Category: Rant

I am currently working on a new data source for the waypoint generator. Unfortunately because of the way it’s licensed, it’s only going to be for the iPhone version of CoPilot, and I can’t make it available for GPX and other users. Now all of my data loaders have, up until now, been written in Perl, and I have a really good Perl module that performs many of the loading tasks, such as merging existing data with new data.

The new data comes in the form of a gigantic XML file with a kind of weird schema. The provider actually provides both the gigantic file, and also a smaller set of updates on the 28 day cycle favoured by the ICAO, so hopefully I’ll only have to parse the gigantic file once, and then process the updates. I installed XML::SAX and Expat, and coded up a preliminary decoder to extract some (but not all) of the information that I need, just to make sure I was doing it right. I ran it with a subset of the data, and it seemed to be doing ok, and then just for grins while I was working on improving the code, I fired it off on the whole file. That was 3 days (72 hours) ago. It’s still running. Unfortunately I didn’t put in any progress messages so I don’t know where it is in file, only that it’s past the airport section that I care about. I profiled the subset data, and verified that Perl is spending most of its time in Perl code, not in native code – some of it mine, some of it XML::SAX, and some of it in Moose.

So here’s the conundrum: Do I spend the time to re-write this loader code in another language and hope it’s faster? Or do I accept the fact that this is going to take forever, but hopefully I’ll only have to do it once and then the updates will be small enough that I can do them in perl? Because re-writing in another language means re-writing all the data merging and validation logic code, and could be a potentially huge project. And I won’t know until it’s all working whether it’s going to be faster.

Update: I profiled the perl program with a semi-large dataset. Here’s the results:

dprofpp
Total Elapsed Time = 56.86461 Seconds
User+System Time = 46.10461 Seconds
Exclusive Times
%Time ExclSec CumulS #Calls sec/call Csec/c Name
20.5 9.494 23.288 397862 0.0000 0.0001 XML::SAX::Expat::_handle_start
15.4 7.136 12.820 131698 0.0000 0.0000 XML::SAX::Expat::_handle_char
14.7 6.787 55.922 1 6.7867 55.921 XML::Parser::Expat::ParseStream
13.6 6.311 12.977 397862 0.0000 0.0000 XML::SAX::Expat::_handle_end
7.07 3.258 3.258 472462 0.0000 0.0000 XML::NamespaceSupport::_get_ns_det
ails
6.79 3.132 3.132 397862 0.0000 0.0000 XML::NamespaceSupport::push_contex
t
6.48 2.986 5.685 131698 0.0000 0.0000 XML::SAX::Base::characters
4.24 1.953 1.953 131698 0.0000 0.0000 EADHandler::characters
3.87 1.786 4.411 397862 0.0000 0.0000 EADHandler::start_element
3.78 1.744 12.308 211270 0.0000 0.0000 XML::SAX::Base::__ANON__
3.69 1.702 1.838 4000 0.0004 0.0005 Data::Dumper::Dumpxs
2.55 1.174 5.870 397862 0.0000 0.0000 XML::SAX::Base::start_element
2.44 1.124 3.956 397862 0.0000 0.0000 XML::NamespaceSupport::process_ele
ment_name
1.93 0.892 0.892 397862 0.0000 0.0000 XML::NamespaceSupport::pop_context
1.85 0.854 5.768 397862 0.0000 0.0000 XML::SAX::Base::end_element

Note how it’s dominated by XML::SAX::Expat.

I’ve written a few times (here and here) about how every time you change something, every bug anywhere near that area now becomes your fault.

In my current job, I was in charge of a system called “Entitlements” that controlled who could do what and could access what parts of the system. Which means that dozens of new defects come to me with a note from the business analyst or equivalent person saying “looks like an Entitlement issue”. And I have to look at it and say “no, the reason they can’t access that part of the site isn’t because of Entitlements, it’s because NOBODY WROTE THAT PART OF THE SITE YET”.

Side note: we’re using “Agile Development”, which is a short form way of saying “we don’t know what the fuck we’re doing from day to day, and we’re not sure what has been done and what hasn’t until somebody complains that it’s not done”.

The good part is that because we’re Agile, that means when I discover that the problem is that nobody wrote that part of the site yet, I get to write it. So yay me.

I’ve written a few times in the past about idiots who get their monthly email reminders from my Mailman mailing lists and then write to me personally to unsubscribe instead of following the instructions in that email reminder.

For the last couple of months, somebody has been doing that, with a pissy “this is the [N]th request” just as a topper. I write back with “That email you got a few hours ago contains 3 different ways of unsubscribing yourself from the list, and nowhere is “writing a pissy email to the server administrator” listed as a viable option”. Unfortunately, in this case it turns out that the email address the guy is writing me from bounces. And it’s not subscribed to any of my mailing lists. So even if I wanted to unsubscribe him, I can’t.

So I guess I’ll just wait to see what “N” he gets to before he gets really mad. Not that I’ll be able to do anything about it. Or care, for that matter.