alluxio.master.journal.ufs

Class UfsJournal

java.lang.Object

alluxio.master.journal.ufs.UfsJournal

All Implemented Interfaces:

Journal, Closeable, AutoCloseable

@ThreadSafe
public class UfsJournal
extends Object
implements Journal

Implementation of UFS-based journal. The journal is made up of 2 components: - The checkpoint: a snapshot of the master state - The log entries: incremental entries to apply to the checkpoint. The journal log entries must be self-contained. Checkpoint is considered as a compaction of a set of journal log entries. If the master does not do any checkpoint, the journal should still be sufficient. Journal file structure: journal_folder/version/logs/StartSequenceNumber-EndSequenceNumber journal_folder/version/checkpoints/0-EndSequenceNumber journal_folder/version/.tmp/random_id

Field Summary

Fields

Modifier and Type	Field and Description
static long	UNKNOWN_SEQUENCE_NUMBER This is set to Long.MAX_VALUE such that the current log can be sorted after any other completed logs.
static String	VERSION The journal version.

Constructor Summary

Constructors

Constructor and Description
UfsJournal(URI location, Master master, long quietPeriodMs, java.util.function.Supplier<Set<JournalSink>> journalSinks) Creates a new instance of UfsJournal.

Method Summary

Modifier and Type	Method and Description
void	checkpoint() Creates a checkpoint in this ufs journal.
void	close()
JournalContext	createJournalContext()
void	flush() Flushes the journal.
void	format() Formats the journal.
void	gainPrimacy() Transitions the journal from secondary to primary mode.
alluxio.master.journal.ufs.UfsJournalCheckpointWriter	getCheckpointWriter(long checkpointSequenceNumber)
protected static UnderFileSystemConfiguration	getJournalUfsConf()
URI	getLocation()
URI	getLogDir()
long	getNextSequenceNumberToCheckpoint()
long	getNextSequenceNumberToWrite()
long	getQuietPeriodMs()
UfsJournalReader	getReader(boolean readIncompleteLogs)
boolean	isFormatted()
void	losePrimacy() Transitions the journal from primary to secondary mode.
void	start() Starts the journal in secondary mode.
String	toString()

Methods inherited from class java.lang.Object

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

Field Detail

UNKNOWN_SEQUENCE_NUMBER

public static final long UNKNOWN_SEQUENCE_NUMBER

This is set to Long.MAX_VALUE such that the current log can be sorted after any other completed logs.

See Also:

Constant Field Values

VERSION

public static final String VERSION

The journal version.

See Also:

Constant Field Values

Constructor Detail

UfsJournal

public UfsJournal(URI location,
                  Master master,
                  long quietPeriodMs,
                  java.util.function.Supplier<Set<JournalSink>> journalSinks)

Creates a new instance of UfsJournal.

Parameters:

location - the location for this journal

master - the master to manage

quietPeriodMs - the amount of time to wait to pass without seeing a new journal entry when gaining primacy

journalSinks - a supplier for journal sinks

Method Detail

getJournalUfsConf

protected static UnderFileSystemConfiguration getJournalUfsConf()

Returns:

the ufs configuration to use for the journal operations

getLocation

public URI getLocation()

Specified by:

getLocation in interface Journal

Returns:

the journal location

flush

public void flush()
           throws IOException,
                  JournalClosedException

Flushes the journal.

Throws:

IOException

JournalClosedException

createJournalContext

public JournalContext createJournalContext()
                                    throws UnavailableException

Specified by:

createJournalContext in interface Journal

Returns:

a journal context for appending journal entries

Throws:

UnavailableException - if a context cannot be created because the journal has been closed.

start

public void start()
           throws IOException

Starts the journal in secondary mode.

Throws:

IOException

gainPrimacy

public void gainPrimacy()
                 throws IOException

Transitions the journal from secondary to primary mode. The journal will apply the latest journal entries to the state machine, then begin to allow writes.

Throws:

IOException

losePrimacy

public void losePrimacy()
                 throws IOException

Transitions the journal from primary to secondary mode. The journal will no longer allow writes, and the state machine is rebuilt from the journal and kept up to date.

Throws:

IOException

getQuietPeriodMs

public long getQuietPeriodMs()

Returns:

the quiet period for this journal

getReader

public UfsJournalReader getReader(boolean readIncompleteLogs)

Parameters:

readIncompleteLogs - whether the reader should read the latest incomplete log

Returns:

a reader for reading from the start of the journal

getCheckpointWriter

public alluxio.master.journal.ufs.UfsJournalCheckpointWriter getCheckpointWriter(long checkpointSequenceNumber)
                                                                          throws IOException

Parameters:

checkpointSequenceNumber - the next sequence number after the checkpoint

Returns:

a writer for writing a checkpoint

Throws:

IOException

getNextSequenceNumberToWrite

public long getNextSequenceNumberToWrite()

Returns:

the next sequence number to write

getNextSequenceNumberToCheckpoint

public long getNextSequenceNumberToCheckpoint()
                                       throws IOException

Returns:

the first log sequence number that hasn't yet been checkpointed

Throws:

IOException

isFormatted

public boolean isFormatted()
                    throws IOException

Returns:

whether the journal has been formatted

Throws:

IOException

format

public void format()
            throws IOException

Formats the journal.

Throws:

IOException

checkpoint

public void checkpoint()
                throws IOException

Creates a checkpoint in this ufs journal.

Throws:

IOException

getLogDir

public URI getLogDir()

Returns:

the log directory location

toString

public String toString()

Overrides:

toString in class Object

close

public void close()
           throws IOException

Specified by:

close in interface Closeable

Specified by:

close in interface AutoCloseable

Throws:

IOException