In CFEngine's work directory there is a log file called promise_summary.log. Unsurprisingly, it contains a summary of how agent runs went in the past: how many promises were kept, how many repaired, and how many failed to be repaired. Some weeks ago a blog post on nanard.org showed how this file can be parsed to graph cfengine's activity, and I thought it could be a nice thing to do the same thing in Perl.

For those who never had a peek, the file looks like this:

bronto@murray:/var/cfengine$ tail promise_summary.log 
1367869877,1367869877: Outcome of version Community Failsafe.cf 1.0.0 (agent-0): Promises observed to be kept 95%, Promises repaired 0%, Promises not repaired 5%
1367869877,1367869905: Outcome of version MyOwnPC 1.0.16-1 (agent-0): Promises observed to be kept 97%, Promises repaired 3%, Promises not repaired 0%
1367870164,1367870164: Outcome of version Community Failsafe.cf 1.0.0 (agent-0): Promises observed to be kept 95%, Promises repaired 0%, Promises not repaired 5%
1367870164,1367870191: Outcome of version MyOwnPC 1.0.16-1 (agent-0): Promises observed to be kept 97%, Promises repaired 3%, Promises not repaired 0%
1367870450,1367870450: Outcome of version Community Failsafe.cf 1.0.0 (agent-0): Promises observed to be kept 95%, Promises repaired 0%, Promises not repaired 5%
1367870450,1367870475: Outcome of version MyOwnPC 1.0.16-1 (agent-0): Promises observed to be kept 97%, Promises repaired 3%, Promises not repaired 0%
1367870797,1367870797: Outcome of version Community Failsafe.cf 1.0.0 (agent-0): Promises observed to be kept 95%, Promises repaired 0%, Promises not repaired 5%
1367870797,1367870825: Outcome of version MyOwnPC 1.0.16-1 (agent-0): Promises observed to be kept 97%, Promises repaired 3%, Promises not repaired 0%
1367871083,1367871084: Outcome of version Community Failsafe.cf 1.0.0 (agent-0): Promises observed to be kept 95%, Promises repaired 0%, Promises not repaired 5%
1367871084,1367871111: Outcome of version MyOwnPC 1.0.16-1 (agent-0): Promises observed to be kept 97%, Promises repaired 3%, Promises not repaired 0%

The first thing, and I did it in some ten minutes, is to parse the file to extract the relevant information. Check this one-liner:

perl -F: -alne 'next if m{failsafe.cf}i ; my ($start,$finish) = split(",",$F[0],2) ; my $duration = $finish-$start ; my ($version) = m{version (.+) (} ; my ($kept,$rep,$notrep) = m{Promises observed to be kept (d+)%, Promises repaired (d+)%, Promises not repaired (d+)%} ; print join("t",$start,$duration,$version,$kept,$rep,$notrep)' promise_summary.log

Or, reformatted:

#!/usr/bin/perl -F: -aln

next if m{failsafe.cf}i ;

my ($start,$finish) = split(",",$F[0],2) ;
my $duration = $finish-$start ;
my ($version) = m{version (.+) (} ;
my ($kept,$rep,$notrep) = m{Promises observed to be kept (d+)%, Promises repaired (d+)%, Promises not repaired (d+)%} ;

print join("t",$start,$duration,$version,$kept,$rep,$notrep)

This parses the file and outputs the relevant information tab-separated.

The command line explained

• -a turns on the "autosplit" feature, where the input is split (normally at spaces) and the chunks are put in the @F array; in this specific case however, the "-F:" switch will make Perl split at colons ":";
• -l will make it so that newlines are added after each print;
• -n will wrap the code around a while loop, reading from the file(s) given as argument, and put each line in the $_ "default" variable;
• -e will execute the code given on the command line;

The code explained

• we skip the lines generated by the failsafe policy
• we split the first field (timestamps), and calculate the difference (that is: the duration of the run)
• we match the version string
• we match the percentage for kept, repaired, and not repaired promises;
• we print the bunch in tab-separated format

This is just the start, of course. E.g.: rather than tab-separated values one could print the values in a format suitable to rrdtool, and then use rrdgraph to create the graphs… But that's for later, take care for now. Ciao!