Grace JavaLog

Logging to Files

Grace Software

JavaLog

$Revision: 1.3 $

$Date: 2000/02/02 14:34:23 $

Logging to a File

JavaLog can log events to one or more files using the FileHandler class. To enable logging to a file, use the command line property:

    $ java -Dlog.handler.name.url=file:filename MyClass

This will cause JavaLog to write all events to filename. Here, filename can be either an absolute filename or a relative filename. Absolute files have a path prefix like /tmp/JavaLog/application.log. Relative paths have no path prefix like data/application.log and are relative to the current directory in which the java program is run.

Date Format in Filename

The filename may contain java.text.SimpleDateFormat characters like "%(simple-date-format). For example:

    -Dlog.handler.file.url="file:%(hh:mm:ss).log"

Limiting the file size

If the JavaLog program is a server, it will run for extended periods of time and could eventually create huge log files. JavaLog helps solve this problem by allowing the run time user to specify a maximum file size. When this maximum file size is exceeded, there are a few actions that can be performed. Currently the following actions may be performed:

Halve - The the last half of the file can be copied to new temporary file, and then copied back to the log file and logging continues. This is useful if one wants to make sure the log file occupies more than the maxsize bytes on the disk.
New - The current log file is closed and a new log file created. This is useful if one wants to archive log files. To use this effectively, one should embed SimpleDateFormat characters in the file specification so that the new filename is unique. It is also useful to use compression with this option.

For example:

    $ java -Dlog.handler.file.url="file:%(hh:mm:ss).log" -Dlog.handler.file.maxsize=1500k -Dlog.handler.file.maxsize.action=new MyClass

In the above example, a FileHandler is established (named "file") that will write to a file using the hour, minute, and second as its name with .log as the extension. It also configures the Handler to limit the file size to 1.5 megabytes and to create a new file each time the size limit is reached.

File Compression

When using log.handler.name.maxsize.action=new, JavaLog will close the current log file when the maxsize is reached and open a new one. At this time, the closed file can be compressed by specifying log.handler.name.compression=compression-type property. Here the compression-type can be zip, gzip, or zlib.

These compression types are assumed if the filename uses the extensions ".gz", ".zip", or ".z" respectively. So, the following example establishes a FileHandler to compress with gzip after the file reaches 1.5 megabytes:

    $ java -Dlog.handler.file.url="file:%(hh:mm:ss).gz" -Dlog.handler.file.maxsize=1500k MyClass

There are a few things to notice here:

The maxsize.action=new is is assumed because compression is used.
Events will be logged to a file called %(hh:mm:ss).log until the maxsize is reached. At that point the file will be compressed into %(hh:mm:ss).gz.