Package com.mckoi.store

Class JournalledSystem

java.lang.Object

com.mckoi.store.JournalledSystem

class JournalledSystem
extends java.lang.Object

Manages a journalling data store management system. All operations are written out to a log that can be easily recovered from if a crash occurs.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
private class	JournalledSystem.AbstractResource	An abstract resource.
private static class	JournalledSystem.JournalEntry	A JournalEntry represents a modification that has been logging in the journal for a specific page of a resource.
private class	JournalledSystem.JournalFile	A JournalFile represents a file in which modification are logged out to when changes are made.
private class	JournalledSystem.JournalingThread	Thread that persists the journal in the backgroudn.
private static class	JournalledSystem.JournalSummary	Summary information about a journal.
private class	JournalledSystem.NonLoggingResource	An implementation of AbstractResource that doesn't log.
private class	JournalledSystem.Resource	Represents a resource in this system.

Field Summary

Fields

Modifier and Type	Field	Description
private java.util.HashMap	all_resources	The map of all resources that are available.
private DebugLogger	debug	A debug log to output information to.
private boolean	ENABLE_LOGGING	Set to true for logging behaviour.
private java.lang.Object	init_lock
private java.util.ArrayList	journal_archives	The archive of journal files currently pending (JournalFile).
private java.util.Comparator	journal_list_comparator
private long	journal_number	The current journal file number.
private java.io.File	journal_path	The path to the journal files.
private JournalledSystem.JournalingThread	journaling_thread	A thread that runs in the background and persists information that is in the journal.
private int	page_size	The page size.
private boolean	read_only	If the journal system is in read only mode.
private LoggingBufferManager.StoreDataAccessorFactory	sda_factory	A factory that creates StoreDataAccessor objects used to access the resource with the given name.
private long	seq_id	The unique sequence id counter for this session.
private JournalledSystem.JournalFile	top_journal_file	The current top journal file.
private java.lang.Object	top_journal_lock	Mutex when accessing the top journal file.

Constructor Summary

Constructors

Constructor	Description
JournalledSystem(java.io.File journal_path, boolean read_only, int page_size, LoggingBufferManager.StoreDataAccessorFactory sda_factory, DebugLogger debug, boolean enable_logging)

Method Summary

Modifier and Type	Method	Description
JournalledResource	createResource(java.lang.String resource_name)	Creates a resource.
private static java.lang.String	getJournalFileName(int number)	Returns a journal file name with the given number.
private JournalledSystem.AbstractResource	getResource(java.lang.String resource_name)	Returns the Resource with the given name.
private void	newTopJournalFile()	Creates a new top journal file.
(package private) void	rollForwardRecover()	Recovers any lost operations that are currently in the journal.
(package private) void	setCheckPoint(boolean flush_journals)	Sets a check point in the log.
(package private) void	start()	Starts the journal system.
(package private) void	stop()	Stops the journal system.
private JournalledSystem.JournalFile	topJournal()	Returns the current top journal file.

Methods inherited from class java.lang.Object

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

Field Detail

ENABLE_LOGGING

private final boolean ENABLE_LOGGING

Set to true for logging behaviour.

journal_path

private final java.io.File journal_path

The path to the journal files.

read_only

private final boolean read_only

If the journal system is in read only mode.

page_size

private final int page_size

The page size.

all_resources

private java.util.HashMap all_resources

The map of all resources that are available. (resource_name -> Resource)

seq_id

private long seq_id

The unique sequence id counter for this session.

journal_archives

private final java.util.ArrayList journal_archives

The archive of journal files currently pending (JournalFile).

top_journal_file

private JournalledSystem.JournalFile top_journal_file

The current top journal file.

journal_number

private long journal_number

The current journal file number.

sda_factory

private final LoggingBufferManager.StoreDataAccessorFactory sda_factory

A factory that creates StoreDataAccessor objects used to access the resource with the given name.

top_journal_lock

private final java.lang.Object top_journal_lock

Mutex when accessing the top journal file.

journaling_thread

private JournalledSystem.JournalingThread journaling_thread

A thread that runs in the background and persists information that is in the journal.

debug

private final DebugLogger debug

A debug log to output information to.

init_lock

private final java.lang.Object init_lock

journal_list_comparator

private java.util.Comparator journal_list_comparator

Constructor Detail

JournalledSystem

JournalledSystem(java.io.File journal_path,
                 boolean read_only,
                 int page_size,
                 LoggingBufferManager.StoreDataAccessorFactory sda_factory,
                 DebugLogger debug,
                 boolean enable_logging)

Method Detail

getJournalFileName

private static java.lang.String getJournalFileName(int number)

Returns a journal file name with the given number. The journal number must be between 10 and 63

start

void start()
    throws java.io.IOException

Starts the journal system.

Throws:

java.io.IOException

stop

void stop()
   throws java.io.IOException

Stops the journal system. This will persist any pending changes up to the last check point and then finish.

Throws:

java.io.IOException

rollForwardRecover

void rollForwardRecover()
                 throws java.io.IOException

Recovers any lost operations that are currently in the journal. This retries all logged entries. This would typically be called before any other IO operations.

Throws:

java.io.IOException

newTopJournalFile

private void newTopJournalFile()
                        throws java.io.IOException

Creates a new top journal file.

Throws:

java.io.IOException

topJournal

private JournalledSystem.JournalFile topJournal()

Returns the current top journal file.

createResource

public JournalledResource createResource(java.lang.String resource_name)

Creates a resource.

setCheckPoint

void setCheckPoint(boolean flush_journals)
            throws java.io.IOException

Sets a check point in the log. If 'flush_journals' is true then when the method returns we are guarenteed that all the journals are flushed and the data is absolutely current. If 'flush_journals' is false then we can't assume the journals will be empty when the method returns.

Throws:

java.io.IOException

getResource

private JournalledSystem.AbstractResource getResource(java.lang.String resource_name)

Returns the Resource with the given name.