org.apache.river.outrigger

Class OperationJournal

java.lang.Object

java.lang.Thread

org.apache.river.outrigger.OperationJournal

All Implemented Interfaces:

Runnable

class OperationJournal
extends Thread

Maintain a journal of operations on entries (writes, takes, and resolution of locks) and a thread that will process the journal. This journal is kept for three reasons. One is so events can be generated asynchronously from the writes and transaction commits that cause them. Second so blocked queries can be alerted to changes that will allow them to be resolved.

Third to make sure that transitions occur between the time a query starts its initial search and the time it adds its watcher to the TransitionWatchers object do not get missed. This last goal is accomplished by queries calling newTransitionIterator before initial search, doing the initial search, adding their watcher to the TransitionWatchers object and then calling watcherRegistered on the TransitionIterator and then feeding their watcher the chain of transitions yielded by the TransitionIterator. (skipping any transitions with entries that don't match).

Each operation that is recored in the journal is assigned an ordinal. Operations with higher ordinals must be considered to have taken place after operations with lower ordinals.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
private static class	OperationJournal.CaughtUpMarker JournalNode payload value used for caught up markers.
private class	OperationJournal.JournalNode The nodes of our Journal
(package private) class	OperationJournal.TransitionIterator An iterator that will yield (in the order they were posted) all the EntryTransitions added after the iterator was created and processed before watcherRegistered was called.

Nested classes/interfaces inherited from class java.lang.Thread

Thread.State, Thread.UncaughtExceptionHandler

Field Summary

Fields

Modifier and Type	Field and Description
private boolean	dead If true stop thread
private java.util.concurrent.atomic.AtomicLong	lastOrdinalUsed The last ordinal value used
private OperationJournal.JournalNode	lastProcessed The JournalNode we are currently processing or if none are in process the last one we processed.
private static Logger	logger Logger for logging exceptions
private OperationJournal.JournalNode	tail The current tail of the transitions list.
private TransitionWatchers	watchers The object to ask about who is interested in a transition

Fields inherited from class java.lang.Thread

MAX_PRIORITY, MIN_PRIORITY, NORM_PRIORITY

Constructor Summary

Constructors

Constructor and Description
OperationJournal(TransitionWatchers watchers) Create a new OperationJournal.

Method Summary

Modifier and Type	Method and Description
(package private) long	currentOrdinal() Return the ordinal of the last operation posted.
private OperationJournal.JournalNode	lastProcessed(OperationJournal.JournalNode noEarlierThan) Return the node currently being processed, or if no entry is currently being processed the last one that was processed.
(package private) void	markCaughtUp(IfExistsWatcher watcher) Schedules a job that will call the caughtUp method on the passed IfExistsWatcher after the last posted EntryTransition is processed.
(package private) OperationJournal.TransitionIterator	newTransitionIterator() Return an iterator that can latter be used to get all the EntryTransitions added after this point that have been processed.
private void	post(OperationJournal.JournalNode node) Post a JournalNode
(package private) void	recordTransition(EntryTransition transition) Records an operation on an entry.
void	run() Loop pulling transitions off the queue and process them by getting the set of interested watchers from the TransitionWatchers object associated with this object and then calling process on each of the watchers.
(package private) void	terminate() Terminate queue processing.

Methods inherited from class java.lang.Thread

activeCount, checkAccess, clone, countStackFrames, currentThread, destroy, dumpStack, enumerate, getAllStackTraces, getContextClassLoader, getDefaultUncaughtExceptionHandler, getId, getName, getPriority, getStackTrace, getState, getThreadGroup, getUncaughtExceptionHandler, holdsLock, interrupt, interrupted, isAlive, isDaemon, isInterrupted, join, join, join, resume, setContextClassLoader, setDaemon, setDefaultUncaughtExceptionHandler, setName, setPriority, setUncaughtExceptionHandler, sleep, sleep, start, stop, stop, suspend, toString, yield

Methods inherited from class java.lang.Object

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

Field Detail

watchers

private final TransitionWatchers watchers

The object to ask about who is interested in a transition

tail

private volatile OperationJournal.JournalNode tail

The current tail of the transitions list.

lastProcessed

private volatile OperationJournal.JournalNode lastProcessed

The JournalNode we are currently processing or if none are in process the last one we processed.

dead

private volatile boolean dead

If true stop thread

lastOrdinalUsed

private final java.util.concurrent.atomic.AtomicLong lastOrdinalUsed

The last ordinal value used

logger

private static final Logger logger

Logger for logging exceptions

Constructor Detail

OperationJournal

OperationJournal(TransitionWatchers watchers)

Create a new OperationJournal.

Parameters:

watchers - Set of watchers that need to be asked if they are interested in the transitions.

Throws:

NullPointerException - if watchers is null.

Method Detail

recordTransition

void recordTransition(EntryTransition transition)

Records an operation on an entry. This method should be called after the transition has been made visible in contents (including any subsidiary objects such as the appropriate EntryHandle).

Parameters:

transition - an object describing the visibility transition of an entry.

Throws:

NullPointerException - if transition is null.

markCaughtUp

void markCaughtUp(IfExistsWatcher watcher)

Schedules a job that will call the caughtUp method on the passed IfExistsWatcher after the last posted EntryTransition is processed.

Parameters:

watcher - The watcher to notify when it is caught up.

Throws:

NullPointerException - if watcher is null.

currentOrdinal

long currentOrdinal()

Return the ordinal of the last operation posted. Any operations with a higher ordinal should be considered to have taken place after this point in time.

Returns:

the ordinal of the last operation posted.

post

private void post(OperationJournal.JournalNode node)

Post a JournalNode

Parameters:

node - The node to post.

newTransitionIterator

OperationJournal.TransitionIterator newTransitionIterator()

Return an iterator that can latter be used to get all the EntryTransitions added after this point that have been processed.

We synchronize to make sure the initial state of the returned transition has been fetched from main memory.

Returns:

An iterator that can latter be used to get all the EntryTransitions added after this point that have been processed.

lastProcessed

private OperationJournal.JournalNode lastProcessed(OperationJournal.JournalNode noEarlierThan)

Return the node currently being processed, or if no entry is currently being processed the last one that was processed. A watcher that was added to the TransitionWatchers object associated with this object before this call was made is guaranteed to be asked by the journal about any transition posted after the node returned by this method was posted.

Parameters:

noEarlierThan - The returned JournalNode is guaranteed to have not been posted before noEarlierThan. If the last node processes was posted before noEarlierThan, then noEarlierThan will be returned.

Returns:

The last node that has been at least partially processed.

terminate

void terminate()

Terminate queue processing.

run

public void run()

Loop pulling transitions off the queue and process them by getting the set of interested watchers from the TransitionWatchers object associated with this object and then calling process on each of the watchers.

Specified by:

run in interface Runnable

Overrides:

run in class Thread