Package org.apache.fluo.api.observer

Interface Observer

All Known Subinterfaces:

StringObserver

All Known Implementing Classes:

AbstractObserver

Functional Interface:

This is a functional interface and can therefore be used as the assignment target for a lambda expression or method reference.

@FunctionalInterface
public interface Observer

Implemented by users to a watch a Column and be notified of changes to the Column via the process(TransactionBase, Bytes, Column) method.

In Fluo version 1.1.0 this was converted to a functional interface. This change along with the introduction of ObserverProvider allows Observers to be written as lambdas.

Since:

1.0.0

Nested Class Summary

Nested Classes

Modifier and Type	Interface	Description
static interface	Observer.Context	Deprecated. since 1.1.0.
static class	Observer.NotificationType
static class	Observer.ObservedColumn	Deprecated. since 1.1.0.

Method Summary

Modifier and Type	Method	Description
default void	close()	Deprecated. since 1.1.0.
default Observer.ObservedColumn	getObservedColumn()	Deprecated. since 1.1.0 Fluo will no longer call this method when observers are configured by FluoConfiguration.setObserverProvider(String).
default void	init(Observer.Context context)	Deprecated. since 1.1.0.
void	process(TransactionBase tx, Bytes row, Column col)	Implemented by users to process notifications on a Observer.ObservedColumn.

Method Detail

init

@Deprecated
default void init(Observer.Context context)
           throws Exception

Deprecated.

since 1.1.0. Fluo will no longer call this method when observers are configured by FluoConfiguration.setObserverProvider(String). Its only called when observers are configured the old way by FluoConfiguration.addObserver(org.apache.fluo.api.config.ObserverSpecification)

Implemented by user to initialize Observer.

Parameters:

context - Observer context

Throws:

Exception

process

void process(TransactionBase tx,
             Bytes row,
             Column col)
      throws Exception

Implemented by users to process notifications on a Observer.ObservedColumn. If a notification occurs, this method passes the user a TransactionBase as well as the row and Column where the notification occurred. The user can use the TransactionBase to read and write to Fluo. After this method returns, TransactionBase will be committed and closed by Fluo.

Throws:

Exception

getObservedColumn

@Deprecated
default Observer.ObservedColumn getObservedColumn()

Deprecated.

since 1.1.0 Fluo will no longer call this method when observers are configured by FluoConfiguration.setObserverProvider(String). Its only called when observers are configured the old way by FluoConfiguration.addObserver(org.apache.fluo.api.config.ObserverSpecification)

Implemented by user to return an Observer.ObservedColumn that will trigger this observer. During initialization, this information is stored in zookeeper so that workers have a consistent view. If a worker loads an Observer and the information returned differs from what is in zookeeper then an exception will be thrown. It is safe to assume that init(Context) will be called before this method. If the return value of the method is derived from what is passed to init(Context), then the derivation process should be deterministic.

close

@Deprecated
default void close()

Deprecated.

since 1.1.0. Fluo will no longer call this method when observers are configured by FluoConfiguration.setObserverProvider(String). Its only called when observers are configured the old way by FluoConfiguration.addObserver(org.apache.fluo.api.config.ObserverSpecification)

Implemented by user to close resources used by Observer