Package org.apache.cassandra.hints

Class Hint

java.lang.Object

org.apache.cassandra.hints.Hint

public final class Hint
extends Object

Encapsulates the hinted mutation, its creation time, and the gc grace seconds param for each table involved. - Why do we need to track hint creation time? - We must exclude updates for tables that have been truncated after hint's creation, otherwise the result is data corruption. - Why do we need to track gc grace seconds? - Hints can stay in storage for a while before being applied, and without recording gc grace seconds (+ creation time), if we apply the mutation blindly, we risk resurrecting a deleted value, a tombstone for which had been already compacted away while the hint was in storage. We also look at the smallest current value of the gcgs param for each affected table when applying the hint, and use mutation creation time + min(recorded gc gs, current gcgs + current gc grace) as the overall hint expiration time. This allows now to safely reduce gc gs on tables without worrying that an applied old hint might resurrect any data.

Field Summary

Fields

Modifier and Type	Field	Description
static int	maxHintTTL
static final org.apache.cassandra.hints.Hint.Serializer	serializer

Method Summary

Modifier and Type	Method	Description
static Hint	create(Mutation mutation, long creationTime)
static Hint	create(Mutation mutation, long creationTime, int gcgs)
boolean	isLive()

Methods inherited from class java.lang.Object

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

Field Details

serializer

public static final org.apache.cassandra.hints.Hint.Serializer serializer

maxHintTTL

public static volatile int maxHintTTL

Method Details

create

public static Hint create(Mutation mutation,
 long creationTime)

Parameters:

mutation - the hinted mutation

creationTime - time of this hint's creation (in milliseconds since epoch)

create

public static Hint create(Mutation mutation,
 long creationTime,
 int gcgs)

isLive

public boolean isLive()

Returns:

calculates whether or not it is safe to apply the hint without risking to resurrect any deleted data