io.pravega.client.state

Interface RevisionedStreamClient<T>

Type Parameters:

T - The type of data written.

All Superinterfaces:

AutoCloseable

public interface RevisionedStreamClient<T>
extends AutoCloseable

Provides a stream that can be read and written to with strong consistency. Each item read from the stream is accompanied by a Revision. These can be provided on write to guarantee that the writer is aware of all data in the stream. A specific location can also be marked, which can also be updated with strong consistency.

Method Summary

Modifier and Type	Method and Description
void	close() Closes the client and frees any resources associated with it.
boolean	compareAndSetMark(Revision expected, Revision newLocation) Records a provided location that can later be obtained by calling getMark().
Revision	fetchLatestRevision() Returns the latest revision.
Revision	fetchOldestRevision() Returns the oldest revision than can be read.
Revision	getMark() Returns a location previously set by compareAndSetMark(Revision, Revision).
Iterator<Map.Entry<Revision,T>>	readFrom(Revision start) Read from a specified revision to the end of the stream.
Revision	writeConditionally(Revision latestRevision, T value) If the supplied revision is the latest revision in the stream write the provided value and return the new revision.
void	writeUnconditionally(T value) Write a new value to the stream.

Method Detail

fetchOldestRevision

Revision fetchOldestRevision()

Returns the oldest revision than can be read.

Returns:

The oldest readable revision.

fetchLatestRevision

Revision fetchLatestRevision()

Returns the latest revision.

Returns:

Latest revision.

readFrom

Iterator<Map.Entry<Revision,T>> readFrom(Revision start)

Read from a specified revision to the end of the stream. The iterator returned will stop once it reaches the end of what was in the stream at the time this method was called.

Parameters:

start - The location the iterator should start at.

Returns:

An iterator over Revision, value pairs.

writeConditionally

Revision writeConditionally(Revision latestRevision,
                            T value)

If the supplied revision is the latest revision in the stream write the provided value and return the new revision. If the supplied revision is not the latest, nothing will occur and null will be returned.

Parameters:

latestRevision - The version to verify is the most recent.

value - The value to be written to the stream.

Returns:

The new revision if the data was written successfully or null if it was not.

writeUnconditionally

void writeUnconditionally(T value)

Write a new value to the stream.

Parameters:

value - The value to be written.

getMark

Revision getMark()

Returns a location previously set by compareAndSetMark(Revision, Revision).

Returns:

The marked location. (null if setMark was never been called)

compareAndSetMark

boolean compareAndSetMark(Revision expected,
                          Revision newLocation)

Records a provided location that can later be obtained by calling getMark(). Atomically set the mark to newLocation if it is the expected value.

Parameters:

expected - The expected value (May be null to indicate the mark is expected to be null)

newLocation - The new value

Returns:

true if it was successful. False if the mark was not the expected value.

close

void close()

Closes the client and frees any resources associated with it. (It may no longer be used)

Specified by:

close in interface AutoCloseable

See Also:

AutoCloseable.close()