File::Write::Rotate - Write to files that archive/rotate themselves
This document describes version 0.22 of File::Write::Rotate (from Perl distribution File-Write-Rotate), released on 2014-09-01.
use File::Write::Rotate; my $fwr = File::Write::Rotate->new( dir => '/var/log', # required prefix => 'myapp', # required #suffix => '.log', # default is '' size => 25*1024*1024, # default is 10MB, unless period is set histories => 12, # default is 10 #buffer_size => 100, # default is none ); # write, will write to /var/log/myapp.log, automatically rotate old log files # to myapp.log.1 when myapp.log reaches 25MB. will keep old log files up to # myapp.log.12. $fwr->write("This is a line\n"); $fwr->write("This is", " another line\n"); # compress old log files $fwr->compress;
This module can be used to write to file, usually for logging, that can rotate itself. File will be opened in append mode. Locking will be done to avoid conflict when there are multiple writers. Rotation can be done by size (after a certain size is reached), by time (daily/monthly/yearly), or both.
I first wrote this module for logging script STDERR output to files (see Tie::Handle::FileWriteRotate).
Get or set buffer size. If set to a value larger than 0, then when a write() failed, instead of dying, the message will be stored in an internal buffer first (a regular Perl array). When the number of items in the buffer exceeds this size, then write() will die upon failure. Otherwise, every write() will try to flush the buffer.
Can be used for example when a program runs as superuser/root then temporarily drops privilege to a normal user. During this period, logging can fail because the program cannot lock the lock file or write to the logging directory. Before dropping privilege, the program can set buffer_size to some larger-than-zero value to hold the messages emitted during dropping privilege. The next write() as the superuser/root will succeed and flush the buffer to disk (provided there is no other error condition, of course).
Current file's path.
Current file handle. You should not use this directly, but use write() instead. This attribute is provided for special circumstances (e.g. in hooks, see example in the hook section).
Will be called by write() before actually writing to filehandle (but after locking is done). Code will be passed ($self, \@msgs, $fh) where @msgs is an array of strings to be written (the contents of buffer, if any, plus arguments passed to write()) and $fh is the filehandle.
Will be called by the rotating routine before actually doing rotating. Code will be passed ($self).
This can be used to write a footer to the end of each file, e.g.:
# hook_before_rotate my ($self) = @_; my $fh = $self->handle; print $fh "Some footer\n";
Since this hook is indirectly called by write(), locking is already done.
Will be called by the rotating routine after the rotating process. Code will be passed ($self, \@renamed, \@deleted) where @renamed is array of new filenames that have been renamed, @deleted is array of new filenames that have been deleted.
Will be called by after a new file is created. Code will be passed ($self).
This hook can be used to write a header to each file, e.g.:
# hook_after_create my ($self) = @_; my $fh $self->handle; print $fh "header\n";
Since this is called indirectly by write(), locking is also already done.
Create new object. Known arguments:
Directory to put the files in.
Name of files. The files will be named like the following:
<period> will only be given if the
period argument is set. If
period is set to
<period> will be
YYYY (4-digit year). If
<period> will be
YYYY-MM (4-digit year and 2-digit month). If
<period> will be
YYYY-MM-DD (4-digit year, 2-digit month, and 2-digit day).
<rotate_suffix> is either empty string for current file; or
.2 and so on for rotated files.
.1 is the most recent rotated file,
.2 is the next most recent, and so on.
An example, with
prefix set to
myapp # current file myapp.1 # most recently rotated myapp.2 # the next most recently rotated
prefix set to
period set to
suffix set to
myapp.2012-12.log # file name for december 2012 myapp.2013-01.log # file name for january 2013
Like previous, but additionally with
size also set (which will also rotate each period file if it exceeds specified size):
myapp.2012-12.log # file(s) for december 2012 myapp.2012-12.log.1 myapp.2012-12.log.2 myapp.2013-01.log # file(s) for january 2013
All times will use local time, so you probably want to set
TZ environment variable or equivalent methods to set time zone.
Suffix to give to file names, usually file extension like
prefix for more details.
If you use a yearly period, setting suffix is advised to avoid ambiguity with rotate suffix (for example, is
myapp.2012 the current file for year 2012 or file with
2012 rotate suffix?)
Maximum file size, in bytes, before rotation is triggered. The default is 10MB (10*1024*1024) if
period is not set. If
period is set, no default for
size is provided, which means files will not be rotated for size (only for period).
Can be set to either
yearly. If set, will automatically rotate after period change. See
prefix for more details.
Number of rotated files to keep. After the number of files exceeds this, the oldest one will be deleted. 0 means not to keep any history, 1 means to only keep
.1 file, and so on.
Set initial value of buffer. See the
buffer_size attribute for more information.
Write to file. Will automatically rotate file if period changes or file size exceeds specified limit. When rotating, will only keep a specified number of histories and delete the older ones. Uses locking, so multiple writers do not clobber one another. Lock file is named
.lck. Will wait for up to 1 minute to acquire lock, will die if failed to acquire lock.
Does not append newline so you'll have to do it yourself.
Compress old rotated files. Currently uses IO::Compress::Gzip to do the compression. Extension given to compressed file is
Will not lock writers, but will create
-compress.pid PID file to prevent multiple compression processes running and to signal the writers to postpone rotation.
After compression is finished, will remove the PID file, so rotation can be done again on the next
write() if necessary.
Mainly convenience and low maintenance. You no longer need a separate rotator like the Unix logrotate utility (which when accidentally disabled or misconfigured will cause your logs to stop being rotated and grow indefinitely).
Mainly performance overhead, as every write() involves locking to make it safe to use with multiple processes. Tested on my Core i5 3.1 GHz desktop, writing lines in the size of ~ 200 bytes, raw writing to disk (SSD) has the speed of around 3.4mil/s, while using FWR it comes down to around 19.5k/s.
However, this is not something you'll notice or need to worry about unless you're writing near that speed.
Perhaps an option to disable locking.
This makes FWR more general to use.
As a consequence of this, FWR does not support DatePattern; instead, FWR replaces it with a simple daily/monthly/yearly period.
Using separate processes like the Unix logrotate utility means having to deal with yet another race condition. FWR takes care of that for you (see the compress() method). You also have the option to do file compression in the same script/process if you want, which is convenient.
There is no significant overhead difference between FWR and LDFR (FWR is slightly faster than LDFR on my testing).
Please visit the project's homepage at https://metacpan.org/release/File-Write-Rotate.
Source repository is at https://github.com/perlancar/perl-File-Write-Rotate.
Please report any bugs or feature requests on the bugtracker website https://rt.cpan.org/Public/Dist/Display.html?Name=File-Write-Rotate
When submitting a bug or request, please include a test-file or a patch to an existing test-file that illustrates the bug or desired feature.
This software is copyright (c) 2014 by firstname.lastname@example.org.
This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.