talk at London Perl Workshop 2008

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

2. Nestoria?

3. 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 …

5. Developers, not firefighters Bad Good

7. Documentation Bad: no documentation Worse: incorrect documentation

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

9. >./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

11. Measure twice, cut once

12. 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?

13. 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:

16. 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.

17. 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

18. Get help (cont.)

19. Help me to help you

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

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