Random stuff

bzr commit –author

One of the features I recently discovered in Bazaar is the --author option for “bzr commit“.  This lets you make commits to a Bazaar branch on behalf of another person.  When used, the new revision credits two people: you as the committer and the other person as the author.

While Bazaar does make it easy for non-core contributors to send changes in a form that correctly attributes them (e.g. by publishing a branch or sending a bundle), I doubt we’ll ever see the end of pure patches.  Some cases include:

  • Patches based on a tarball release.   In these cases the contributor likely hasn’t even used the VCS.
  • People send simple diffs from e.g. “bzr diff” since that is sometimes the easiest solution (or what they do by default due to having transferred their knowledge from another VCS).
  • Some people use a VCS bridge so they can work with their favourite VCS.  They might not be able to provide their changes as Bazaar commits due to this.

The --author option lets you commit these changes in a way that credits the contributor for their work.  The author of the change will then be displayed in “bzr annotate” output and credited along with the you in the “bzr log” output.

The feature is also used by a number of plugins such as bzr-rebase: if you replay or rebase someone else’s changes, the new revisions will creit you as the committer and the original committer as the author.

SSL caching on Firefox 3

Since upgrading to Ubuntu Hardy, I’ve been enjoying using Firefox 3.  The reduced memory usage has made a lot of other things nicer to use (I don’t feel like I need to buy more memory now).  One thing that is nice to see fixed is caching of SSL content.

In previous versions of Firefox, SSL content was never cached to disk with the default settings.  While you certainly don’t want all SSL content to be written to disk, a lot of it can be cached without problem.  For example, it is important that the CSS and JavaScript for a page be served via SSL to avoid man in the middle attacks (injecting arbitrary active content into a secure page is bad), but there isn’t much harm in caching them to disk: if the attacker can modify the disk cache then SSL probably doesn’t matter much.

Now it was possible to turn on disk caching in Firefox 2 through the browser.cache.disk_cache_ssl hidden option, but it had a serious drawback: the security information for resources was not saved in the disk cache so you’d get a broken padlock if resources were loaded from the cache.

Firefox 3 fixes up the disk cache to record the security information though, so turning on disk_cache_ssl setting no longer results in a broken padlock.  But what about all the people using Firefox with its default settings (or those who do not want all SSL content cached to disk)?  For these users, the web server can still cause some content to be cached.

By sending the “Cache-Control: public” response header, the server can say that a resource can be stored in the disk cache.  Firefox 3 will respect this irrespective of the disk_cache_ssl setting.  This should bring Firefox back into parity with Internet Explorer with respect to network  performance on SSL web sites.

Psycopg migrated to Bazaar

Last week we moved psycopg from Subversion to Bazaar.  I did the migration using Gustavo Niemeyer‘s svn2bzr tool with a few tweaks to map the old Subversion committer IDs to the email address form conventionally used by Bazaar.

The tool does a good job of following tree copies and create related Bazaar branches.  It doesn’t have any special handling for stuff in the tags/ directory (it produces new branches, as it does for other tree copies).  To get real Bazaar tags, I wrote a simple post-processing script to calculate the heads of all the branches in a tags/ directory and set them as tags in another branch (provided those revisions occur in its ancestry).  This worked pretty well except for a few revisions synthesised by a previous cvs2svn migration.  As these tags were from pretty old psycopg 1 releases I don’t know how much it matters.

As there is no code browsing set up on initd.org yet, I set up mirrors of the 2.0.x and 1.x branches on Launchpad to do this:

It is pretty cool having access to the entire revision history locally, and should make it easier to maintain full credit for contributions from non-core developers.

Psycopg2 2.0.7 Released

Yesterday Federico released version 2.0.7 of psycopg2 (a Python database adapter for PostgreSQL).  I made a fair number of the changes in this release to make it more usable for some of Canonical‘s applications.  The new release should work with the development version of Storm, and shouldn’t be too difficult to get everything working with other frameworks.

Some of the improvements include:

  • Better selection of exceptions based on the SQLSTATE result field.  This causes a number of errors that were reported as ProgrammingError to use a more appropriate exception (e.g. DataError, OperationalError, InternalError).  This was the change that broke Storm’s test suite as it was checking for ProgrammingError on some queries that were clearly not programming errors.
  • Proper error reporting for commit() and rollback(). These methods now use the same error reporting code paths as execute(), so an integrity error on commit() will now raise IntegrityError rather than OperationalError.
  • The compile-time switch that controls whether the display_size member of Cursor.description is calculated is now turned off by default.  The code was quite expensive and the field is of limited use (and not provided by a number of other database adapters).
  • New QueryCanceledError and TransactionRollbackError exceptions.  The first is useful for handling queries that are canceled by statement_timeout.  The second provides a convenient way to catch serialisation failures and deadlocks: errors that indicate the transaction should be retried.
  • Fixes for a few memory leaks and GIL misuses. One of the leaks was in the notice processing code that could be particularly problematic for long-running daemon processes.
  • Better test coverage and a driver script to run the entire test suite in one go.  The tests should all pass too, provided your database cluster uses unicode (there was a report just before the release of one test failing for a LATIN1 cluster).

If you’re using previous versions of psycopg2, I’d highly recommend upgrading to this release.

Future work will probably involve support for the DB-API two phase commit extension, but I don’t know when I’ll have time to get to that.

Honey Bock Results

Since bottling the honey bock last month, I’ve tried a bottle last week and this week. While it is a very nice beer, the honey flavour is not very noticeable. That said, the second bottle I tried had a slightly stronger honey flavour than the first so it might just need to mature for another month or so.

If I was to do this beer again, it would make sense to use a stronger flavoured honey or just use more honey. Then again, perhaps it isn’t worth trying honey flavoured dark beers.

One beer I’d like to make again is Chilli Beer.  I haven’t seen any commercial equivalent to it, and it was great on a hot summer afternoon.  Since there were chilli pieces in the bottles of the last batch, it got hotter as it matured.  It is an interesting experience where taking a sip of the beer cools your moth down, but it starts heating up again once you swallow.