Archiv für Mai 2012

Apport API users: Watch your data types / Python 3 porting

I just uploaded Apport 2.1 to Quantal. A big change in that version is that the whole code now works with both Python 2 and 3, except for the launchpadlib crash database backend (as we do not yet have a python3-launchpadlib package).

I took some care that apport report objects get along with both strings (unicode type in Python 2) and byte arrays (str type in Python 2) in values, so most package hooks should still work. However, now is the time to check whether they also work with Python 3, to make the impending transition to Python 3 easier.

However, you need to watch out if you use projects or scripts which directly use python-apport to process reports: The open(), write(), and write_mime() methods now require the passed file descriptors to be open in binary mode. You will get an exception otherwise.

A common pattern so far has been code like

  report = apport.Report()
  report.load(open('myfile.crash'))

This needs to be changed to

  report = apport.Report()
  with open('myfile.crash', 'rb') as f:
      report.load(f)

The “with” context is not strictly required, but it takes care of timely closing the files again. This avoids ResourceWarning spew when you run this in test suites or enable warnings.

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To boldly go where no test has gone before

As I wrote two weeks ago, I consider the QA related changes in Ubuntu 12.04 a great success. But while we will continue and even extend our efforts there, this is not where the ball stops: it’s great to have the feedback cycle between “break it” and “notice the bug” reduced from potentially a few months to one day in many cases, but wouldn’t it be cool to reduce that to a few minutes, and also put the machinery right at where stuff really happens — into the upstream trunks? If for every commit to PyGObject, GTK, NetworkManager, udisks, D-BUS, telepathy, gvfs, etc. we’d immediately build and test all reverse dependencies and the committer would be told about regressions?

I have had the desire to work on automated tests in Linux Plumbing and GNOME for quite a while now. Also, after 8 years of doing distribution work of packaging and processes (tech lead, release engineering/management, stable release updates, etc.) I wanted to shift my focus towards technology development. So I’ve been looking for a new role for some time now.

It seems that time is finally there: At the recent UDS, Mark announced that we will extend our QA efforts to upstream. I am very happy that in two weeks I can now move into a role to make this happen: Developing technology to make testing easier, work with our key upstreams to set up test suites and reporting, and I also can do some general development in areas that are near and dear to my heart, like udev/systemd, udisks, pygobject, etc. This work will be following the upstream conventions for infrastructure and development policies. In particular, it is not bound by Canonical copyright license agreements.

I have a bunch of random ideas what to work on, such as:

  • Making it possible/easier to write tests with fake hardware. E. g. in the upower integration tests that I wrote a while ago there is some code to create a fake sysfs tree which should really go into udev itself, available from C and introspection and be greatly extended. Also, it’s currently not possible to simulate a uevent that way, that’s something I’d like to add. Right now you can only set up /sys, start your daemon, and check the state after the coldplugging phase.
  • Interview some GNOME developers what kind of bugs/regressions/code they have most trouble with and what/how they would like to test. Then write a test suite with a few working and one non-working case (bugzilla should help with finding these), discuss the structure with the maintainer again, find some ways to make the tests radically simpler by adding/enhancing the API available from gudev/glib/gtk, etc. E. g. in the tests for apport-gtk I noticed that while it’s possible to do automatic testing of GUI applications it is still way harder than it should and needs to be. I guess that’s the main reason why there are hardly any GUI tests in GNOME?
  • I’ve heard from several people that it would be nice to be able to generate some mock wifi/ethernet/modem adapters to be able to automatically test NetworkManager and the like. As network devices are handled specially in Linux, not in the usual /dev and sysfs manner, they are not easy to fake. It probably needs a kernel module similar to scsi_debug, which fakes enough of the properties and behaviour of particular nmetwork card devices to be useful for testing. One could certainly provide a pipe or a regular bridge device at the other end to actually talk to the application through the fake device. (NB this is just an idea, I haven’t looked into details at all yet).
  • For some GUI tests it would be much easier if there was a very simple way of providing mocks/stubs for D-BUS services like udisks or NetworkManager than having to set up the actual daemons, coerce them into some corner-case behaviour, and needing root privileges for the test due to that. There seems to be some prior art in Ruby, but I’d really like to see this in D-BUS itself (perhaps a new library there?), and/or having this in GDBus where it would even be useful for Python or JavaScript tests through gobject-introspection.
  • There are nice tools like the Clang static code analyzer out there. I’d like to play with those and see how we can use it without generating a lot of false positives.
  • Robustify jhbuild to be able to keep up with building everything largely unattended. Right now you need to blow away and rebuild your tree way too often, due to brittle autotools or undeclared dependencies, and if we want to run this automatically in Jenkins it needs to be able to recover by itself. It should be able to keep up with the daily development, automatically starting build/test jobs for all reverse dependencies for a module that just has changed (and for basic libraries like GLib or GTK that’s going to be a lot), and perhaps send out mail notifications when a commit breaks something else. This also needs some discussion first, about how/where to do the notifications, etc.

Other ideas will emerge, and I hope lots of you have their own ideas what we can do. So please talk to me! We’ll also look for a second person to work in that area, so that we have some capacity and also the possibility to bounce ideas and code reviews between each other.

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Debian/Ubuntu Packages for PostgreSQL 9.2 Beta 1

The first Beta of the upcoming PostgreSQL 9.2 was released yesterday (see announcement). Your humble maintainer has now created packages for you to test. Please give them a whirl, and report any problems/regressions that you may see to the PostgreSQL developers, so that we can have a rock solid 9.2 release.

Remember, with the postgresql-common infrastructure you can use pg_upgradecluster to create a 9.2 cluster from your existing 8.4/9.1 cluster and run them both in parallel without endangering your data.

For Debian the package is currently waiting in the NEW queue, I expect them to go into experimental in a day or two. For Ubuntu 12.04 LTS you can get packages from my usual PostgreSQL backports PPA. Note that you need at least postgresql-common version 0.130, which is available in Debian unstable and the PPA now.

I (or rather, the postgresql-common test suite) found one regression: Upgrades do not keep the current value of sequences, but reset them to their default value. I reported this upstream and will provide updated packages as soon as this is fixed.

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PyGObject 3.3.1 released

This announcement comes very late (a week after release), but better late than never..

The first PyGObject 3.3 series release is now out, with lots of yummy fixes and improvements. Dieter, Sebastian, and I went through a round of bugzilla spring cleaning to clean up old bugs, fix simple bugs, and apply good patches that were waiting, so as a result the patch queue is now almost empty and PyGObject works better than ever.

There was also quite some work on the test suite: it became a lot stricter and robust, and now also enforces PEP8 compatibility and absence of pyflake errors of the code.

One small but handy new feature is that the freeze_notify() and handler_block() methods are now context managers, i. e. they automatically call the corresponding thaw_notify()/handler_unblock() at the end of the with statement in an exception-safe way. ((#672324)

There are almost no API changes in this release, so it should work fine with GNOME 3.4 and applications developed with pygobject 3.2. The one exception is the removal of the Gobject.get_data() and Gobject.set_data() methods. They were prone to errors and crashes as they are not safely bindable, and in Python you can and should just use normal Python object attributes instead.

Complete list of changes:

  • GSettings: allow extra keyword arguments (Giovanni Campagna) (#675105)
  • pygtkcompat: Correct Userlist module use (Jose Rostagno) (#675084)
  • Add release-news make rule (Martin Pitt)
  • Add “make check.nemiver” target (Martin Pitt)
  • Test flags and enums in GHash values (Martin Pitt) (#637466)
  • tests: Activate test_hash_in and apply workaround (Martin Pitt) (#666636)
  • Add special case for Gdk.Atom array entries from Python (Martin Pitt) (#661709)
  • test_gdbus: Call GetConnectionUnixProcessID() with correct signature (Martin Pitt) (#667954)
  • Add test case for Gtk.ListStore custom sort (Martin Pitt) (#674475)
  • GTK overrides: Add missing keyword arguments (Martin Pitt) (#660018)
  • Add missing override for TreeModel.iter_previous() (Martin Pitt) (#660018)
  • pygi-convert.py: Drop obsolete drag method conversions (Martin Pitt) (#652860)
  • tests: Replace deprecated assertEquals() with assertEqual() (Martin Pitt)
  • Plug tiny leak in constant_info_get_value (Paolo Borelli) (#642754)
  • Fix len_arg_index for array arguments (Bastian Winkler) (#674271)
  • Support defining GType properties from Python (Martin Pitt) (#674351)
  • Handle GType properties correctly (Bastian Winkler) (#674351)
  • Add missing GObject.TYPE_GTYPE (Martin Pitt)
  • Fix test_mainloop.py for Python 3 (Martin Pitt)
  • Make callback exception propagation test stricter (Martin Pitt) (#616279)
  • Add context management to freeze_notify() and handler_block(). (Simon Feltman) (#672324)
  • Add support for GFlags properties (Martin Pitt) (#620943)
  • Wrap GLib.Source.is_destroyed() method (Martin Pitt) (#524719)
  • Fix error message when trying to override a non-GI class (Martin Pitt) (#646667)
  • Fix segfault when accessing __grefcount__ before creating the GObject (Steve Frécinaux) (#640434)
  • Do not bind gobject_get_data() and gobject_set_data() (Steve Frécinaux) (#641944)
  • Add test case for multiple GLib.MainLoop instances (Martin Pitt) (#663068)
  • Add a ccallback type which is used to invoke callbacks passed to a vfunc (John (J5) Palmieri) (#644926)
  • Regression test: marshalling GValues in GHashTable (Alberto Mardegan) (#668903)
  • Update .gitignore (Martin Pitt)
  • Fix “distcheck” and tests with out-of-tree builds (Martin Pitt)
  • Add a pep8 check to the makefile (Johan Dahlin) (#672627)
  • PEP8 whitespace fixes (Johan Dahlin) (#672627)
  • PEP8: Remove trailing ; (Johan Dahlin) (#672627)
  • tests: Replace deprecated Python API (Martin Pitt)
  • Fail tests if they use or encounter deprecations (Martin Pitt)
  • Do not run tests in two phases any more (Martin Pitt)
  • test_overrides: Find local gsettings schema with current glib (Martin Pitt)
  • Add GtkComboBoxEntry compatibility (Paolo Borelli) (#672589)
  • Correct review comments from Martin (Johan Dahlin) (#672578)
  • Correct pyflakes warnings/errors (Johan Dahlin) (#672578)
  • Make tests fail on CRITICAL logs, too, and apply to all tests (Martin Pitt)
  • Support marshalling GI_TYPE_TAG_INTERFACE (Alberto Mardegan) (#668903)
  • Fix warnings on None values in added tree/list store rows (Martin Pitt) (#672463)
  • pygtkcompat test: Properly clean up PixbufLoader (Martin Pitt)

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