org.apache.accumulo.server.log

Class WalStateManager

java.lang.Object

org.apache.accumulo.server.log.WalStateManager

public class WalStateManager
extends Object

This class governs the space in Zookeeper that advertises the status of Write-Ahead Logs in use by tablet servers and the replication machinery.

The Master needs to know the state of the WALs to mark tablets during recovery. The GC needs to know when a log is no longer needed so it can be removed. The replication mechanism needs to know when a log is closed and can be forwarded to the destination table.

The state of the WALs is kept in Zookeeper under /accumulo/<instanceid>/wals. For each server, there is a znode formatted like the TServerInstance.toString(): "host:port[sessionid]". Under the server znode, is a node for each log, using the UUID for the log. In each of the WAL znodes, is the current state of the log, and the full path to the log.

The state [OPEN, CLOSED, UNREFERENCED] is what the tablet server believes to be the state of the file.

In the event of a recovery, the log is identified as belonging to a dead server. The master will update the tablets assigned to that server with log references. Once all tablets have been reassigned and the log references are removed, the log will be eligible for deletion.

Even when a log is UNREFERENCED by the tablet server, the replication mechanism may still need the log. The GC will defer log removal until replication is finished with it.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
class	WalStateManager.WalMarkerException
static class	WalStateManager.WalState

Field Summary

Fields

Modifier and Type	Field and Description
static String	ZWALS

Constructor Summary

Constructors

Constructor and Description
WalStateManager(Instance instance, ZooReaderWriter zoo)

Method Summary

Modifier and Type	Method and Description
void	addNewWalMarker(TServerInstance tsi, org.apache.hadoop.fs.Path path)
void	closeWal(TServerInstance instance, org.apache.hadoop.fs.Path path)
void	forget(TServerInstance instance)
Map<TServerInstance,List<UUID>>	getAllMarkers()
Map<org.apache.hadoop.fs.Path,WalStateManager.WalState>	getAllState()
List<org.apache.hadoop.fs.Path>	getWalsInUse(TServerInstance tsi)
void	initWalMarker(TServerInstance tsi)
void	removeWalMarker(TServerInstance instance, UUID uuid)
Pair<WalStateManager.WalState,org.apache.hadoop.fs.Path>	state(TServerInstance instance, UUID uuid)
void	walUnreferenced(TServerInstance tsi, org.apache.hadoop.fs.Path path)

Methods inherited from class java.lang.Object

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

Field Detail

ZWALS

public static final String ZWALS

See Also:

Constant Field Values

Constructor Detail

WalStateManager

public WalStateManager(Instance instance,
                       ZooReaderWriter zoo)

Method Detail

initWalMarker

public void initWalMarker(TServerInstance tsi)
                   throws WalStateManager.WalMarkerException

Throws:

WalStateManager.WalMarkerException

addNewWalMarker

public void addNewWalMarker(TServerInstance tsi,
                            org.apache.hadoop.fs.Path path)
                     throws WalStateManager.WalMarkerException

Throws:

WalStateManager.WalMarkerException

walUnreferenced

public void walUnreferenced(TServerInstance tsi,
                            org.apache.hadoop.fs.Path path)
                     throws WalStateManager.WalMarkerException

Throws:

WalStateManager.WalMarkerException

getWalsInUse

public List<org.apache.hadoop.fs.Path> getWalsInUse(TServerInstance tsi)
                                             throws WalStateManager.WalMarkerException

Throws:

WalStateManager.WalMarkerException

getAllMarkers

public Map<TServerInstance,List<UUID>> getAllMarkers()
                                              throws WalStateManager.WalMarkerException

Throws:

WalStateManager.WalMarkerException

state

public Pair<WalStateManager.WalState,org.apache.hadoop.fs.Path> state(TServerInstance instance,
                                                                      UUID uuid)
                                                               throws WalStateManager.WalMarkerException

Throws:

WalStateManager.WalMarkerException

getAllState

public Map<org.apache.hadoop.fs.Path,WalStateManager.WalState> getAllState()
                                                                    throws WalStateManager.WalMarkerException

Throws:

WalStateManager.WalMarkerException

removeWalMarker

public void removeWalMarker(TServerInstance instance,
                            UUID uuid)
                     throws WalStateManager.WalMarkerException

Throws:

WalStateManager.WalMarkerException

forget

public void forget(TServerInstance instance)
            throws WalStateManager.WalMarkerException

Throws:

WalStateManager.WalMarkerException

closeWal

public void closeWal(TServerInstance instance,
                     org.apache.hadoop.fs.Path path)
              throws WalStateManager.WalMarkerException

Throws:

WalStateManager.WalMarkerException