org.apache.hadoop.hbase.coprocessor

Interface WALObserver

All Superinterfaces:

Coprocessor

All Known Implementing Classes:

BaseWALObserver

@InterfaceAudience.LimitedPrivate(value="Coprocesssor")
@InterfaceStability.Evolving
public interface WALObserver
extends Coprocessor

It's provided to have a way for coprocessors to observe, rewrite, or skip WALEdits as they are being written to the WAL. Note that implementers of WALObserver will not see WALEdits that report themselves as empty via WALEdit.isEmpty(). RegionObserver provides hooks for adding logic for WALEdits in the region context during reconstruction, Defines coprocessor hooks for interacting with operations on the WAL.

Nested Class Summary

Nested classes/interfaces inherited from interface org.apache.hadoop.hbase.Coprocessor

Coprocessor.State

Field Summary

Fields inherited from interface org.apache.hadoop.hbase.Coprocessor

PRIORITY_HIGHEST, PRIORITY_LOWEST, PRIORITY_SYSTEM, PRIORITY_USER, VERSION

Method Summary

Methods

Modifier and Type	Method and Description
void	postWALWrite(ObserverContext<? extends WALCoprocessorEnvironment> ctx, HRegionInfo info, WALKey logKey, WALEdit logEdit) Called after a WALEdit is writen to WAL.
void	postWALWrite(ObserverContext<WALCoprocessorEnvironment> ctx, HRegionInfo info, HLogKey logKey, WALEdit logEdit) Deprecated. use postWALWrite(ObserverContext, HRegionInfo, WALKey, WALEdit)
boolean	preWALWrite(ObserverContext<? extends WALCoprocessorEnvironment> ctx, HRegionInfo info, WALKey logKey, WALEdit logEdit) Called before a WALEdit is writen to WAL.
boolean	preWALWrite(ObserverContext<WALCoprocessorEnvironment> ctx, HRegionInfo info, HLogKey logKey, WALEdit logEdit) Deprecated. use preWALWrite(ObserverContext, HRegionInfo, WALKey, WALEdit)

Methods inherited from interface org.apache.hadoop.hbase.Coprocessor

start, stop

Method Detail

preWALWrite

boolean preWALWrite(ObserverContext<? extends WALCoprocessorEnvironment> ctx,
                  HRegionInfo info,
                  WALKey logKey,
                  WALEdit logEdit)
                    throws IOException

Called before a WALEdit is writen to WAL.

Returns:

true if default behavior should be bypassed, false otherwise

Throws:

IOException

preWALWrite

@Deprecated
boolean preWALWrite(ObserverContext<WALCoprocessorEnvironment> ctx,
                             HRegionInfo info,
                             HLogKey logKey,
                             WALEdit logEdit)
                    throws IOException

Deprecated. use preWALWrite(ObserverContext, HRegionInfo, WALKey, WALEdit)

Called before a WALEdit is writen to WAL. This method is left in place to maintain binary compatibility with older WALObservers. If an implementation directly overrides preWALWrite(ObserverContext, HRegionInfo, WALKey, WALEdit) then this version won't be called at all, barring problems with the Security Manager. To work correctly in the presence of a strict Security Manager, or in the case of an implementation that relies on a parent class to implement preWALWrite, you should implement this method as a call to the non-deprecated version. Users of this method will see all edits that can be treated as HLogKey. If there are edits that can't be treated as HLogKey they won't be offered to coprocessors that rely on this method. If a coprocessor gets skipped because of this mechanism, a log message at ERROR will be generated per coprocessor on the logger for CoprocessorHost once per classloader.

Returns:

true if default behavior should be bypassed, false otherwise

Throws:

IOException

postWALWrite

void postWALWrite(ObserverContext<? extends WALCoprocessorEnvironment> ctx,
                HRegionInfo info,
                WALKey logKey,
                WALEdit logEdit)
                  throws IOException

Called after a WALEdit is writen to WAL.

Throws:

IOException

postWALWrite

@Deprecated
void postWALWrite(ObserverContext<WALCoprocessorEnvironment> ctx,
                           HRegionInfo info,
                           HLogKey logKey,
                           WALEdit logEdit)
                  throws IOException

Deprecated. use postWALWrite(ObserverContext, HRegionInfo, WALKey, WALEdit)

Called after a WALEdit is writen to WAL. This method is left in place to maintain binary compatibility with older WALObservers. If an implementation directly overrides postWALWrite(ObserverContext, HRegionInfo, WALKey, WALEdit) then this version won't be called at all, barring problems with the Security Manager. To work correctly in the presence of a strict Security Manager, or in the case of an implementation that relies on a parent class to implement preWALWrite, you should implement this method as a call to the non-deprecated version. Users of this method will see all edits that can be treated as HLogKey. If there are edits that can't be treated as HLogKey they won't be offered to coprocessors that rely on this method. If a coprocessor gets skipped because of this mechanism, a log message at ERROR will be generated per coprocessor on the logger for CoprocessorHost once per classloader.

Throws:

IOException