io.atomix.copycat.server.storage.compaction

Class MinorCompactionTask

java.lang.Object

io.atomix.copycat.server.storage.compaction.MinorCompactionTask

All Implemented Interfaces:

CompactionTask, Runnable

public final class MinorCompactionTask
extends Object
implements CompactionTask

Removes released entries from an individual log Segment to reclaim disk space.

The minor compaction task is a lightweight process that rewrites an individual segment to remove entries for that do not have to be removed sequentially from the log.

When a segment is rewritten by the minor compaction task, a new compact segment is created with the same starting index as the segment being compacted and the next greatest version number. The version number allows the SegmentManager to account for failures during log compaction when recovering the log from disk. If a failure occurs during minor compaction, the segment manager will attempt to load the segment with the greatest version for a given range of entries from disk. If the segment with the greatest version did not finish compaction, it will be discarded and the old segment will be used. Once the minor compaction task is done rewriting a segment, it will SegmentDescriptor.lock() the segment to indicate that the segment has completed compaction and is safe to read, and the compacted segment will be made available to the Log.

Author:

Method Summary

Modifier and Type	Method and Description
void	run()
String	toString()

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

Method Detail

run

public void run()

Specified by:

run in interface Runnable

toString

public String toString()

Overrides:

toString in class Object