fabric.store
Class ReadHistory

java.lang.Object
  fabric.store.ReadHistory

public class ReadHistory
extends java.lang.Object

This class is responsible for keeping a log of the recent reads, for checking commit conflicts. Each read has a time associated with it, and the log only keeps the most recent entries.

Field Summary

static long

DEFAULT_LENGTH the default length of a read history, in milliseconds

Constructor Summary

ReadHistory()

ReadHistory(long length, long beginning)
create a new read history with duration length

Method Summary

boolean	check(long oid, long time) determine whether preparing an update to an object at a given time would cause a conflict with any reads that have occurred since that time.
void	record(PrepareRequest req) record a prepare request in the history

Methods inherited from class java.lang.Object

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

Field Detail

DEFAULT_LENGTH

public static final long DEFAULT_LENGTH

the default length of a read history, in milliseconds

See Also:

Constant Field Values

Constructor Detail

ReadHistory

public ReadHistory()

ReadHistory

public ReadHistory(long length,
                   long beginning)

create a new read history with duration length

Parameters:

length - the duration, in milliseconds, of entries in the history

beginning - a time such that no reads have happened since that time (typically now)

Method Detail

record

public void record(PrepareRequest req)

record a prepare request in the history

check

public boolean check(long oid,
                     long time)

determine whether preparing an update to an object at a given time would cause a conflict with any reads that have occurred since that time.

Parameters:

oid - the object to check

time - the commit time

Returns:

true if the object is safe to prepare