org.corfudb.runtime.view.stream

Class AbstractStreamContext

java.lang.Object

org.corfudb.runtime.view.stream.AbstractStreamContext

All Implemented Interfaces:

Comparable<AbstractStreamContext>

public abstract class AbstractStreamContext
extends Object
implements Comparable<AbstractStreamContext>

A data class which keeps data for each stream context. Stream contexts represent a copy-on-write context - for each source stream a single context is used up until maxGlobalAddress, at which the new *destination* stream is used by popping the context off the stream context stack. Created by mwei on 1/6/17.

Field Summary

Fields

Modifier and Type	Field and Description
protected long	gcTrimMark The trim mark for Garbage Collection.
protected long	globalPointer A pointer to the current global address, which is the global address of the most recently added entry.

Constructor Summary

Constructors

Constructor and Description
AbstractStreamContext(UUID id, long maxGlobalAddress) Generate a new stream context given the id of the stream and the maximum address to read to.

Method Summary

Modifier and Type	Method and Description
int	compareTo(AbstractStreamContext o)
protected void	setGlobalPointer(long globalPointer)
protected void	setGlobalPointerCheckGCTrimMark(long globalPointer) Set Global Pointer and validate its position does not fall in the GC trim range.
protected void	validateGlobalPointerPosition(long globalPointer) Validate that Global Pointer position does not fall in the GC trim range.

Methods inherited from class java.lang.Object

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

Field Detail

gcTrimMark

protected long gcTrimMark

The trim mark for Garbage Collection. This is based on the log trim mark, and is used to discard data in the stream views before the trim mark. Note: Data cannot be discarded deliberately as there might be active transactions still operating in this space, we need to ensure the object is synced beyond this threshold before discarding data, or data might be temporarily loss or resets will slow performance.

globalPointer

protected long globalPointer

A pointer to the current global address, which is the global address of the most recently added entry.

Constructor Detail

AbstractStreamContext

public AbstractStreamContext(UUID id,
                             long maxGlobalAddress)

Generate a new stream context given the id of the stream and the maximum address to read to.

Parameters:

id - The id of the stream.

maxGlobalAddress - The maximum address to read up to.

Method Detail

setGlobalPointerCheckGCTrimMark

protected void setGlobalPointerCheckGCTrimMark(long globalPointer)

Set Global Pointer and validate its position does not fall in the GC trim range. If it falls we should throw a Trim Exception as this data no longer exists in the log and will be GC from all layers.

Parameters:

globalPointer - position to set the global pointer to.

setGlobalPointer

protected void setGlobalPointer(long globalPointer)

validateGlobalPointerPosition

protected void validateGlobalPointerPosition(long globalPointer)

Validate that Global Pointer position does not fall in the GC trim range. Note: we need to throw an exception whenever this is the case, as keeping active transactions in this range can lead to 'temporal' data loss when GC cycles ate started, i.e., sync to an old version and trimming the resolved queue, before the updates between old version and trim mark are applied to the object.

Parameters:

globalPointer - position to set the global pointer to.

compareTo

public int compareTo(AbstractStreamContext o)

Specified by:

compareTo in interface Comparable<AbstractStreamContext>