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[Martin Pool <mbp@xxxxxxxxxxxxx>]

(Launchpad bounced my mail during the upgrade today)


---------- Forwarded message ----------
From: Martin Pool <mbp@xxxxxxxxxxxxx>
Date: 2009/9/24
Subject: which version of bzr for launchpad?
To: Launchpad Community Development Team
<launchpad-dev@xxxxxxxxxxxxxxxxxxx>, Robert Collins
<robertc@xxxxxxxxxxxxxxxxx>, John Arbash Meinel
<john@xxxxxxxxxxxxxxxxx>, Ian Clatworthy
<ian.clatworthy@xxxxxxxxxxxxx>, Vincent Ladeuil
<v.ladeuil+lp@xxxxxxx>, Andrew Bennetts
<andrew.bennetts@xxxxxxxxxxxxx>


I had a talk to jml and thumper about this recently, and thought I
would send a note here for the larger audience.

Bazaar now maintains two branches, a stable/bugfix-only 2.0 branch,
and an ongoing development branch 2.1dev.  (See
<http://doc.bazaar-vcs.org/developers/cycle.html>).  As much as we
can, we will make no changes to 2.0 that will break api compatibility,
or any other kind.  They will be able to interoperate on both the
network and formats.   The development branch may introduce new data
formats, though we don't immediately anticipate doing this.  It likely
will add new smartserver verbs, but it will have a fallback for older
servers.  2.1 will still be tested and get the same degree of care we
always have, but we'll be a bit more free to remove deprecated or
non-user-affecting compatibility code.  So the only difference is the
rate of change, not the degree of quality.

The question then arises which version Launchpad should run for
codehosting, and the answer is that it will run the development
branch, 2.1b1 etc.  People using old clients should be fine, and
people using new features or formats introduced in the development
branch will be able to use them against Launchpad.  As we change APIs,
Launchpad may need to update their own code, but they do this anyhow
as part of their monthly integrations and it is not onerous.

Launchpad will at some point in the future add an edge codehost, which
will run Launchpad's own tip, then be merged to the lpnet (ie stable)
servers in monthly releases.  edge will run only slightly ahead with
the bzr version, for example being on 2.1b2 when lpnet is on 2.1b1.
This gives some opportunity for testing.

The biggest risk seems to be that a change in 2.1.x may introduce
bugs, either to do with operation with old clients or otherwise.  The
best way to address this is (aside from general quality development)
to test each release as it's integrated on the staging and edge
codehost.  At least this way we will find any such issues earlier in
bzr's cycle rather than at the 2.1rc1 point.

It may be interesting in the future to allow the client to specify the
remote bzr commandname as eg 'bzr-2.0' and then we could have several
available servers on the Launchpad side; this would require including
multiple bzr trees in the deployment.

--
Martin <http://launchpad.net/~mbp/>



-- 
Martin <http://launchpad.net/~mbp/>