org.corfudb.runtime.view.stream

Class AbstractContextStreamView<T extends AbstractStreamContext>

java.lang.Object

org.corfudb.runtime.view.stream.AbstractContextStreamView<T>

All Implemented Interfaces:

AutoCloseable, Iterator<ILogData>, IStreamView

Direct Known Subclasses:

AbstractQueuedStreamView

public abstract class AbstractContextStreamView<T extends AbstractStreamContext>
extends Object
implements IStreamView, AutoCloseable

An abstract context stream view maintains contexts, which are used to implement copy-on-write entries.

This implementation uses "contexts" to properly deal with copy-on-write streams. Every time a stream is copied, a new context is created which redirects requests to the source stream for the copy - each context contains its own queue and pointers. Implementers of fillReadQueue() and readAndUpdatePointers should be careful to use the id of the context, rather than that of the stream view itself.

Created by mwei on 1/6/17.

Nested Class Summary

Nested classes/interfaces inherited from interface org.corfudb.runtime.view.stream.IStreamView

IStreamView.SearchDirection

Constructor Summary

Constructors

Constructor and Description
AbstractContextStreamView(CorfuRuntime runtime, UUID id, BiFunction<UUID,Long,T> contextFactory) Create a new abstract context stream view.

Method Summary

Modifier and Type	Method and Description
void	close()
protected boolean	doesEntryUpdateContext(ILogData data) Check whether the given entry updates the context.
protected T	getCurrentContext() Get the current context.
protected abstract boolean	getHasNext(T context) Return whether calling getNextEntry() may return more entries, given the context.
protected List<ILogData>	getNextEntries(T context, long maxGlobal, Function<ILogData,Boolean> contextCheckFn) Retrieve the next entries in the stream, given the context.
protected abstract ILogData	getNextEntry(T context, long maxGlobal) Retrieve the next entry in the stream, given the context.
boolean	hasNext() Returns whether or not there are potentially more entries in this stream - this function may return true even if there are no entries remaining, as addresses may have been acquired by other clients but not written yet, or the addresses were hole-filled, or just failed.
ILogData	nextUpTo(long maxGlobal) Retrieve the next entry from this stream, up to the address given or the tail of the stream.
protected void	popContext()
protected boolean	processEntryForContext(ILogData data) Check if the given entry adds a new context, and update the global pointer.
protected void	pushNewContext(UUID id, long maxGlobal) Add a new context.
List<ILogData>	remainingUpTo(long maxGlobal) Retrieve all of the entries from this stream, up to the address given or the tail of the stream.
void	reset() Reset the state of this stream view, causing the next read to start from the beginning of this stream.
void	seek(long globalAddress) Seek to the requested maxGlobal address.
String	toString()

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.corfudb.runtime.view.stream.IStreamView

append, append, current, find, gc, getCurrentGlobalPosition, getId, getTotalUpdates, next, previous, remaining, spliterator, spliteratorUpTo, stream, streamUpTo

Methods inherited from interface java.util.Iterator

forEachRemaining, remove

Constructor Detail

AbstractContextStreamView

public AbstractContextStreamView(CorfuRuntime runtime,
                                 UUID id,
                                 BiFunction<UUID,Long,T> contextFactory)

Create a new abstract context stream view.

Parameters:

runtime - The runtime.

id - The id of the stream.

contextFactory - A function which generates a context, given the stream id and a maximum global address.

Method Detail

reset

public void reset()

Reset the state of this stream view, causing the next read to start from the beginning of this stream.

Specified by:

reset in interface IStreamView

seek

public void seek(long globalAddress)

Seek to the requested maxGlobal address. The next read will begin at the given global address, inclusive.

Specified by:

seek in interface IStreamView

Parameters:

globalAddress - Address to seek to

close

public void close()

Specified by:

close in interface AutoCloseable

nextUpTo

public final ILogData nextUpTo(long maxGlobal)

Retrieve the next entry from this stream, up to the address given or the tail of the stream. If there are no entries present, this function will return NULL. If there are holes present in the log, they will be filled.

Specified by:

nextUpTo in interface IStreamView

Parameters:

maxGlobal - The maximum global address to read up to.

Returns:

The next entry in the stream, or NULL, if no entries are available.

remainingUpTo

public final List<ILogData> remainingUpTo(long maxGlobal)

Retrieve all of the entries from this stream, up to the address given or the tail of the stream. If there are no entries present, this function will return an empty list. If there are holes present in the log, they will be filled.

Specified by:

remainingUpTo in interface IStreamView

Parameters:

maxGlobal - The maximum global address to read up to.

Returns:

The next entries in the stream, or an empty list, if no entries are available.

hasNext

public boolean hasNext()

Returns whether or not there are potentially more entries in this stream - this function may return true even if there are no entries remaining, as addresses may have been acquired by other clients but not written yet, or the addresses were hole-filled, or just failed.

Specified by:

hasNext in interface Iterator<ILogData>

Specified by:

hasNext in interface IStreamView

Returns:

True, if there are potentially more entries in the stream.

getHasNext

protected abstract boolean getHasNext(T context)

Return whether calling getNextEntry() may return more entries, given the context.

Parameters:

context - The context to retrieve the next entry from.

Returns:

True, if getNextEntry() may return an entry. False otherwise.

getNextEntry

protected abstract ILogData getNextEntry(T context,
                                         long maxGlobal)

Retrieve the next entry in the stream, given the context.

Parameters:

context - The context to retrieve the next entry from.

maxGlobal - The maximum global address to read to.

Returns:

Next ILogData for this context

getNextEntries

protected List<ILogData> getNextEntries(T context,
                                        long maxGlobal,
                                        Function<ILogData,Boolean> contextCheckFn)

Retrieve the next entries in the stream, given the context.

This function is designed to implement a bulk read. In a bulk read, one of the entries may cause the context to change - the implementation should check if the entry changes the context and stop reading if this occurs, returning the entry that caused contextCheckFn to return true.

The default implementation simply calls getNextEntry.

Parameters:

context - The context to retrieve the next entry from.

maxGlobal - The maximum global address to read to.

contextCheckFn - A function which returns true if the entry changes the stream context.

Returns:

A list of the next entries for this context

doesEntryUpdateContext

protected boolean doesEntryUpdateContext(ILogData data)

Check whether the given entry updates the context.

Parameters:

data - The entry to check.

Returns:

True, if the entry will update the context.

processEntryForContext

protected boolean processEntryForContext(ILogData data)

Check if the given entry adds a new context, and update the global pointer.

If it does, add it to the context stack. Otherwise, pop the context.

It is important that this method be called in order, since it updates the global pointer and can change the global pointer.

Parameters:

data - The entry to process.

Returns:

True, if this entry adds a context.

getCurrentContext

protected T getCurrentContext()

Get the current context.

Should never throw a NoSuchElement exception because streamContexts should always at least have one element.

pushNewContext

protected void pushNewContext(UUID id,
                              long maxGlobal)

Add a new context.

popContext

protected void popContext()

toString

public String toString()

Overrides:

toString in class Object