com.bigdata.journal

Class CommitCounterUtility

java.lang.Object

com.bigdata.journal.CommitCounterUtility

public class CommitCounterUtility
extends Object

Utility class for operations on files that are named using a commit counter.

The commit counter based files are arranged in a heirarchial directory structure with 3 digits per directory and 7 directory levels. These levels are labeled with depths [0..6]. The root directory is at depth ZERO (0). Each directory contains up to 1000 children. The children in the non-leaf directories are subdirectories labeled 0..999. The leaf directories are at depth SIX (6). Leaf directories contain files. Each file in a leaf directory is labeled with a 21 digit base name and some purpose specific file extension. Each such file has data for the specific commit point encoded by the basename of the file.

Author:

Bryan Thompson

Constructor Summary

Constructors

Constructor and Description
CommitCounterUtility()

Method Summary

Methods

Modifier and Type	Method and Description
static File	findGreatestCommitCounter(File f, FileFilter fileFilter) Find and return the File associated with the greatest commit counter.
static String	getBaseName(String name, String ext) Return the basename of the file (strip off the extension).
static int	getBasenameDigits() The #of digits (21) in the base file name for a commit counter as formatted by getCommitCounterStr(long).
static File	getCommitCounterFile(File dir, long commitCounter, String ext) Return the name of the File associated with the commitCounter.
static String	getCommitCounterStr(long commitCounter) Format the commit counter with leading zeros such that it will be lexically ordered in the file system.
static int	getDigitsPerDirectory() The number of base-10 digits per directory level ( ).
static int	getFilesPerDirectory() The number of files per directory ().
static int	getLeafDirectoryDepth() The depth of a leaf directory ().
static int	getRootDirectoryDepth() The depth of the root directory ().
static long	parseCommitCounterFile(String name, String ext) Parse out the commitCounter from the file name.
static void	recursiveDelete(boolean errorIfDeleteFails, File f, FileFilter fileFilter) Recursively removes any files and subdirectories and then removes the file (or directory) itself.

Methods inherited from class java.lang.Object

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

Constructor Detail

CommitCounterUtility

public CommitCounterUtility()

Method Detail

getBasenameDigits

public static int getBasenameDigits()

The #of digits (21) in the base file name for a commit counter as formatted by getCommitCounterStr(long).

Note: 21 := (leafDirDepth+1) * digitsPerDir

getDigitsPerDirectory

public static int getDigitsPerDirectory()

The number of base-10 digits per directory level ( ). This allows children having labels 000...999. Thus there are 1000 children per directory.

getFilesPerDirectory

public static int getFilesPerDirectory()

The number of files per directory ().

getRootDirectoryDepth

public static int getRootDirectoryDepth()

The depth of the root directory ().

getLeafDirectoryDepth

public static int getLeafDirectoryDepth()

The depth of a leaf directory ().

getCommitCounterFile

public static File getCommitCounterFile(File dir,
                        long commitCounter,
                        String ext)

Return the name of the File associated with the commitCounter.

Parameters:

dir - The directory spanning all such files.

commitCounter - The commit counter for the current root block on the journal.

ext - The filename extension.

Returns:

The name of the corresponding snapshot file.

getCommitCounterStr

public static String getCommitCounterStr(long commitCounter)

Format the commit counter with leading zeros such that it will be lexically ordered in the file system.

Parameters:

commitCounter - The commit counter.

Returns:

The basename of the file consisting of the foramtted commit counter with the appropriate leading zeros.

parseCommitCounterFile

public static long parseCommitCounterFile(String name,
                          String ext)
                                   throws NumberFormatException

Parse out the commitCounter from the file name.

Parameters:

name - The file name

ext - The expected file extension.

Returns:

The commit counter from the file name.

Throws:

IllegalArgumentException - if either argument is null

NumberFormatException - if the file name can not be interpreted as a commit counter.

getBaseName

public static String getBaseName(String name,
                 String ext)

Return the basename of the file (strip off the extension).

Parameters:

name - The file name.

ext - The extension.

Returns:

The base name of the file without the extension.

recursiveDelete

public static void recursiveDelete(boolean errorIfDeleteFails,
                   File f,
                   FileFilter fileFilter)
                            throws IOException

Recursively removes any files and subdirectories and then removes the file (or directory) itself. Only files recognized by #getFileFilter() will be deleted.

Note: A dedicated version of this method exists here to thrown an IOException if we can not delete a file. This is deliberate. It is thrown to prevent a REBUILD from proceeding unless we can clear out the old snapshot and HALog files.

Parameters:

errorIfDeleteFails - When true and IOException is thrown if a file matching the filter or an empty directory matching the filter can not be removed. When false, that event is logged @ WARN instead.

f - A file or directory.

fileFilter - A filter matching the files and directories to be visited and removed. If directories are matched, then they will be removed iff they are empty. A depth first visitation is used, so the files and sub-directories will be cleared before we attempt to remove the parent directory.

Throws:

IOException - if any file or non-empty directory can not be deleted (iff errorIfDeleteFails is true).

findGreatestCommitCounter

public static File findGreatestCommitCounter(File f,
                             FileFilter fileFilter)
                                      throws IOException

Find and return the File associated with the greatest commit counter. This uses a reverse order search to locate the most recent file very efficiently.

Parameters:

f - The root of the directory structure for the snapshot or HALog files.

fileFilter - Either the SnapshotManager#SNAPSHOT_FILTER or the IHALogReader.HALOG_FILTER.

Returns:

The file from the directory structure associated with the greatest commit counter.

Throws:

IOException