com.unboundid.directory.sdk.proxy.api

Class LDAPHealthCheck

java.lang.Object

com.unboundid.directory.sdk.proxy.api.LDAPHealthCheck

All Implemented Interfaces:

Configurable, ExampleUsageProvider, Reconfigurable<LDAPHealthCheckConfig>, UnboundIDExtension

@Extensible
 @DirectoryProxyServerExtension(appliesToLocalContent=false,
                               appliesToRemoteContent=true)
 @ThreadSafety(level=INTERFACE_THREADSAFE)
public abstract class LDAPHealthCheck
extends java.lang.Object
implements UnboundIDExtension, Reconfigurable<LDAPHealthCheckConfig>, ExampleUsageProvider

This class defines an API that must be implemented by extensions which are used to assess the health of backend servers accessed through the Directory Proxy Server. Each health check invocation generates a health check result, which contains the following elements:

• Health Check State -- This indicates the general health state for the backend server. The state may be AVAILABLE (the server is completely suitable for use), DEGRADED (the server should be avoided if there are better servers but may be used if necessary), or UNAVAILABLE (the server should not be used at all).
• Health Check Score -- This provides an integer value between 10 (the best score) and 1 (the worst score) that may help rank servers with the same state. Some load-balancing algorithms (e.g., the health-weighted algorithm) may use this to prefer servers with a higher score over those with a lower score. Servers with a state of UNAVAILABLE will always have a score of zero.
• Messages -- This may optionally provide information about the reason for the state and/or score. This is primarily useful for results indicating that the server is DEGRADED or UNAVAILABLE to provide information about the problem(s) preventing it from being considered AVAILABLE.

LDAP health checks may be invoked in two ways. They will be invoked on a regular basis to periodically re-assess the health of each backend server, but they may also be invoked after a failed operation in order to more quickly detect a problem that should cause the server to be transitioned to a less-available state. The server will ensure that no more than one health check is in progress at a time for a given server in order to avoid overwhelming it with health checking, but it is still recommended that health checks triggered as a result of a failed operation attempt to use the operation result code to decide whether it may be necessary to actually attempt to communicate with the server.

Further, it may also be useful to have more stringent criteria for promoting the health of a server than for demoting it in order to avoid a ping-pong effect that may occur if a server is hovering near the border between AVAILABLE and DEGRADED or between DEGRADED and UNAVAILABLE. For example, if a health check attempts to perform an operation in the backend server and the response time for that operation is taken into account when determining the server health, it might be better to require a lower response time in order to transition from DEGRADED to AVAILABLE than was originally required to transition from AVAILABLE to DEGRADED.

Configuring LDAP Health Checks

In order to configure an LDAP health check created using this API, use a command like:

      dsconfig create-ldap-health-check \
           --check-name "{check-name}" \
           --type third-party \
           --set enabled:true \
           --set "extension-class:{class-name}" \
           --set "extension-argument:{name=value}"
 

where "{check-name}" is the name to use for the LDAP health check instance, "{class-name}" is the fully-qualified name of the Java class that extends com.unboundid.directory.sdk.proxy.api.LDAPHealthCheck, and "{name=value}" represents name-value pairs for any arguments to provide to the LDAP health check. If multiple arguments should be provided to the LDAP health check, then the "--set extension-argument:{name=value}" option should be provided multiple times.

See Also:

ScriptedLDAPHealthCheck

Constructor Summary

Constructors

Constructor and Description
LDAPHealthCheck() Creates a new instance of this LDAP health check.

Method Summary

Modifier and Type	Method and Description
ResultCode	applyConfiguration(LDAPHealthCheckConfig config, ArgumentParser parser, java.util.List<java.lang.String> adminActionsRequired, java.util.List<java.lang.String> messages) Attempts to apply the configuration from the provided argument parser to this extension.
abstract HealthCheckResult	checkAvailableServer(BackendServer backendServer, LDAPConnection connection) Attempts to determine the health of the provided LDAP external server whose last health check result indicated that the server had a state of AVAILABLE.
abstract HealthCheckResult	checkDegradedServer(BackendServer backendServer, LDAPConnection connection) Attempts to determine the health of the provided LDAP external server whose last health check result indicated that the server had a state of DEGRADED.
abstract HealthCheckResult	checkFailedOperation(CompletedProxyOperationContext operationContext, LDAPException exception, BackendServer backendServer) Attempts to determine the health of the provided LDAP external server in which an attempted operation did not complete successfully.
abstract HealthCheckResult	checkUnavailableServer(BackendServer backendServer, LDAPConnection connection) Attempts to determine the health of the provided LDAP external server whose last health check result indicated that the server had a state of UNAVAILABLE.
void	defineConfigArguments(ArgumentParser parser) Updates the provided argument parser to define any configuration arguments which may be used by this extension.
void	finalizeLDAPHealthCheck() Performs any cleanup which may be necessary when this LDAP health check is to be taken out of service.
java.util.Map<java.util.List<java.lang.String>,java.lang.String>	getExamplesArgumentSets() Retrieves a map containing examples of configurations that may be used for this extension.
abstract java.lang.String[]	getExtensionDescription() Retrieves a human-readable description for this extension.
abstract java.lang.String	getExtensionName() Retrieves a human-readable name for this extension.
void	initializeLDAPHealthCheck(ProxyServerContext serverContext, LDAPHealthCheckConfig config, ArgumentParser parser) Initializes this LDAP health check.
boolean	isConfigurationAcceptable(LDAPHealthCheckConfig config, ArgumentParser parser, java.util.List<java.lang.String> unacceptableReasons) Indicates whether the configuration represented by the provided argument parser is acceptable for use by this extension.
java.lang.String	toString() Retrieves a string representation of this LDAP health check.
abstract void	toString(java.lang.StringBuilder buffer) Appends a string representation of this LDAP health check to the provided buffer.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

LDAPHealthCheck

public LDAPHealthCheck()

Creates a new instance of this LDAP health check. All LDAP health check implementations must include a default constructor, but any initialization should generally be done in the initializeLDAPHealthCheck method.

Method Detail

getExtensionName

public abstract java.lang.String getExtensionName()

Retrieves a human-readable name for this extension.

Specified by:

getExtensionName in interface UnboundIDExtension

Returns:

A human-readable name for this extension.

getExtensionDescription

public abstract java.lang.String[] getExtensionDescription()

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.

Specified by:

getExtensionDescription in interface UnboundIDExtension

Returns:

A human-readable description for this extension, or null or an empty array if no description should be available.

defineConfigArguments

public void defineConfigArguments(ArgumentParser parser)
                           throws ArgumentException

Updates the provided argument parser to define any configuration arguments which may be used by this extension. The argument parser may also be updated to define relationships between arguments (e.g., to specify required, exclusive, or dependent argument sets).

Specified by:

defineConfigArguments in interface Configurable

Parameters:

parser - The argument parser to be updated with the configuration arguments which may be used by this extension.

Throws:

ArgumentException - If a problem is encountered while updating the provided argument parser.

initializeLDAPHealthCheck

public void initializeLDAPHealthCheck(ProxyServerContext serverContext,
                                      LDAPHealthCheckConfig config,
                                      ArgumentParser parser)
                               throws LDAPException

Initializes this LDAP health check.

Parameters:

serverContext - A handle to the server context for the Directory Proxy server in which this extension is running.

config - The general configuration for this LDAP health check.

parser - The argument parser which has been initialized from the configuration for this LDAP health check.

Throws:

LDAPException - If a problem occurs while initializing this LDAP health check.

isConfigurationAcceptable

public boolean isConfigurationAcceptable(LDAPHealthCheckConfig config,
                                         ArgumentParser parser,
                                         java.util.List<java.lang.String> unacceptableReasons)

Indicates whether the configuration represented by the provided argument parser is acceptable for use by this extension. The parser will have been used to parse any configuration available for this extension, and any automatic validation will have been performed. This method may be used to perform any more complex validation which cannot be performed automatically by the argument parser.

Specified by:

isConfigurationAcceptable in interface Reconfigurable<LDAPHealthCheckConfig>

Parameters:

config - The general configuration for this extension.

parser - The argument parser that has been used to parse the proposed configuration for this extension.

unacceptableReasons - A list to which messages may be added to provide additional information about why the provided configuration is not acceptable.

Returns:

true if the configuration in the provided argument parser appears to be acceptable, or false if not.

applyConfiguration

public ResultCode applyConfiguration(LDAPHealthCheckConfig config,
                                     ArgumentParser parser,
                                     java.util.List<java.lang.String> adminActionsRequired,
                                     java.util.List<java.lang.String> messages)

Attempts to apply the configuration from the provided argument parser to this extension.

Specified by:

applyConfiguration in interface Reconfigurable<LDAPHealthCheckConfig>

Parameters:

config - The general configuration for this extension.

parser - The argument parser that has been used to parse the new configuration for this extension.

adminActionsRequired - A list to which messages may be added to provide additional information about any additional administrative actions that may be required to apply some of the configuration changes.

messages - A list to which messages may be added to provide additional information about the processing performed by this method.

Returns:

A result code providing information about the result of applying the configuration change. A result of SUCCESS should be used to indicate that all processing completed successfully. Any other result will indicate that a problem occurred during processing.

finalizeLDAPHealthCheck

public void finalizeLDAPHealthCheck()

Performs any cleanup which may be necessary when this LDAP health check is to be taken out of service.

checkAvailableServer

public abstract HealthCheckResult checkAvailableServer(BackendServer backendServer,
                                                       LDAPConnection connection)

Attempts to determine the health of the provided LDAP external server whose last health check result indicated that the server had a state of AVAILABLE. This method may be periodically invoked for AVAILABLE servers to determine whether their state has changed.

Parameters:

backendServer - A handle to the LDAP external server whose health is to be assessed.

connection - A connection that may be used to communicate with the server in the course of performing the evaluation. The health check should not do anything which may alter the state of this connection.

Returns:

Information about the result of the health check.

checkDegradedServer

public abstract HealthCheckResult checkDegradedServer(BackendServer backendServer,
                                                      LDAPConnection connection)

Attempts to determine the health of the provided LDAP external server whose last health check result indicated that the server had a state of DEGRADED. This method may be periodically invoked for DEGRADED servers to determine whether their state has changed.

Parameters:

backendServer - A handle to the LDAP external server whose health is to be assessed.

connection - A connection that may be used to communicate with the server in the course of performing the evaluation. The health check should not do anything which may alter the state of this connection.

Returns:

Information about the result of the health check.

checkUnavailableServer

public abstract HealthCheckResult checkUnavailableServer(BackendServer backendServer,
                                                         LDAPConnection connection)

Attempts to determine the health of the provided LDAP external server whose last health check result indicated that the server had a state of UNAVAILABLE. This method may be periodically invoked for UNAVAILABLE servers to determine whether their state has changed.

Parameters:

backendServer - A handle to the LDAP external server whose health is to be assessed.

connection - A connection that may be used to communicate with the server in the course of performing the evaluation. The health check should not do anything which may alter the state of this connection.

Returns:

Information about the result of the health check.

checkFailedOperation

public abstract HealthCheckResult checkFailedOperation(CompletedProxyOperationContext operationContext,
                                                       LDAPException exception,
                                                       BackendServer backendServer)

Attempts to determine the health of the provided LDAP external server in which an attempted operation did not complete successfully.

Parameters:

operationContext - A handle to the operation context for the operation that failed.

exception - The exception caught when attempting to process the associated operation in the backend server.

backendServer - A handle to the backend server in which the operation was processed.

Returns:

Information about the result of the health check.

toString

public final java.lang.String toString()

Retrieves a string representation of this LDAP health check.

Overrides:

toString in class java.lang.Object

Returns:

A string representation of this LDAP health check.

toString

public abstract void toString(java.lang.StringBuilder buffer)

Appends a string representation of this LDAP health check to the provided buffer.

Parameters:

buffer - The buffer to which the string representation should be appended.

getExamplesArgumentSets

public java.util.Map<java.util.List<java.lang.String>,java.lang.String> getExamplesArgumentSets()

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.

Specified by:

getExamplesArgumentSets in interface ExampleUsageProvider

Returns:

A map containing examples of configurations that may be used for this extension. It may be null or empty if there should not be any example argument sets.