Sponsored Content
Top Forums Shell Programming and Scripting Rotating logs in Perl without message loss Post 302337449 by w1r3d on Friday 24th of July 2009 07:06:29 AM
Old 07-24-2009
Rotating logs in Perl without message loss

(I'm aware log rotation is a common subject, but I tried searching and couldn't find an answer)

For some time now, I've been using the Logfile::Rotate module to rotate logs in a log-monitoring script. So far, I haven't experienced any problems, and it works great because I can use it in Linux and Windows (mainly using Red Hat, and XP/2003). Well, it was brought to my attention by a co-worker that it is possible to lose log data using the "copy and truncate" method that the module uses. He mentioned that traditionally, in Linux, you do "move then send HUP signal to process". It seems like that is the preferred method (from what I see by searching online), but that would make it difficult for the script to port accross multiple OS's like it does now.

I guess my question is - what are your thoughts on this? I guess I thought this module worked perfectly, but this is the point he brings:

Code:
    ## copy current to next incremental
    $next = "${currn}.1";
    copy ($curr, $next);        

    ## preserve permissions and status
    if ( $self->{'Persist'} eq 'yes' ){
        my @stat = stat $curr;
        chmod( $stat[2], $next ) or carp "error: chmod failed: ($next)";
        utime( $stat[8], $stat[9], $next ) or carp "error: failed: ($next)";
        chown( $stat[4], $stat[5], $next ) or carp "error: chown failed: ($next)";
    }

    # now truncate the file
    if( $self->{'Flock'} eq 'yes' )
    {
        truncate $curr,0 or croak "error: could not truncate $curr: $!"; }
    else{
        local(*IN);
        open(IN, "+>$self->{'File'}") 
            or croak "error: could not truncate $curr: $!";
    }

The module does a "flock" on the file, which is an advisory lock on Linux. If the application that is writing to the current log file doesn't flock, then the flock on the rotation module is a no-op.

He mentioned that if the rotation module is task switched by the OS between the 'copy' on the third line and the 'truncate' or 'open' lines, log messages will be lost.

I am not very familiar with the way Linux works, and what I find online are mostly examples (code) of log rotation, and not actual explanations. Any insight on this subject will be greatly appreciated.

Thanks in advance!

edit: did some more testing, and was able to confirm (very minor) log loss with Linux's chatty auditd. I now have it so auditd rotates its own log files, and my script only monitors it. I'll have to come up with log file rotation schemes for all the different files I'm monitoring. Ugh. :-\

Last edited by w1r3d; 07-24-2009 at 08:56 AM..
 

9 More Discussions You Might Find Interesting

1. UNIX for Dummies Questions & Answers

Message Logs Error

I'm about 5 months new on an 5 year old unix system. If anyone can help me identify what causing the below errors i'd really appreciate it! unix: WARNING: /pci@1f,0/pci@1,1/ide@3/dad@1,0 (dad1): Uncorrectable data Error: Block 57e10 Unix: WARNING: /pci@1f,0/pci@1,1/ide@3/dad@1,0 (dad1):... (1 Reply)
Discussion started by: ByasB
1 Replies

2. UNIX for Advanced & Expert Users

ppp errror message in logs

I am getting this message in the log file. Apr 29 15:32:02 router ppp: Warning: Label COPYRIGHT rejected -direct connection: Configuration label not found This repeats every so often, the link is up however...Any ideas why i am getting this. Its freebsd 6.1 and pppoE. Frank (1 Reply)
Discussion started by: frankkahle
1 Replies

3. Shell Programming and Scripting

Perl script to rotate logs

I have a shell script that will gzip/tar/archive application logs that are over 20 days old which works just fine, but I would like to convert to a Perl script. Problem is, I'm a beginner with Perl and all attempts so far have failed. Basicaly I have a log dir /app/logs that contains several... (18 Replies)
Discussion started by: theninja
18 Replies

4. UNIX for Dummies Questions & Answers

Perl Scripting for monitoring logs

Hi, I am new to perl. I want to write a perl script to monitor logs. Where i want to monitor exceptions logged or any kind of error strings. I have a dir(On Solaris) with multiple log file which keeps rolling to .gz file after some time in that same dir. These logs files size keeps on... (1 Reply)
Discussion started by: solitare123
1 Replies

5. Shell Programming and Scripting

Concatenate Logs - Perl Question

Hi All, I am fresh to perl and had been using shell scripting in my past experiences. In my part of perl program, i am trying to run a application command ccm stop, which should give some string output as the result. The output (error or sucess) has to be returned to an exisiting log file.... (4 Replies)
Discussion started by: ganga.dharan
4 Replies

6. Shell Programming and Scripting

script to grep outofmemory message in logs

I have prepare script to grep for outofmemory messages in the logs. I need help in modifying script. I have implemented small logic. The outofmemory messages form six logs will store in variables. var1=`grep -i outofmemory $tomcat1logs | sed -n '$p'| sed -n -e "s/.*\(outofmemory\).*/\1/p"`... (6 Replies)
Discussion started by: coolguyamy
6 Replies

7. Shell Programming and Scripting

Pattern count on rotating logs for the past 1 Hr

Hi All, I have a requirement to write a shell script to search the logs in past 1 hour and extract some pattern from it and count it cumulatively to a file. The problem which I'm facing here is - logs rotates on size basis, say if size of log reaches 5 MB then new log will be generated and... (7 Replies)
Discussion started by: Gem_In_I
7 Replies

8. Shell Programming and Scripting

Unable to get full message text from Windows Event Logs

Hi all, . I am developing a log monitoring solution in perl for Windows I am using the CPAN module Win32 ::EventLog (0.076) version for getting the events from windows. The problem which I am facing now is all the Windows 2008 machines are upgraded with Service pack2 from then I couldn’t able... (2 Replies)
Discussion started by: kar_333
2 Replies

9. Shell Programming and Scripting

If I ran perl script again,old logs should move with today date and new logs should generate.

Appreciate help for the below issue. Im using below code.....I dont want to attach the logs when I ran the perl twice...I just want to take backup with today date and generate new logs...What I need to do for the below scirpt.............. 1)if logs exist it should move the logs with extention... (1 Reply)
Discussion started by: Sanjeev G
1 Replies
LOGROTATE(8)						   System Administrator's Manual					      LOGROTATE(8)

NAME
logrotate - rotates, compresses, and mails system logs SYNOPSIS
logrotate [-dv] [-f|--force] [-s|--state file] config_file+ DESCRIPTION
logrotate is designed to ease administration of systems that generate large numbers of log files. It allows automatic rotation, compres- sion, removal, and mailing of log files. Each log file may be handled daily, weekly, monthly, or when it grows too large. Normally, logrotate is run as a daily cron job. It will not modify a log multiple times in one day unless the criterium for that log is based on the log's size and logrotate is being run multiple times each day, or unless the -f or -force option is used. Any number of config files may be given on the command line. Later config files may override the options given in earlier files, so the order in which the logrotate config files are listed in is important. Normally, a single config file which includes any other config files which are needed should be used. See below for more information on how to use the include directive to accomplish this. If a directory is given on the command line, every file in that directory is used as a config file. If no command line arguments are given, logrotate will print version and copyright information, along with a short usage summary. If any errors occur while rotating logs, logrotate will exit with non-zero status. OPTIONS
-d Turns on debug mode and implies -v. In debug mode, no changes will be made to the logs or to the logrotate state file. -f, --force Tells logrotate to force the rotation, even if it doesn't think this is necessary. Sometimes this is useful after adding new entries to logrotate, or if old log files have been removed by hand, as the new files will be created, and logging will continue correctly. -m, --mail <command> Tells logrotate which command to use when mailing logs. This command should accept two arguments: 1) the subject of the message, and 2) the recipient. The command must then read a message on standard input and mail it to the recipient. The default mail command is /bin/mail -s. -s, --state <statefile> Tells logrotate to use an alternate state file. This is useful if logrotate is being run as a different user for various sets of log files. The default state file is /var/lib/logrotate/status. --usage Prints a short usage message. CONFIGURATION FILE
logrotate reads everything about the log files it should be handling from the series of configuration files specified on the command line. Each configuration file can set global options (local definitions override global ones, and later definitions override earlier ones) and specify a logfile to rotate. A simple configuration file looks like this: # sample logrotate configuration file compress /var/log/messages { rotate 5 weekly postrotate /sbin/killall -HUP syslogd endscript } "/var/log/httpd/access.log" /var/log/httpd/error.log { rotate 5 mail www@my.org size=100k sharedscripts postrotate /sbin/killall -HUP httpd endscript } /var/log/news/news.crit { monthly rotate 2 olddir /var/log/news/old missingok postrotate kill -HUP `cat /var/run/inn.pid` endscript nocompress } The first few lines set global options; in the example, logs are compressed after they are rotated. Note that comments may appear anywhere in the config file as long as the first non-whitespace character on the line is a #. The next section of the config files defined how to handle the log file /var/log/messages. The log will go through five weekly rotations before being removed. After the log file has been rotated (but before the old version of the log has been compressed), the command /sbin/killall -HUP syslogd will be executed. The next section defines the parameters for both /var/log/httpd/access.log and /var/log/httpd/error.log. They are rotated whenever is grows over 100k is size, and the old logs files are mailed (uncompressed) to www@my.org after going through 5 rotations, rather then being removed. The sharedscripts means that the postrotate script will only be run once, not once for each log which is rotated. Note that the double quotes around the first filename at the beginning of this section allows logrotate to rotate logs with spaces in the name. Normal shell quoting rules apply, with ', ", and characters supported. The last section defines the parameters for all of the files in /var/log/news. Each file is rotated on a monthly basis. This is considered a single rotation directive and if errors occur for more then one file, the log files are not compressed. Please use wildcards with caution. If you specify *, logrotate will rotate all files, including previously rotated ones. A way around this is to use the olddir directive or a more exact wildcard (such as *.log). Here is more information on the directives which may be included in a logrotate configuration file: compress Old versions of log files are compressed with gzip by default. See also nocompress. compresscmd Specifies which command to use to compress log files. The default is gzip. See also compress. uncompresscmd Specifies which command to use to uncompress log files. The default is gunzip. compressext Specifies which extension to use on compressed logfiles, if compression is enabled. The default follows that of the configured com- pression command. compressoptions Command line options may be passed to the compression program, if one is in use. The default, for gzip, is "-9" (maximum compres- sion). copy Make a copy of the log file, but don't change the original at all. This option can be used, for instance, to make a snapshot of the current log file, or when some other utility needs to truncate or pare the file. When this option is used, the create option will have no effect, as the old log file stays in place. copytruncate Truncate the original log file in place after creating a copy, instead of moving the old log file and optionally creating a new one, It can be used when some program can not be told to close its logfile and thus might continue writing (appending) to the previous log file forever. Note that there is a very small time slice between copying the file and truncating it, so some logging data might be lost. When this option is used, the create option will have no effect, as the old log file stays in place. create mode owner group Immediately after rotation (before the postrotate script is run) the log file is created (with the same name as the log file just rotated). mode specifies the mode for the log file in octal (the same as chmod(2)), owner specifies the user name who will own the log file, and group specifies the group the log file will belong to. Any of the log file attributes may be omitted, in which case those attributes for the new file will use the same values as the original log file for the omitted attributes. This option can be disabled using the nocreate option. daily Log files are rotated every day. delaycompress Postpone compression of the previous log file to the next rotation cycle. This has only effect when used in combination with com- press. It can be used when some program can not be told to close its logfile and thus might continue writing to the previous log file for some time. extension ext Log files are given the final extension ext after rotation. If compression is used, the compression extension (normally .gz) appears after ext. ifempty Rotate the log file even if it is empty, overiding the notifempty option (ifempty is the default). include file_or_directory Reads the file given as an argument as if it was included inline where the include directive appears. If a directory is given, most of the files in that directory are read in alphabetic order before processing of the including file continues. The only files which are ignored are files which are not regular files (such as directories and named pipes) and files whose names end with one of the taboo extensions, as specified by the tabooext directive. The include directive may not appear inside of a log file definition. mail address When a log is rotated out-of-existence, it is mailed to address. If no mail should be generated by a particular log, the nomail directive may be used. mailfirst When using the mail command, mail the just-rotated file, instead of the about-to-expire file. maillast When using the mail command, mail the about-to-expire file, instead of the just-rotated file (this is the default). missingok If the log file is missing, go on to the next one without issuing an error message. See also nomissingok. monthly Log files are rotated the first time logrotate is run in a month (this is normally on the first day of the month). nocompress Old versions of log files are not compressed with gzip. See also compress. nocopy Do not copy the original log file and leave it in place. (this overrides the copy option). nocopytruncate Do not truncate the original log file in place after creating a copy (this overrides the copytruncate option). nocreate New log files are not created (this overrides the create option). nodelaycompress Do not postpone compression of the previous log file to the next rotation cycle (this overrides the delaycompress option). nomail Don't mail old log files to any address. nomissingok If a log file does not exist, issue an error. This is the default. noolddir Logs are rotated in the same directory the log normally resides in (this overrides the olddir option). nosharedscripts Run prerotate and postrotate scripts for every script which is rotated (this is the default, and overrides the sharedscripts option). notifempty Do not rotate the log if it is empty (this overrides the ifempty option). olddir directory Logs are moved into directory for rotation. The directory must be on the same physical device as the log file being rotated. When this option is used all old versions of the log end up in directory. This option may be overriden by the noolddir option. postrotate/endscript The lines between postrotate and endscript (both of which must appear on lines by themselves) are executed after the log file is rotated. These directives may only appear inside of a log file definition. See prerotate as well. prerotate/endscript The lines between prerotate and endscript (both of which must appear on lines by themselves) are executed before the log file is rotated and only if the log will actually be rotated. These directives may only appear inside of a log file definition. See postro- tate as well. firstaction/endscript The lines between firstaction and endscript (both of which must appear on lines by themselves) are executed once before all log files that match the wildcarded pattern are rotated, before prerotate script is run and only if at least one log will actually be rotated. These directives may only appear inside of a log file definition. See lastaction as well. lastaction/endscript The lines between lastaction and endscript (both of which must appear on lines by themselves) are executed once after all log files that match the wildcarded pattern are rotated, after postrotate script is run and only if at least one log is rotated. These direc- tives may only appear inside of a log file definition. See lastaction as well. rotate count Log files are rotated <count> times before being removed or mailed to the address specified in a mail directive. If count is 0, old versions are removed rather then rotated. size size Log files are rotated when they grow bigger then size bytes. If size is followed by M, the size if assumed to be in megabytes. If the k is used, the size is in kilobytes. So size 100, size 100k, and size 100M are all valid. sharedscripts Normally, prescript and postscript scripts are run for each log which is rotated, meaning that a single script may be run multiple times for log file entries which match multiple files (such as the /var/log/news/* example). If sharedscript is specified, the scripts are only run once, no matter how many logs match the wildcarded pattern. However, if none of the logs in the pattern require rotating, the scripts will not be run at all. This option overrides the nosharedscripts option. start count This is the number to use as the base for rotation. For example, if you specify 0, the logs will be created with a .0 extension as they are rotated from the original log files. If you specify 9, log files will be created with a .9, skipping 0-8. Files will still be rotated the number of times specified with the count directive. tabooext [+] list The current taboo extension list is changed (see the include directive for information on the taboo extensions). If a + precedes the list of extensions, the current taboo extension list is augmented, otherwise it is replaced. At startup, the taboo extension list contains .rpmorig, .rpmsave, ,v, .swp, .rpmnew, and ~. weekly Log files are rotated if the current weekday is less then the weekday of the last rotation or if more then a week has passed since the last rotation. This is normally the same as rotating logs on the first day of the week, but it works better if logrotate is not run every night. FILES
/var/lib/logrotate/status Default state file. /etc/logrotate.conf Configuration options. SEE ALSO
gzip(1) AUTHORS
Erik Troan <ewt@redhat.com> Preston Brown <pbrown@redhat.com> 4th Berkeley Distribution Wed Nov 5 2002 LOGROTATE(8)
All times are GMT -4. The time now is 05:01 AM.
Unix & Linux Forums Content Copyright 1993-2022. All Rights Reserved.
Privacy Policy