org.apache.flume.serialization
Class DurablePositionTracker

java.lang.Object
  org.apache.flume.serialization.DurablePositionTracker

All Implemented Interfaces:

Closeable, PositionTracker

@InterfaceAudience.Private
@InterfaceStability.Evolving
public class DurablePositionTracker
extends Object
implements PositionTracker

Class that stores object state in an avro container file. The file is only ever appended to. At construction time, the object reads data from the end of the file and caches that data for use by a client application. After construction, reads never go to disk. Writes always flush to disk.

Note: This class is not thread-safe.

Method Summary

void	close()
static DurablePositionTracker	getInstance(File trackerFile, String target) If the file exists at startup, then read it, roll it, and open a new one.
long	getPosition()
String	getTarget()
void	storePosition(long position)

Methods inherited from class java.lang.Object

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

Method Detail

getInstance

public static DurablePositionTracker getInstance(File trackerFile,
                                                 String target)
                                          throws IOException

If the file exists at startup, then read it, roll it, and open a new one. We go through this to avoid issues with partial reads at the end of the file from a previous crash. If we append to a bad record, our writes may never be visible.

Parameters:

trackerFile -

target -

Returns:

Throws:

IOException

storePosition

public void storePosition(long position)
                   throws IOException

Specified by:

storePosition in interface PositionTracker

Throws:

IOException

getPosition

public long getPosition()

Specified by:

getPosition in interface PositionTracker

getTarget

public String getTarget()

Specified by:

getTarget in interface PositionTracker

close

public void close()
           throws IOException

Specified by:

close in interface Closeable

Specified by:

close in interface PositionTracker

Throws:

IOException