alluxio.master.journal

Interface JournalReader

All Superinterfaces:

AutoCloseable, Closeable

All Known Implementing Classes:

UfsJournalReader

@NotThreadSafe
public interface JournalReader
extends Closeable

This class manages reading from the journal.

Nested Class Summary

Nested Classes

Modifier and Type	Interface and Description
static class	JournalReader.State States that the reader can be after calling advance().

Method Summary

Modifier and Type	Method and Description
JournalReader.State	advance() Advances the reader to the next element.
CheckpointInputStream	getCheckpoint() Returns the input stream for reading a checkpoint.
Journal.JournalEntry	getEntry() Returns the next entry in the journal.
long	getNextSequenceNumber() Gets the the sequence number of the next journal log entry to read.

Methods inherited from interface java.io.Closeable

close

Method Detail

getEntry

Journal.JournalEntry getEntry()

Returns the next entry in the journal. This will be null unless the last call to advance() returned JournalReader.State.LOG. Multiple calls to getEntry without calling advance will return the same entry.

Returns:

the journal entry, or null if the next element isn't a journal entry

getCheckpoint

CheckpointInputStream getCheckpoint()

Returns the input stream for reading a checkpoint. This will be null unless the last call to advance() returned JournalReader.State.CHECKPOINT. Multiple calls to getCheckpoint without calling advance will return the same stream.

Returns:

the input stream for reading the checkpoint, or null if the next element isn't a checkpoint

getNextSequenceNumber

long getNextSequenceNumber()

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.

Returns:

the next sequence number

advance

JournalReader.State advance()
                     throws IOException

Advances the reader to the next element.

Returns:

the next element, see JournalReader.State

Throws:

IOException