Mozilla Services - Week 22

What's this ? read this post.

What happened

I am getting ready for an important push today, that will switch some services under Python. Things are looking good.

On a side note: my fishes kept on dying in my aquarium and I finally found the problem by having the water analyzed. Thenice little river in my small town (175 people), that looks so clean, is basically saturated with Nitrates. I used it for my aquarium because I did not want to use tap water combined with some products to remove the chlorine. I thought I was helping out those poor fishes with nice river water, but I was killing them. This is insane.

Cross-team reviews

During the previous summit, we discuss at the MoPy meeting an interesting idea. What if people could ask for a code review from anyone from another team, that has the skills to do the review. I first thought about doing some kind of plugin for Bugzilla and have for every registered user a set of skillx, then propose a reviewer in the patch UI.

But that means people need to use the Bugzilla review process, and sometimes they use something else. I also wanted this review to be just an extra review with a low-commitment from the reviewers. In Bugzilla, if you are asked to review something, it will stay there waiting for your review for ever even if you don't review it. I don't think there's a way to timeout a review.

Last, cross-team review could be something broader than Mozilla teams. What about getting a review from someone in another Python project ?

Anyways, I started "Bug Brothers", a prototype to do this. There's a demo running here: http://bugbro.ziade.org and the code is here: https://bitbucket.org/tarek/bugbro. This was a good opportunity to try Pyramid, and yeah <blush> no tests and the code is not very clean.

It's not finished but it already allows people to ask for reviews, provide a link to a diff. When you review something you get credits, and when you ask for a review you pay credits. Everything is email-driven.

The next steps are to add more features like Rietveld. a tighter integration to Bugzilla, github. etc -- but without introducing a dependency to any tool so it can work for every team.

Mozilla Pulse

Coming from the Plone/Zope/Python world, I miss my checkins mailing lists in Mozilla projects. That is, getting a mail everytime a commit is done in one of the projects you work on. You can always read the Atom feeds in the various Mercurial repos, but that's not the same.

What I want is a diff in a mail can quickly look at. This is very useful to get instant reviews from other people. You usually catch more typos or mistakes. It also help initiating coding discussions.

Christian Legnitto has started the Mozilla Pulse project, which is exactly what I needed: a way to get notified on every change in the Mozilla eco-system. I was waiting for Pulse to get hooked in all our repos and this is now done.

The script to send e-mails on commits is very simple: https://bitbucket.org/tarek/services-pulse/src/tip/consumer.py. I need to add a diff view in the e-mail and a few options, but that's basically it. For now, it keeps only events happening in hg.mozila.org/services, and it will send e-mail to our services mailing list.

Overall, Pulse is a good way for anyone to watch a particular area in the Mozilla project

Stop guessing encodings

We had a bug in our Services code, related to a password containing an non-ascii character. It's a shame that as a French I did not insist on unicode vs str before. So here we go.

In Python 2 we have two types to deal with strings. We can use the str type or the unicode type. The str type is basically storing bytes so a string is encoded using a particular encoding, By default the encoding is ascii. The unicode type encodes strings as 16 or 32 bits integers and covers the unicode table. The most common error is to make no assumption whatsoever on the type of the string you get. What will happen is that some functions that need bytes will simply try to decode unicodes using the ascii coded, or vice-versa:

import base64

>>> def encode(data):

...     return base64.encodestring(data)

...

>>> encode('I am oke')

'SSBhbSBva2U=\n'

>>> encode(u'I am oké')

Traceback (most recent call last):

  File "<stdin>", line 1, in <module>

  File "<stdin>", line 2, in encode

  File "/usr/lib/python2.7/base64.py", line 315, in encodestring

    pieces.append(binascii.b2a_base64(chunk))

UnicodeEncodeError: 'ascii' codec can't encode character u'\xe9' in position 7: ordinal not in range(128)

One solution that comes in mind is to check for the type of the string in your function:

def encode(data):

...     if isinstance(data, unicode):

...         data = data.encode('utf8')

...     return base64.encodestring(data)

...

>>> encode(u'I am oké')

'SSBhbSBva8Op\n'

This is tempting but leads to another issue: if by default your program is able to deal with string or unicode for all your strings, there are high chances that you'll miss to check for the type somewhere or combine str and unicode in some places.

A much better approach is to use internally in your program only unicode and deal with conversions in inputs and outputs. In a Python web app it boils down to check that all inputs are unicode (beware of JSON).

The other issue is the encoding and the decoding. What codec should we use ? The asnswer is utf-8, because it's the most universal. To make sure there's no misunderstanding: a unicode is a decoded string, and a str is encoded. So you can decode() str and encode() unicode:

u'é'.encode('utf8')

'\xc3\xa9'

>>> 'é'.decode('utf8')

u'\xe9'

So, use only unicode in your apps, and when encoding, use the utf8 codec by default.

More on this here: http://docs.python.org/howto/unicode.html

What's next

  • More Python deployments
  • Some benches in the Sync server

Comments !