com.sleepycat.je.util

Class LogVerificationReadableByteChannel

java.lang.Object

com.sleepycat.je.util.LogVerificationReadableByteChannel

All Implemented Interfaces:

java.io.Closeable, java.lang.AutoCloseable, java.nio.channels.Channel, java.nio.channels.ReadableByteChannel

public class LogVerificationReadableByteChannel
extends java.lang.Object
implements java.nio.channels.ReadableByteChannel

Verifies the checksums in a ReadableByteChannel for a log file in a JE Environment. This class is similar to the LogVerificationInputStream class, but permits using NIO channels and direct buffers to provide better copying performance.

This ReadableByteChannel reads input from some other given ReadableByteChannel, and verifies checksums while reading. Its primary intended use is to verify log files that are being copied as part of a programmatic backup. It is critical that invalid files are not added to a backup set, since then both the live environment and the backup will be invalid.

The following example verifies log files as they are being copied. The DbBackup class should normally be used to obtain the array of files to be copied.

  void copyFilesNIO(final Environment env,
                    final String[] fileNames,
                    final File destDir,
                    final int bufSize)
      throws IOException, DatabaseException {

      final File srcDir = env.getHome();

      for (final String fileName : fileNames) {

          final File destFile = new File(destDir, fileName);
          final FileOutputStream fos = new FileOutputStream(destFile);
          final FileChannel foc = fos.getChannel();

          final File srcFile = new File(srcDir, fileName);
          final FileInputStream fis = new FileInputStream(srcFile);
          final FileChannel fic = fis.getChannel();
          final LogVerificationReadableByteChannel vic =
              new LogVerificationReadableByteChannel(env, fic, fileName);

          final ByteBuffer buf = ByteBuffer.allocateDirect(bufSize);

          try {
              while (true) {
                  final int len = vic.read(buf);
                  if (len < 0) {
                      break;
                  }
                  buf.flip();
                  foc.write(buf);
                  buf.clear();
              }
          } finally {
              fos.close();
              vic.close();
          }
      }
  }
 

It is important to read the entire underlying input stream until the end-of-file is reached to detect incomplete entries at the end of the log file.

See Also:

DbBackup, DbVerifyLog, LogVerificationInputStream

Constructor Summary

Constructors

Constructor and Description
LogVerificationReadableByteChannel(Environment env, java.nio.channels.ReadableByteChannel channel, java.lang.String fileName) Creates a verification input stream.

Method Summary

Modifier and Type	Method and Description
void	close()
boolean	isOpen()
int	read(java.nio.ByteBuffer buffer)

Methods inherited from class java.lang.Object

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

Constructor Detail

LogVerificationReadableByteChannel

public LogVerificationReadableByteChannel(Environment env,
                                          java.nio.channels.ReadableByteChannel channel,
                                          java.lang.String fileName)

Creates a verification input stream.

Parameters:

env - the Environment associated with the log

channel - the underlying ReadableByteChannel for the log to be read

fileName - the file name of the input stream, for reporting in the LogVerificationException. This should be a simple file name of the form NNNNNNNN.jdb, where NNNNNNNN is the file number in hexadecimal format.

Throws:

EnvironmentFailureException - if an unexpected, internal or environment-wide failure occurs

Method Detail

read

public int read(java.nio.ByteBuffer buffer)
         throws java.io.IOException

This method reads the underlying ReadableByteChannel and verifies the contents of the stream.

Specified by:

read in interface java.nio.channels.ReadableByteChannel

Throws:

LogVerificationException - if a checksum cannot be verified or a log entry is determined to be invalid by examining its contents

EnvironmentFailureException - if an unexpected, internal or environment-wide failure occurs

java.io.IOException

close

public void close()
           throws java.io.IOException

This method calls close on the underlying channel.

Specified by:

close in interface java.io.Closeable

Specified by:

close in interface java.lang.AutoCloseable

Specified by:

close in interface java.nio.channels.Channel

Throws:

java.io.IOException

isOpen

public boolean isOpen()

This method calls isOpen on the underlying channel.

Specified by:

isOpen in interface java.nio.channels.Channel