Package org.objectweb.howl.log

Interface LogEventListener

All Known Implementing Classes:

XALogger

public interface LogEventListener

This interface is implemented by users of the Logger.

If a LogEventListener is registered, the logger will call the LogEventListener when interesting Log Events occur. For example, the Logger will notify the LogEventListener when the current log file is 50% full to allow the application to copy old log entries forward.

If the application does not register a LogEventListener it will not have visibility to Log events.

Field Summary

Fields

Modifier and Type	Field	Description
static final int	DEBUG	used to log low level events.
static final int	ERROR	used to log non-fatal error messages.
static final int	FATAL	used to log fatal error messages that should cause shutdown of the application using HOWL.
static final int	INFO	used to log information messages such as file open/close.
static final int	TRACE	used to trace method entry/exit and other low level events.
static final int	WARN	used to log warnings.

Method Summary

Modifier and Type	Method	Description
boolean	isLoggable(int level)	determine if log messages for requested level will be written to the log.
void	log(int level, String message)	write a log message to the event log.
void	log(int level, String message, Throwable thrown)	write a log message to the event log with exception information.
void	logOverflowNotification(long logkey)	Called by Logger to notify the LogEventListener that a log file overflow is approaching.

Field Details

TRACE

static final int TRACE

used to trace method entry/exit and other low level events.

See Also:

• Constant Field Values

DEBUG

static final int DEBUG

used to log low level events.

See Also:

• Constant Field Values

INFO

static final int INFO

used to log information messages such as file open/close.

See Also:

• Constant Field Values

WARN

static final int WARN

used to log warnings.

See Also:

• Constant Field Values

ERROR

static final int ERROR

used to log non-fatal error messages.

See Also:

• Constant Field Values

FATAL

static final int FATAL

used to log fatal error messages that should cause shutdown of the application using HOWL.

See Also:

• Constant Field Values

Method Details

logOverflowNotification

void logOverflowNotification(long logkey)

Called by Logger to notify the LogEventListener that a log file overflow is approaching.

Parameters:

logkey - lowest safe log key.

LogEventListener should cause log records with keys less than logkey to be copied forward to prevent a LogOverflowException.

Hopefully, the LogEventListener will be able to regenerate the records from memory without having to read the physical log file. For example, a Transaction Manager should maintain a table of transactions that are in the COMMITTING mode, with associated log key for each transaction. The logOverflowNotification method would call Logger.put() for each transaction that has a log key less than logKey .

Before returning from logOverflowNotification the LogEventListener should call Logger.mark(newMark, force) with force set to true to assure that the new records have been committed to physical disk.

isLoggable

boolean isLoggable(int level)

determine if log messages for requested level will be written to the log.

Returns:

true if the log level is being logged

See Also:

• invalid reference

  java.util.logging.Logger#isLoggable()

log

void log(int level,
 String message)

write a log message to the event log.

Parameters:

level - log level

message - text to be logged

log

void log(int level,
 String message,
 Throwable thrown)

write a log message to the event log with exception information.

Parameters:

level - log level

message - text to be logged

thrown - Throwable related to the event being logged.