @param port The port to use to connect to the server. Note
* that even if the provided hostname resolves to
* multiple addresses, the same port must be used
* for all addresses.
* @param selectionMode The selection mode that should be used if the
* hostname resolves to multiple addresses. It
* must not be {@code null}.
* @param cacheTimeoutMillis The maximum length of time in milliseconds to
* cache addresses resolved from the provided
* hostname. Caching resolved addresses can
* result in better performance and can reduce the
* number of requests to the name service. A
* that is less than or equal to zero indicates
* that no caching should be used.
* @param providerURL The JNDI provider URL that should be used when
* communicating with the DNS server.If both
* {@code providerURL} and {@code jndiProperties}
* are {@code null}, then then JNDI will not be
* used to interact with DNS and the hostname
* resolution will be performed via the underlying
* system's name service mechanism (which may make
* use of other services instead of or in addition
* to DNS).. If this is non-{@code null}, then
* only DNS will be used to perform the name
* resolution. A value of "dns:" indicates that
* the underlying system's DNS configuration
* should be used.
* @param jndiProperties A set of JNDI-related properties that should be
* be used when initializing the context for
* interacting with the DNS server via JNDI. If
* both {@code providerURL} and
* {@code jndiProperties} are {@code null}, then
* then JNDI will not be used to interact with
* DNS and the hostname resolution will be
* performed via the underlying system's name
* service mechanism (which may make use of other
* services instead of or in addition to DNS). If
* {@code providerURL} is {@code null} and
* {@code jndiProperties} is non-{@code null},
* then the provided properties must specify the
* URL.
* @param dnsRecordTypes Specifies the types of DNS records that will be
* used to obtain the addresses for the specified
* hostname. This will only be used if at least
* one of {@code providerURL} and
* {@code jndiProperties} is non-{@code null}. If
* this is {@code null} or empty, then a default
* record type of "A" (indicating IPv4 addresses)
* will be used.
* @param socketFactory The socket factory to use to establish the
* connections. It may be {@code null} if the
* JVM-default socket factory should be used.
* @param connectionOptions The set of connection options that should be
* used for the connections. It may be
* {@code null} if a default set of connection
* options should be used.
*/
public RoundRobinDNSServerSet(final String hostname, final int port,
final AddressSelectionMode selectionMode,
final long cacheTimeoutMillis,
final String providerURL,
final Properties jndiProperties,
final String[] dnsRecordTypes,
final SocketFactory socketFactory,
final LDAPConnectionOptions connectionOptions)
{
Validator.ensureNotNull(hostname);
Validator.ensureTrue((port >= 1) && (port <= 65535));
Validator.ensureNotNull(selectionMode);
this.hostname = hostname;
this.port = port;
this.selectionMode = selectionMode;
this.providerURL = providerURL;
if (jndiProperties == null)
{
if (providerURL == null)
{
this.jndiProperties = null;
}
else
{
this.jndiProperties = new Hashtable(2);
this.jndiProperties.put(Context.INITIAL_CONTEXT_FACTORY,
"com.sun.jndi.dns.DnsContextFactory");
this.jndiProperties.put(Context.PROVIDER_URL, providerURL);
}
}
else
{
this.jndiProperties =
new Hashtable(jndiProperties.size()+2);
for (final Map.Entry e : jndiProperties.entrySet())
{
this.jndiProperties.put(String.valueOf(e.getKey()),
String.valueOf(e.getValue()));
}
if (! this.jndiProperties.containsKey(Context.INITIAL_CONTEXT_FACTORY))
{
this.jndiProperties.put(Context.INITIAL_CONTEXT_FACTORY,
"com.sun.jndi.dns.DnsContextFactory");
}
if ((! this.jndiProperties.containsKey(Context.PROVIDER_URL)) &&
(providerURL != null))
{
this.jndiProperties.put(Context.PROVIDER_URL, providerURL);
}
}
if (dnsRecordTypes == null)
{
this.dnsRecordTypes = new String[] { "A" };
}
else
{
this.dnsRecordTypes = dnsRecordTypes;
}
if (cacheTimeoutMillis > 0L)
{
this.cacheTimeoutMillis = cacheTimeoutMillis;
}
else
{
this.cacheTimeoutMillis = 0L;
}
if (socketFactory == null)
{
this.socketFactory = SocketFactory.getDefault();
}
else
{
this.socketFactory = socketFactory;
}
if (connectionOptions == null)
{
this.connectionOptions = new LDAPConnectionOptions();
}
else
{
this.connectionOptions = connectionOptions;
}
roundRobinCounter = new AtomicLong(0L);
resolvedAddressesWithTimeout =
new AtomicReference>();
}
/**
* Retrieves the hostname to be resolved.
*
* @return The hostname to be resolved.
*/
public String getHostname()
{
return hostname;
}
/**
* Retrieves the port to use to connect to the server.
*
* @return The port to use to connect to the server.
*/
public int getPort()
{
return port;
}
/**
* Retrieves the address selection mode that should be used if the provided
* hostname resolves to multiple addresses.
*
* @return The address selection
*/
public AddressSelectionMode getAddressSelectionMode()
{
return selectionMode;
}
/**
* Retrieves the length of time in milliseconds that resolved addresses may be
* cached.
*
* @return The length of time in milliseconds that resolved addresses may be
* cached, or zero if no caching should be performed.
*/
public long getCacheTimeoutMillis()
{
return cacheTimeoutMillis;
}
/**
* Retrieves the provider URL that should be used when interacting with DNS to
* resolve the hostname to its corresponding addresses.
*
* @return The provider URL that should be used when interacting with DNS to
* resolve the hostname to its corresponding addresses, or
* {@code null} if the system's configured naming service should be
* used.
*/
public String getProviderURL()
{
return providerURL;
}
/**
* Retrieves an unmodifiable map of properties that will be used to initialize
* the JNDI context used to interact with DNS. Note that the map returned
* will reflect the actual properties that will be used, and may not exactly
* match the properties provided when creating this server set.
*
* @return An unmodifiable map of properties that will be used to initialize
* the JNDI context used to interact with DNS, or {@code null} if
* JNDI will nto be used to interact with DNS.
*/
public Map getJNDIProperties()
{
if (jndiProperties == null)
{
return null;
}
else
{
return Collections.unmodifiableMap(jndiProperties);
}
}
/**
* Retrieves an array of record types that will be requested if JNDI will be
* used to interact with DNS.
*
* @return An array of record types that will be requested if JNDI will be
* used to interact with DNS.
*/
public String[] getDNSRecordTypes()
{
return dnsRecordTypes;
}
/**
* Retrieves the socket factory that will be used to establish connections.
* This will not be {@code null}, even if no socket factory was provided when
* the server set was created.
*
* @return The socket factory that will be used to establish connections.
*/
public SocketFactory getSocketFactory()
{
return socketFactory;
}
/**
* Retrieves the set of connection options that will be used for underlying
* connections. This will not be {@code null}, even if no connection options
* object was provided when the server set was created.
*
* @return The set of connection options that will be used for underlying
* connections.
*/
public LDAPConnectionOptions getConnectionOptions()
{
return connectionOptions;
}
/**
* {@inheritDoc}
*/
@Override()
public LDAPConnection getConnection()
throws LDAPException
{
return getConnection(null);
}
/**
* {@inheritDoc}
*/
@Override()
public synchronized LDAPConnection getConnection(
final LDAPConnectionPoolHealthCheck healthCheck)
throws LDAPException
{
LDAPException firstException = null;
final LDAPConnection conn =
new LDAPConnection(socketFactory, connectionOptions);
for (final InetAddress a : orderAddresses(resolveHostname()))
{
boolean close = true;
try
{
conn.connect(hostname, a, port,
connectionOptions.getConnectTimeoutMillis());
if (healthCheck != null)
{
healthCheck.ensureNewConnectionValid(conn);
}
close = false;
return conn;
}
catch (final LDAPException le)
{
Debug.debugException(le);
if (firstException == null)
{
firstException = le;
}
}
finally
{
if (close)
{
conn.close();
}
}
}
throw firstException;
}
/**
* Resolve the hostname to its corresponding addresses.
*
* @return The addresses resolved from the hostname.
*
* @throws LDAPException If
*/
InetAddress[] resolveHostname()
throws LDAPException
{
// First, see if we can use the cached addresses.
final ObjectPair pair =
resolvedAddressesWithTimeout.get();
if (pair != null)
{
if (pair.getSecond() <= System.currentTimeMillis())
{
return pair.getFirst();
}
}
// Try to resolve the address.
InetAddress[] addresses = null;
try
{
if (jndiProperties == null)
{
addresses = InetAddress.getAllByName(hostname);
}
else
{
Attributes attributes = null;
final InitialDirContext context = new InitialDirContext(jndiProperties);
try
{
attributes = context.getAttributes(hostname, dnsRecordTypes);
}
finally
{
context.close();
}
if (attributes != null)
{
final ArrayList addressList =
new ArrayList(10);
for (final String recordType : dnsRecordTypes)
{
final Attribute a = attributes.get(recordType);
if (a != null)
{
final NamingEnumeration values = a.getAll();
while (values.hasMore())
{
final Object value = values.next();
addressList.add(getInetAddressForIP(String.valueOf(value)));
}
}
}
if (! addressList.isEmpty())
{
addresses = new InetAddress[addressList.size()];
addressList.toArray(addresses);
}
}
}
}
catch (final Exception e)
{
Debug.debugException(e);
addresses = getDefaultAddresses();
}
// If we were able to resolve the hostname, then cache and return the
// resolved addresses.
if ((addresses != null) && (addresses.length > 0))
{
final long timeoutTime;
if (cacheTimeoutMillis > 0L)
{
timeoutTime = System.currentTimeMillis() + cacheTimeoutMillis;
}
else
{
timeoutTime = System.currentTimeMillis() - 1L;
}
resolvedAddressesWithTimeout.set(new ObjectPair(
addresses, timeoutTime));
return addresses;
}
// If we've gotten here, then we couldn't resolve the hostname. If we have
// cached addresses, then use them even though the timeout has expired
// because that's better than nothing.
if (pair != null)
{
return pair.getFirst();
}
throw new LDAPException(ResultCode.CONNECT_ERROR,
ERR_ROUND_ROBIN_DNS_SERVER_SET_CANNOT_RESOLVE.get(hostname));
}
/**
* Orders the provided array of InetAddress objects to reflect the order in
* which the addresses should be used to try to create a new connection.
*
* @param addresses The array of addresses to be ordered.
*
* @return A list containing the ordered addresses.
*/
List orderAddresses(final InetAddress[] addresses)
{
final ArrayList l =
new ArrayList(addresses.length);
switch (selectionMode)
{
case RANDOM:
l.addAll(Arrays.asList(addresses));
Collections.shuffle(l, ThreadLocalRandom.get());
break;
case ROUND_ROBIN:
final int index =
(int) (roundRobinCounter.getAndIncrement() % addresses.length);
for (int i=index; i < addresses.length; i++)
{
l.add(addresses[i]);
}
for (int i=0; i < index; i++)
{
l.add(addresses[i]);
}
break;
case FAILOVER:
default:
// We'll use the addresses in the same order we originally got them.
l.addAll(Arrays.asList(addresses));
break;
}
return l;
}
/**
* Retrieves a default set of addresses that may be used for testing.
*
* @return A default set of addresses that may be used for testing.
*/
InetAddress[] getDefaultAddresses()
{
final String defaultAddrsStr =
System.getProperty(PROPERTY_DEFAULT_ADDRESSES);
if (defaultAddrsStr == null)
{
return null;
}
final StringTokenizer tokenizer =
new StringTokenizer(defaultAddrsStr, " ,");
final InetAddress[] addresses = new InetAddress[tokenizer.countTokens()];
for (int i=0; i < addresses.length; i++)
{
try
{
addresses[i] = getInetAddressForIP(tokenizer.nextToken());
}
catch (final Exception e)
{
Debug.debugException(e);
return null;
}
}
return addresses;
}
/**
* Retrieves an InetAddress object with the configured hostname and the
* provided IP address.
*
* @param ipAddress The string representation of the IP address to use in
* the returned InetAddress.
*
* @return The created InetAddress.
*
* @throws UnknownHostException If the provided string does not represent a
* valid IPv4 or IPv6 address.
*/
private InetAddress getInetAddressForIP(final String ipAddress)
throws UnknownHostException
{
// We want to create an InetAddress that has the provided hostname and the
// specified IP address. To do that, we need to use
// InetAddress.getByAddress. But that requires the IP address to be
// specified as a byte array, and the easiest way to convert an IP address
// string to a byte array is to use InetAddress.getByName.
final InetAddress byName = InetAddress.getByName(String.valueOf(ipAddress));
return InetAddress.getByAddress(hostname, byName.getAddress());
}
/**
* {@inheritDoc}
*/
@Override()
public void toString(final StringBuilder buffer)
{
buffer.append("RoundRobinDNSServerSet(hostname='");
buffer.append(hostname);
buffer.append("', port=");
buffer.append(port);
buffer.append(", addressSelectionMode=");
buffer.append(selectionMode.name());
buffer.append(", cacheTimeoutMillis=");
buffer.append(cacheTimeoutMillis);
if (providerURL != null)
{
buffer.append(", providerURL='");
buffer.append(providerURL);
buffer.append('\'');
}
buffer.append(')');
}
}
