alluxio.master.journalv0

Interface JournalReader

All Known Implementing Classes:

UfsJournalReader

@NotThreadSafe
public interface JournalReader

This class manages reading from the journal. The reading must occur in two phases: 1. First, the checkpoint must be read. 2. Afterwards, logs are read in order they were created. Only completed logs are read, so the last log currently being written is not read until it is marked as complete.

Method Summary

Modifier and Type	Method and Description
JournalInputStream	getCheckpointInputStream() Gets the JournalInputStream for the journal checkpoint.
long	getCheckpointLastModifiedTimeMs()
JournalInputStream	getNextInputStream()
boolean	isValid() Checks to see if the journal checkpoint has not been updated.

Method Detail

isValid

boolean isValid()

Checks to see if the journal checkpoint has not been updated. If it has been updated since the creation of this reader, this reader is no longer valid.

Returns:

true if the checkpoint has not been updated

getCheckpointInputStream

JournalInputStream getCheckpointInputStream()
                                     throws IOException

Gets the JournalInputStream for the journal checkpoint. This must be called before calling getNextInputStream().

Returns:

the JournalInputStream for the journal checkpoint

Throws:

IOException

getNextInputStream

JournalInputStream getNextInputStream()
                               throws IOException

Returns:

the input stream for the next completed log. Will return null if the next completed log does not exist yet.

Throws:

IOException

getCheckpointLastModifiedTimeMs

long getCheckpointLastModifiedTimeMs()
                              throws IOException

Returns:

the last modified time of the checkpoint in ms

Throws:

IOException