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

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

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

--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

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