alluxio.master.journal.ufs

Class UfsJournalReader

java.lang.Object

alluxio.master.journal.ufs.UfsJournalReader

All Implemented Interfaces:

JournalReader, Closeable, AutoCloseable

@NotThreadSafe
public final class UfsJournalReader
extends Object
implements JournalReader

Implementation of JournalReader that reads journal entries from a UFS. It can optionally read after a given sequence number. By default, it starts from 0 sequence number. If this reader runs in a primary master, it reads the incomplete log. If this reader runs in a secondary master, it does not read the incomplete log.

Constructor Summary

Constructors

Constructor and Description
UfsJournalReader(UfsJournal journal, long startSequenceId, boolean readIncompleteLog) Creates a new instance of UfsJournalReader.

Method Summary

Modifier and Type	Method and Description
void	close()
long	getNextSequenceNumber() Gets the the sequence number of the next journal log entry to read.
Journal.JournalEntry	read() Reads an entry from the journal.

Methods inherited from class java.lang.Object

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

Constructor Detail

UfsJournalReader

public UfsJournalReader(UfsJournal journal,
                        long startSequenceId,
                        boolean readIncompleteLog)

Creates a new instance of UfsJournalReader.

Parameters:

journal - the handle to the journal

startSequenceId - the sequence ID to start reading from

readIncompleteLog - whether to read incomplete logs

Method Detail

close

public void close()
           throws IOException

Specified by:

close in interface Closeable

Specified by:

close in interface AutoCloseable

Throws:

IOException

getNextSequenceNumber

public long getNextSequenceNumber()

Description copied from interface: JournalReader

Gets the the sequence number of the next journal log entry to read. This method is valid no matter whether this JournalReader is closed or not.

Specified by:

getNextSequenceNumber in interface JournalReader

Returns:

the next sequence number

read

public Journal.JournalEntry read()
                          throws IOException,
                                 InvalidJournalEntryException

Description copied from interface: JournalReader

Reads an entry from the journal. Return null if there is no more entry left.

Specified by:

read in interface JournalReader

Returns:

the journal entry, null if no more entry left

Throws:

InvalidJournalEntryException - if the journal entry is invalid (e.g. corrupted entry)

IOException