alluxio.master.journal

Class MergeJournalContext

java.lang.Object

alluxio.master.journal.MergeJournalContext

All Implemented Interfaces:

JournalContext, Closeable, AutoCloseable, java.util.function.Supplier<JournalContext>

@NotThreadSafe
public final class MergeJournalContext
extends Object
implements JournalContext

Context for merging journal entries together for a wrapped journal context. This is used so that we can combine several journal entries into one using a merge function. This prevents partial writes of these journal entries causing system to be left in an inconsistent state. For example, createFile without completing the file. This class will only merge the relevant inode entries for a particular URL. File operations to other URIs will be passed to the underlying JournalContext, and will not be buffered. Note that any buffered journal entries are not persisted and they will only be persisted when close is called on them. Closing the MergeJournalContext will also not close the enclosed journal context.

Field Summary

Fields

Modifier and Type	Field and Description
static int	MAX_ENTRIES

Constructor Summary

Constructors

Constructor and Description
MergeJournalContext(JournalContext journalContext, AlluxioURI uri, java.util.function.UnaryOperator<List<Journal.JournalEntry>> merger) Constructs a MergeJournalContext.

Method Summary

Modifier and Type	Method and Description
void	append(Journal.JournalEntry entry)
void	close()
void	flush() Flushes all the entries appended by the journal context so far.

Methods inherited from class java.lang.Object

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

Methods inherited from interface alluxio.master.journal.JournalContext

get

Field Detail

MAX_ENTRIES

public static final int MAX_ENTRIES

See Also:

Constant Field Values

Constructor Detail

MergeJournalContext

public MergeJournalContext(JournalContext journalContext,
                           AlluxioURI uri,
                           java.util.function.UnaryOperator<List<Journal.JournalEntry>> merger)

Constructs a MergeJournalContext.

Parameters:

journalContext - the journal context to wrap

uri - Alluxio URI that needs merging

merger - merging function which will merge multiple journal entries into one

Method Detail

append

public void append(Journal.JournalEntry entry)

Specified by:

append in interface JournalContext

Parameters:

entry - the Journal.JournalEntry to append to the journal

flush

public void flush()
           throws UnavailableException

Description copied from interface: JournalContext

Flushes all the entries appended by the journal context so far. This method can be called multiple times within the life cycle of the journal context The journals will be committed synchronously (example MasterJournalContext, or only added into the async journal writer (example MetadataSyncMergeJournalContext, based on different implementations.

Specified by:

flush in interface JournalContext

Throws:

UnavailableException

close

public void close()
           throws UnavailableException

Specified by:

close in interface JournalContext

Specified by:

close in interface Closeable

Specified by:

close in interface AutoCloseable

Throws:

UnavailableException