Planning for Debugging

Planning for debugging Ed Freyfogle London Perl Workshop 28 Nov. 2008

Nestoria?

What could go wrong? datasources Nestoria output Lots of data, many sources, 4 languges ETL, geocoding, deduplication …. HTML, whitelabels, API, widgets, FBML …. All with very few developers Internal tools, reporting, invoicing …

Developers, not firefighters Bad Good

Obvious first steps
Version Control
svn, trac
Build enviroment
local, staging, live
Tests
nightly, prelaunch, postlaunch

Documentation Bad: no documentation Worse: incorrect documentation

Who do you trust? You make mistakes. Computers don’t.

>./connect_to_database.pl --help Prints command needed to access database Usage: ./connect_to_database.pl --database [listings|searchindex] --country no default, (de|es|it|uk) --database type of DB --help --product_type default=realestate --type no default, (failover) --verbose Umm, the backup DB is on server 3, right? Don’t guess. Know

Logging
Make it easy to turn on/off
Log4Perl
Have cleanup strategy

Measure twice, cut once

my $script = ‘~/somescript.pl’; my $procs = determine_procs(); my $groups = some_test() ? 2 : 3; my $cmd = $script . ’ --groups ’ . $groups . ’ --procs ’ . $procs; system($cmd); Rome is burning. You have 10 seconds. What does this code do?

my $script = ‘~/somescript.pl’; my $procs = determine_procs(); my $groups = some_test() ? 2 : 3; my $cmd = $script . ’ --groups ’ . $groups . ’ --procs ’ . $procs; execute_cmd($cmd); sub execute_cmd{ my $cmd = shift; if ($dryrun){ print STDERR “would have run $cmd ”; } else { system($cmd); } } Better:

Don’t make me think
--help, --dryrun, --verbose
Getopt::Long
Term::ProgressBar

Invest now
schedule code review/learning
“ upgrade day”
keep an easy to edit list of ideas (wiki)
have an email/alerts strategy
CPAN is your friend
Perl::Metrics::Simple

Get help To: Nestoria team From: [email_address] Subject: Bug I think there is a bug. The page doesn’t seem to wrk. Pls fix.

Better To: Nestoria team From: [email_address] Subject: Bug I think there is a bug. The page doesn’t seem to wrk. Pls fix. HTTP_X_FORWARDED_FOR 81.136 .*.* SERVER_ADDR 10.10.*.* HTTP_USER_AGENT Mozilla/4.0 (compatible; MSIE 7.0; … Cookie MjEwREhQZ1JzeEl1NDAxMjIzNTY4MjE4A5A

Get help (cont.)

Help me to help you

Shameless plug Join us! You’ll love our API….

Questions? http://www.nestoria.co.uk http://blog.nestoria.co.uk

Planning for Debugging

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