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package com.unboundid.directory.sdk.examples;
import java.util.Arrays;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.concurrent.atomic.AtomicLong;
import com.unboundid.directory.sdk.common.operation.AddRequest;
import com.unboundid.directory.sdk.common.types.OperationContext;
import com.unboundid.directory.sdk.proxy.api.PlacementAlgorithm;
import com.unboundid.directory.sdk.proxy.config.PlacementAlgorithmConfig;
import com.unboundid.directory.sdk.proxy.types.BackendSet;
import com.unboundid.directory.sdk.proxy.types.ProxyServerContext;
import com.unboundid.ldap.sdk.Attribute;
import com.unboundid.ldap.sdk.LDAPException;
import com.unboundid.ldap.sdk.ResultCode;
import com.unboundid.util.args.ArgumentException;
import com.unboundid.util.args.ArgumentParser;
import com.unboundid.util.args.IntegerArgument;
import com.unboundid.util.args.StringArgument;
/**
* This class provides a simple example of a placement algorithm which sends
* entries to different backend sets based on a hash generated from the value of
* a specified attribute. If an entry has multiple values for the specified
* attribute, then only the first value will be used. If an entry does not
* have the specified attribute, then a simple round-robin distribution will be
* used.
* <BR><BR>
* It takes the following configuration arguments:
* <UL>
* <LI>attribute-name -- The name of the attribute from which to generate the
* hash.</LI>
* <LI>max-characters -- The maximum number of characters to use from the
* value when generating the hash. A value of zero indicates that all
* characters in the value should be used.</LI>
* </UL>
*/
public final class ExamplePlacementAlgorithm
extends PlacementAlgorithm
{
/**
* The name of the argument that will be used to specify the name of the
* attribute for which to generate the hash.
*/
private static final String ARG_NAME_ATTR = "attribute-name";
/**
* The name of the argument that will be used to specify the maximum number of
* characters to use to generate the hash.
*/
private static final String ARG_NAME_MAX_CHARS = "max-characters";
// A counter that will be used to select backend sets for entries that don't
// contain the target attribute.
private final AtomicLong roundRobinCounter;
// The maximum number of characters to use in the hash.
private volatile int maxChars;
// The list of backend sets currently in use.
private volatile List<BackendSet> backendSets;
// The server context for the server in which this extension is running.
private ProxyServerContext serverContext;
// The name of the attribute to use to generate the hash.
private volatile String attributeName;
/**
* Creates a new instance of this placement algorithm. All placement
* algorithm implementations must include a default constructor, but any
* initialization should generally be done in the
* {@code initializePlacementAlgorithm} method.
*/
public ExamplePlacementAlgorithm()
{
roundRobinCounter = new AtomicLong(0L);
}
/**
* Retrieves a human-readable name for this extension.
*
* @return A human-readable name for this extension.
*/
@Override()
public String getExtensionName()
{
return "Example Placement Algorithm";
}
/**
* Retrieves a human-readable description for this extension. Each element
* of the array that is returned will be considered a separate paragraph in
* generated documentation.
*
* @return A human-readable description for this extension, or {@code null}
* or an empty array if no description should be available.
*/
@Override()
public String[] getExtensionDescription()
{
return new String[]
{
"This placement algorithm serves an example that may be used to " +
"demonstrate the process for creating a third-party placement " +
"algorithm. It will generate a hash from the first value of a " +
"specified attribute and will use that to select which backend " +
"set should be used to hold the associated entry."
};
}
/**
* Updates the provided argument parser to define any configuration arguments
* which may be used by this placement algorithm. The argument parser may
* also be updated to define relationships between arguments (e.g., to specify
* required, exclusive, or dependent argument sets).
*
* @param parser The argument parser to be updated with the configuration
* arguments which may be used by this placement algorithm.
*
* @throws ArgumentException If a problem is encountered while updating the
* provided argument parser.
*/
@Override()
public void defineConfigArguments(final ArgumentParser parser)
throws ArgumentException
{
// Add an argument that allows you to specify the attribute name.
Character shortIdentifier = null;
String longIdentifier = ARG_NAME_ATTR;
boolean required = true;
int maxOccurrences = 1;
String placeholder = "{attr}";
String description = "The name of the attribute whose value " +
"be used to generate a hash for use when selecting the backend set.";
parser.addArgument(new StringArgument(shortIdentifier, longIdentifier,
required, maxOccurrences, placeholder, description));
// Add an argument that allows you to specify the maximum number of
// characters to use when generating the hash.
shortIdentifier = null;
longIdentifier = ARG_NAME_MAX_CHARS;
required = true;
maxOccurrences = 1;
placeholder = "{value}";
description = "The maximum number of characters to use when " +
"generating the hash. A value of zero indicates that the entire " +
"value should be used.";
int lowerBound = 0;
int upperBound = Integer.MAX_VALUE;
int defaultValue = 0;
parser.addArgument(new IntegerArgument(shortIdentifier, longIdentifier,
required, maxOccurrences, placeholder, description, lowerBound,
upperBound, defaultValue));
}
/**
* Initializes this placement algorithm.
*
* @param serverContext A handle to the server context for the server in
* which this extension is running.
* @param config The general configuration for this placement
* algorithm.
* @param parser The argument parser which has been initialized
* from the configuration for this placement
* algorithm.
* @param balancingBaseDN The balancing base DN for the associated
* entry-balancing request processor.
* @param backendSets The list of backend sets that will be used with
* the entry-balancing request processor.
*
* @throws LDAPException If a problem occurs while initializing this
* placement algorithm.
*/
@Override()
public void initializePlacementAlgorithm(
final ProxyServerContext serverContext,
final PlacementAlgorithmConfig config,
final ArgumentParser parser,
final String balancingBaseDN,
final List<BackendSet> backendSets)
throws LDAPException
{
serverContext.debugInfo("Beginning placement algorithm initialization");
this.serverContext = serverContext;
this.backendSets = backendSets;
// Get the target attribute name.
final StringArgument attrArg =
(StringArgument) parser.getNamedArgument(ARG_NAME_ATTR);
attributeName = attrArg.getValue();
// Get the maximum number of characters to use from the value.
final IntegerArgument maxCharsArg =
(IntegerArgument) parser.getNamedArgument(ARG_NAME_MAX_CHARS);
maxChars = maxCharsArg.getValue();
}
/**
* Indicates whether the configuration contained in the provided argument
* parser represents a valid configuration for this extension.
*
* @param config The general configuration for this placement
* algorithm.
* @param parser The argument parser which has been initialized
* with the proposed configuration.
* @param unacceptableReasons A list that can be updated with reasons that
* the proposed configuration is not acceptable.
*
* @return {@code true} if the proposed configuration is acceptable, or
* {@code false} if not.
*/
@Override()
public boolean isConfigurationAcceptable(
final PlacementAlgorithmConfig config,
final ArgumentParser parser,
final List<String> unacceptableReasons)
{
// No special validation is required.
return true;
}
/**
* Attempts to apply the configuration contained in the provided argument
* parser.
*
* @param config The general configuration for this placement
* algorithm.
* @param parser The argument parser which has been
* initialized with the new configuration.
* @param adminActionsRequired A list that can be updated with information
* about any administrative actions that may be
* required before one or more of the
* configuration changes will be applied.
* @param messages A list that can be updated with information
* about the result of applying the new
* configuration.
*
* @return A result code that provides information about the result of
* attempting to apply the configuration change.
*/
@Override()
public ResultCode applyConfiguration(final PlacementAlgorithmConfig config,
final ArgumentParser parser,
final List<String> adminActionsRequired,
final List<String> messages)
{
// Get the new target attribute name.
final StringArgument attrArg =
(StringArgument) parser.getNamedArgument(ARG_NAME_ATTR);
final String newAttr = attrArg.getValue();
// Get the new maximum number of characters to use from the value.
final IntegerArgument maxCharsArg =
(IntegerArgument) parser.getNamedArgument(ARG_NAME_MAX_CHARS);
final int newMax = maxCharsArg.getValue();
attributeName = newAttr;
maxChars = newMax;
return ResultCode.SUCCESS;
}
/**
* Performs any cleanup which may be necessary when this placement algorithm
* is to be taken out of service.
*/
@Override()
public void finalizePlacementAlgorithm()
{
// No finalization is required.
}
/**
* Adapts to a change in the backend sets configured for use with the
* associated entry-balancing request processor.
*
* @param balancingBaseDN The updated balancing base DN for the associated
* entry-balancing request processor.
* @param backendSets The updated list of backend sets for the
* associated entry-balancing request processor.
*/
@Override()
public void applyBalancingConfigurationChange(final String balancingBaseDN,
final List<BackendSet> backendSets)
{
this.backendSets = backendSets;
}
/**
* Determines the backend set that should be used to process the specified
* add operation.
*
* @param operationContext The operation context for the add operation
* to be processed.
* @param addRequest The add request being processed.
*
* @return The backend set in which the add should be processed, or
* {@code null} if there is no appropriate backend set.
*/
@Override()
public BackendSet selectBackendSet(final OperationContext operationContext,
final AddRequest addRequest)
{
// Create a local copy of the configuration in case it changes while this
// method is running.
final int max = maxChars;
final List<BackendSet> sets = backendSets;
final String attr = attributeName;
// Get the target attribute from the entry to be added. Find the first
// value and use it to make the determination.
final List<Attribute> attrList = addRequest.getEntry().getAttribute(attr);
if (attrList != null)
{
for (final Attribute a : attrList)
{
final String value = a.getValue();
if (value != null)
{
final String s;
if ((max == 0) || (max <= value.length()))
{
s = value;
}
else
{
s = value.substring(0, max);
}
final int slot = (s.hashCode() % sets.size());
return sets.get(slot);
}
}
}
// If we've gotten here, then the entry doesn't have a value for the
// specified attribute, so we should use the round-robin counter.
final int slot =
(int) (roundRobinCounter.getAndIncrement() % sets.size());
return sets.get(slot);
}
/**
* Retrieves a map containing examples of configurations that may be used for
* this extension. The map key should be a list of sample arguments, and the
* corresponding value should be a description of the behavior that will be
* exhibited by the extension when used with that configuration.
*
* @return A map containing examples of configurations that may be used for
* this extension. It may be {@code null} or empty if there should
* not be any example argument sets.
*/
@Override()
public Map<List<String>,String> getExamplesArgumentSets()
{
final LinkedHashMap<List<String>,String> exampleMap =
new LinkedHashMap<List<String>,String>(1);
exampleMap.put(
Arrays.asList(
ARG_NAME_ATTR + "=cn",
ARG_NAME_MAX_CHARS + "=10"),
"Select the backend set to use for add operations based on a hash " +
"of up to the first 10 characters of the first value of the " +
"cn attribute.");
return exampleMap;
}
/**
* Appends a string representation of this LDAP health check to the provided
* buffer.
*
* @param buffer The buffer to which the string representation should be
* appended.
*/
@Override()
public void toString(final StringBuilder buffer)
{
buffer.append("ExamplePlacementAlgorithm(attributeName='");
buffer.append(attributeName);
buffer.append("', maxChars=");
buffer.append(maxChars);
buffer.append(')');
}
}
