org.apache.hadoop.hbase.util

Class RotateFile

java.lang.Object

org.apache.hadoop.hbase.util.RotateFile

@InterfaceAudience.Private
public class RotateFile
extends Object

A file storage which supports atomic update through two files, i.e, rotating. The implementation does not require atomic rename.

Constructor Summary

Constructors

Constructor and Description
RotateFile(org.apache.hadoop.fs.FileSystem fs, org.apache.hadoop.fs.Path dir, String name, long maxFileSize) Constructs a new RotateFile object with the given parameters.

Method Summary

Modifier and Type	Method and Description
void	delete() Deletes the two files used for rotating data.
byte[]	read() Reads the content of the rotate file by selecting the winner file based on the timestamp of the data inside the files.
void	write(byte[] data) Writes the given data to the next file in the rotation, with a timestamp calculated based on the previous timestamp and the current time to make sure it is greater than the previous timestamp.

Methods inherited from class java.lang.Object

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

Constructor Detail

RotateFile

public RotateFile(org.apache.hadoop.fs.FileSystem fs,
                  org.apache.hadoop.fs.Path dir,
                  String name,
                  long maxFileSize)

Constructs a new RotateFile object with the given parameters.

Parameters:

fs - the file system to use.

dir - the directory where the files will be created.

name - the base name for the files.

maxFileSize - the maximum size of each file.

Method Detail

read

public byte[] read()
            throws IOException

Reads the content of the rotate file by selecting the winner file based on the timestamp of the data inside the files. It reads the content of both files and selects the one with the latest timestamp as the winner. If a file is incomplete or does not exist, it logs the error and moves on to the next file. It returns the content of the winner file as a byte array. If none of the files have valid data, it returns null.

Returns:

a byte array containing the data from the winner file, or null if no valid data is found.

Throws:

IOException - if an error occurs while reading the files.

write

public void write(byte[] data)
           throws IOException

Writes the given data to the next file in the rotation, with a timestamp calculated based on the previous timestamp and the current time to make sure it is greater than the previous timestamp. The method also deletes the previous file, which is no longer needed.

Notice that, for a newly created RotateFile instance, you need to call read() first to initialize the nextFile index, before calling this method.

Parameters:

data - the data to be written to the file

Throws:

IOException - if an I/O error occurs while writing the data to the file

delete

public void delete()
            throws IOException

Deletes the two files used for rotating data. If any of the files cannot be deleted, an IOException is thrown.

Throws:

IOException - if there is an error deleting either file