UnboundID Server SDK

Ping Identity
UnboundID Server SDK Documentation

ExampleErrorLogger.java

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package com.unboundid.directory.sdk.examples;



import java.io.File;
import java.io.FileWriter;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Date;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.concurrent.atomic.AtomicLong;

import com.unboundid.directory.sdk.common.api.DiskSpaceConsumer;
import com.unboundid.directory.sdk.common.api.ErrorLogger;
import com.unboundid.directory.sdk.common.api.MonitorProvider;
import com.unboundid.directory.sdk.common.config.ErrorLoggerConfig;
import com.unboundid.directory.sdk.common.types.LogCategory;
import com.unboundid.directory.sdk.common.types.LogSeverity;
import com.unboundid.directory.sdk.common.types.RegisteredDiskSpaceConsumer;
import com.unboundid.directory.sdk.common.types.RegisteredMonitorProvider;
import com.unboundid.directory.sdk.common.types.ServerContext;
import com.unboundid.ldap.sdk.Attribute;
import com.unboundid.ldap.sdk.LDAPException;
import com.unboundid.ldap.sdk.ResultCode;
import com.unboundid.util.StaticUtils;
import com.unboundid.util.args.ArgumentException;
import com.unboundid.util.args.ArgumentParser;
import com.unboundid.util.args.FileArgument;



/**
 * This class provides a simple example of an error logger that will append a
 * message to a specified file about any errors, warnings, or events in the
 * server.  It takes a single configuration argument:
 * <UL>
 *   <LI>log-file -- The path to the log file that will be written.  This must
 *       be provided.</LI>
 * </UL>
 * This example also demonstrates how to register an ad-hoc monitor provider
 * with the server, without having to add any server-side configuration.
 */
public final class ExampleErrorLogger
       extends ErrorLogger
       implements DiskSpaceConsumer
{
  /**
   * The name of the argument that will be used for the argument used to specify
   * the path to the log file.
   */
  private static final String ARG_NAME_LOG_FILE = "log-file";



  // The general configuration for this error logger.
  private volatile ErrorLoggerConfig config;

  // The path to the log file to be written.
  private volatile File logFile;

  // The lock that will be used to synchronize logging activity.
  private final Object loggerLock;

  // The print writer that will be used to actually write the log messages.
  private volatile PrintWriter writer;

  // A counter used to keep track of how many messages have been logged.
  private AtomicLong messageCount;

  // The registered disk space consumer for this error logger.
  private volatile RegisteredDiskSpaceConsumer registeredConsumer;

  //The registered monitor provider for this error logger.
  private RegisteredMonitorProvider monitorProvider;

  // The server context for the server in which this extension is running.
  private ServerContext serverContext;



  /**
   * Creates a new instance of this error logger.  All error logger
   * implementations must include a default constructor, but any initialization
   * should generally be done in the {@code initializeErrorLogger} method.
   */
  public ExampleErrorLogger()
  {
    loggerLock = new Object();
  }



  /**
   * Retrieves a human-readable name for this extension.
   *
   * @return  A human-readable name for this extension.
   */
  @Override()
  public String getExtensionName()
  {
    return "Example Error Logger";
  }



  /**
   * 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 error logger serves an example that may be used to demonstrate " +
           "the process for creating a third-party error logger.  It will " +
           "write a line to a specified file for each error log message " +
           "generated by the server.",

      "For simplicity, this example logger does not take care of all tasks " +
           "that would be necessary for production use.  For example, it " +
           "does not include any rotation or retention functionality, so the " +
           "file will grow without bounds.  Further, while it is threadsafe, " +
           "it does so using simple Java synchronized blocks which is a " +
           "simple way to achieve the necessary safety, but does not " +
           "necessarily allow for the highest performance or concurrency.",

      "Because this error logger writes to disk, it also serves as an " +
           "example of a disk space consumer so that the server may track " +
           "available space on the disk containing the log file and " +
           "potentially warn administrators if usable space becomes too low."
    };
  }



  /**
   * Updates the provided argument parser to define any configuration arguments
   * which may be used by this error logger.  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 error logger.
   *
   * @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 path to the log file.
    Character shortIdentifier = null;
    String    longIdentifier  = ARG_NAME_LOG_FILE;
    boolean   required        = true;
    int       maxOccurrences  = 1;
    String    placeholder     = "{path}";
    String    description     = "The path to the log file to be written.  " +
         "Non-absolute paths will be treated as relative to the server root.";
    boolean   fileMustExist   = false;
    boolean   parentMustExist = true;
    boolean   mustBeFile      = true;
    boolean   mustBeDirectory = false;

    parser.addArgument(new FileArgument(shortIdentifier, longIdentifier,
         required, maxOccurrences, placeholder, description, fileMustExist,
         parentMustExist, mustBeFile, mustBeDirectory));
  }



  /**
   * Initializes this error logger.
   *
   * @param  serverContext  A handle to the server context for the server in
   *                        which this extension is running.
   * @param  config         The general configuration for this error logger.
   * @param  parser         The argument parser which has been initialized from
   *                        the configuration for this error logger.
   *
   * @throws  LDAPException  If a problem occurs while initializing this error
   *                         logger.
   */
  @Override()
  public void initializeErrorLogger(final ServerContext serverContext,
                                    final ErrorLoggerConfig config,
                                    final ArgumentParser parser)
         throws LDAPException
  {
    this.serverContext = serverContext;
    this.config        = config;
    this.messageCount  = new AtomicLong();

    // Create the logger and open the log file.
    try
    {
      final FileArgument arg =
           (FileArgument) parser.getNamedArgument(ARG_NAME_LOG_FILE);
      logFile = arg.getValue();
      writer  = new PrintWriter(new FileWriter(logFile, true));
    }
    catch (final Exception e)
    {
      serverContext.debugCaught(e);
      throw new LDAPException(ResultCode.OTHER,
           "Unable to open file " + logFile.getAbsolutePath() +
                " for writing:  " + StaticUtils.getExceptionMessage(e),
           e);
    }

    // Register as a disk space consumer since we will be writing to the log
    // file.
    registeredConsumer = serverContext.registerDiskSpaceConsumer(this);

    // Register a custom monitor provider to expose the number of messages
    // logged and the size of the log file.
    monitorProvider = serverContext.registerMonitorProvider(
                            new SimpleMonitorProvider(), config);
  }



  /**
   * Indicates whether the configuration contained in the provided argument
   * parser represents a valid configuration for this extension.
   *
   * @param  config               The general configuration for this error
   *                              logger.
   * @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 ErrorLoggerConfig config,
                      final ArgumentParser parser,
                      final List<String> unacceptableReasons)
  {
    // The argument parser will handle all of the necessary validation, so
    // we don't need to do anything here.
    return true;
  }



  /**
   * Attempts to apply the configuration contained in the provided argument
   * parser.
   *
   * @param  config                The general configuration for this error
   *                               logger.
   * @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 ErrorLoggerConfig config,
                                       final ArgumentParser parser,
                                       final List<String> adminActionsRequired,
                                       final List<String> messages)
  {
    this.config = config;

    // Get the path to the log file from the new config.
    final FileArgument arg =
         (FileArgument) parser.getNamedArgument(ARG_NAME_LOG_FILE);
    final File newFile = arg.getValue();

    // If the log file path hasn't changed, then we don't need to do anything.
    if (newFile.equals(logFile))
    {
      return ResultCode.SUCCESS;
    }

    // Create a print writer that can be used to write to the new log file.
    final PrintWriter newWriter;
    try
    {
      newWriter = new PrintWriter(new FileWriter(newFile, true));
    }
    catch (final Exception e)
    {
      serverContext.debugCaught(e);
      messages.add("Unable to open new log file " + newFile.getAbsolutePath() +
           " for writing:  " + StaticUtils.getExceptionMessage(e));
      return ResultCode.OTHER;
    }

    // Swap the new logger into place.
    final PrintWriter oldWriter;
    synchronized (loggerLock)
    {
      oldWriter = writer;
      writer = newWriter;
      logFile = newFile;
    }

    // Close the old logger.
    oldWriter.close();

    // Re-register the monitor provider with the new config.
    serverContext.deregisterMonitorProvider(monitorProvider);
    monitorProvider = serverContext.registerMonitorProvider(
                                    new SimpleMonitorProvider(), config);

    return ResultCode.SUCCESS;
  }



  /**
   * Performs any cleanup which may be necessary when this error logger is
   * to be taken out of service.
   */
  @Override()
  public void finalizeErrorLogger()
  {
    synchronized (loggerLock)
    {
      if (registeredConsumer != null)
      {
        serverContext.deregisterDiskSpaceConsumer(registeredConsumer);
      }

      writer.close();
      writer = null;
      logFile = null;
    }

    serverContext.deregisterMonitorProvider(monitorProvider);
  }



  /**
   * Records information about the provided message, if appropriate.
   *
   * @param  category   The category for the message to be logged.
   * @param  severity   The severity for the message to be logged.
   * @param  messageID  The unique identifier with which the message text is
   *                    associated.
   * @param  message    The message to be logged.
   */
  @Override()
  public void logError(final LogCategory category, final LogSeverity severity,
                       final long messageID, final String message)
  {
    final StringBuilder buffer = new StringBuilder();
    buffer.append(new Date());
    buffer.append(" severity=");
    buffer.append(severity.name());
    buffer.append(" message=\"");
    buffer.append(message);
    buffer.append('"');

    synchronized (loggerLock)
    {
      if (writer == null)
      {
        // This should only happen if the logger has been shut down.
        return;
      }

      writer.println(buffer.toString());
    }

    // Increment the message counter.
    messageCount.incrementAndGet();
  }



  /**
   * 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_LOG_FILE + "=logs/example-error.log"),
         "Write error log messages to the logs/example-error.log file below " +
              "the server root.");

    return exampleMap;
  }



  /**
   * Retrieves the name that should be used to identify this disk space
   * consumer.
   *
   * @return  The name that should be used to identify this disk space consumer.
   */
  public String getDiskSpaceConsumerName()
  {
    return "Example Error Logger " + config.getConfigObjectName();
  }



  /**
   * Retrieves a list of filesystem paths in which this disk space consumer may
   * store files which may consume a significant amount of space.  It is
   * generally recommended that the paths be directories, but they may also be
   * individual files.
   *
   * @return  A list of filesystem paths in which this disk space consumer may
   *          store files which may consume a significant amount of space.
   */
  public List<File> getDiskSpaceConsumerPaths()
  {
    return Arrays.asList(logFile);
  }



  /**
   * A simple implementation of MonitorProvider that we can register with the
   * server through the ServerContext object. This exposes the number of
   * messages that have been logged and the current size of the log file.
   */
  private class SimpleMonitorProvider extends MonitorProvider
  {
    /**
     * Retrieves a human-readable name for this extension. This is not used
     * since we are registering this MonitorProvider through the ServerContext
     * object (e.g. it is not a stand-alone extension).
     *
     * @return  A human-readable name for this extension.
     */
    @Override
    public String getExtensionName()
    {
      return "SimpleMonitorProvider";
    }



    /**
     * 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. This is not used since we are registering this
     * MonitorProvider through the ServerContext object (e.g. it is not a
     * stand-alone extension).
     *
     * @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 null;
    }



    /**
     * Retrieves the name that identifies this monitor provider instance.  It
     * will be used as the value of the naming attribute for monitor entries.
     * Each monitor provider instance must have a unique name.
     *
     * @return  The name that identifies this monitor provider instance.
     */
    @Override
    public String getMonitorInstanceName()
    {
      return "ExampleErrorLogger Monitor";
    }



    /**
     * Retrieves the name of the object class that will be used for monitor
     * entries created from this monitor provider.  This does not need to be
     * defined in the server schema.  It may be {@code null} if a default object
     * class should be used.
     *
     * @return  The name of the object class that will be used for monitor
     *          entries created from this monitor provider.
     */
    @Override
    public String getMonitorObjectClass()
    {
      return "error-logger-monitor-entry";
    }



    /**
     * Retrieves a list of attributes containing the data to include in the
     * monitor entry generated from this monitor provider.
     *
     * @return  A list of attributes containing the data to include in the
     *          monitor entry generated from this monitor provider.
     */
    @Override
    public List<Attribute> getMonitorAttributes()
    {
      List<Attribute> attributes = new ArrayList<Attribute>(2);
      attributes.add(new Attribute("num-messages-logged",
                                       String.valueOf(messageCount.get())));
      attributes.add(new Attribute("log-file-size",
                                       logFile.getTotalSpace() + " bytes"));
      return attributes;
    }
  }
}