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- Committer: Launchpad Patch Queue Manager
- Date: 2012-01-06 18:11:49 UTC
- mfrom: (14646.1.1 bug578854)
- Revision ID: launchpad@pqm.canonical.com-20120106181149-jr3427anqojecnjh
[r=sinzui][bug=578854] Update buildout docs for clarity
- files modified:
- doc/buildout.txt
added
removed
doc/buildout.txt
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Launchpad Buildout
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******************
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Launchpad is moving to using the buildout_ (or "zc.buildout") build system. It
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will gradually replace the sourcecode directory, and hopefully also the
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Launchpad Makefile.
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Launchpad uses the buildout_ (or "zc.buildout") build system.
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Buildout's biggest strength is managing Python packages. That is also
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our focus for it.
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Buildout's biggest strength is managing Python packages. That will also be our
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primary focus for it. Meanwhile, apt will continue to manage our Python
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language installation, as well some or all of our non-Python dependencies, such
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as PostgreSQL. While Bazaar will continue to be an essential part of our
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toolchain, we will move away from using it to incorporate source code trees of
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our dependencies.
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We have at least two other ways of managing dependencies. Apt
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manages our Python language installation, as well as many of our
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non-Python system-level dependencies, such as PostgreSQL. The
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sourcecode directory is our other way of managing dependencies. It is
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supposed to only contain dependencies that are not standard Python
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packages. bzr plugins and Javascript libraries are existing examples.
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If you are not interested in our `Motivations`_ or in an `Introduction to
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zc.buildout`_, all developers will at least want to read the very brief
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* We want more careful specification of our dependencies across branches.
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[INTERNAL] [EXTERNAL]
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This is a real concern pertinent both for our "trunks" (devel, stable,
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db-devel, db-stable) and for our development boxes. For instance, now, in our
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trunks, when we want to update a dependency, we need to make sure that *all*
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the current Launchpad trunks work with the dependency initially; then submit
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a new Launchpad branch that uses the change dependency. A mistake can
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even potentially break one or both of the db-* trunks, since PQM only tests
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against one branch (usually devel), and sourcecode changes affect all
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branches at once. For simplicity, speed, and safety, we want to be able to
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submit a single branch that incorporates the source dependencies and the
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associated changes at once.
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This is a real concern pertinent both for our "trunks" (devel,
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stable, db-devel, db-stable) and for our development boxes. For
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instance, before incorporating buildout, in our trunks, when we want
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to update a dependency, we needed to make sure that *all* the
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current Launchpad trunks work with the dependency initially; then
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submit a new Launchpad branch that uses the change dependency. A
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mistake can even potentially break one or both of the db-* trunks,
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since PQM only tests against one branch (usually devel), and
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sourcecode changes affect all branches at once. For simplicity,
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speed, and safety, we want to be able to submit a single branch that
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incorporates the source dependencies and the associated changes at
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once.
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This is also true, if less critical and easier to work around, on developer
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boxes. Without care, changes to sourcecode when working on dependencies will
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A significant number of projects do not always have a pristine trunk, and
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many also spend extra effort on polish, bug fixes, and compatibility before a
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release. If we do not desperately need a new feature on trunk, using a
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release is generally regarded as a safer, better practice. Our current usage
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release is generally regarded as a safer, better practice. Our earlier usage
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of bzr branches of the development trunks does not encourage this practice.
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* We want to be encouraged to make the effort to interact with upstream
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projects to have our patches integrated. [EXTERNAL]
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Interacting and negotiating with upstream is undeniably more time-consuming
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than our current practice of maintaining local bzr branches with our patches,
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especially short-term. But our current practice is not good open-source
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community behavior--an ironic characteristic for a project like Launchpad. It
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also can cause problems down the road, for instance, if the patch becomes
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Interacting and negotiating with upstream is undeniably more
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time-consuming than our previous practice of maintaining local bzr
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branches with our patches, especially short-term. But our previous
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use of bzr branches is not good open-source community behavior--an
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ironic characteristic for a project like Launchpad. It also can
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cause problems down the road, for instance, if the patch becomes
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stale and we want to migrate to new releases.
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* We want to be protected from changes and differences in our operating system.
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This is a concern both over time and across different Launchpad environments.
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First, our operating system, Ubuntu, is driven by many needs and goals.
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Launchpad is among them, but generally Launchpad serves Ubuntu, not the
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reverse. For instance, recently Jaunty dropped Launchpad's Python version.
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The Ubuntu developers had good reason--Python 2.4 has not been supported by
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the Python developers for some time--but it caused a significant
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inconvenience to the Launchpad team. Managing our dependencies, particularly
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the Python library dependencies, can help alleviate these problems.
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First, our operating system, Ubuntu, is driven by many needs and
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goals. Launchpad is among them, but generally Launchpad serves
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Ubuntu, not the reverse. For instance, Jaunty dropped Launchpad's
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Python version. The Ubuntu developers had good reason--Python 2.4
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has not been supported by the Python developers for some time--but
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it caused a significant inconvenience to the Launchpad
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team. Managing our dependencies, particularly the Python library
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dependencies, can help alleviate these problems.
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Second, Launchpad developers run a significantly different version of the
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operating system than that run in production. Maintaining our Python library
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./bin/buildout -v buildout:install-from-cache=false | tee out.txt | grep 'Picked'
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The first part (``./bin/buildout -v buildout:install-from-cache=false``)
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will run buildout, allowing it to download source packages from the
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Internet to ``download-cache/dist``. The second part (``tee out.txt``) will
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dump the full output to the ``out.txt`` file in case you need to debug a
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problem. The last part (``grep 'Picked'``) will filter the output so that
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only additional packages--dependencies of your dependency--will be listed.
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Look at the output. You need to see if it means that you have dependencies,
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some of which may be indirect dependencies. Here's an imaginary example
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output::
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The first part (``./bin/buildout -v
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buildout:install-from-cache=false``) will run buildout, allowing
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it to download source packages from the Internet to
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``download-cache/dist``. The second part (``tee out.txt``) will
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dump the full output to the ``out.txt`` file in case you need to
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debug a problem. The last part (``grep 'Picked'``) will filter the
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output so that only additional packages--dependencies of your
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dependency--will be listed. You need to see if it means that you
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have dependencies, some of which may be indirect
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dependencies. We'll see how to do this with an example. Here's an
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imaginary output::
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Picked: ipython = 0.9.1
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Picked: lazr.foom = 1.4
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Picked: zope.bar = 3.6.1
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Picked: z3c.shazam = 2.0.1
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At this time, note that the output will include at least one, and possibly
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more, spurious "Picked:" listings. ipython, in particular, shows up
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repeatedly.
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In our example, other than the spurious ``ipython`` listing, this means
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that these packages have also been added to your ``download-cache/dist``
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directory. You also need to add those versions to the ``versions.cfg``
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file::
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In our example, this means that these packages have been added to
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your ``download-cache/dist`` directory. You now need to add those
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versions to the ``versions.cfg`` file::
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ipython = 0.9.1
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lazr.foom = 1.4
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zope.bar = 3.6.1
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z3c.shazam = 2.0.1
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Note that the output might include at least one, and possibly
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more, spurious "Picked:" listings. ipython, in particular, has
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shown up in the past incorrectly--that is, when you try to add the
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file to the download-cache/dist directory, you'll discover that it
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is already there; and you'll see that versions.cfg already
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specifies the version. As long as the test passes (see step 5,
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below), you can ignore this.
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5. Test.
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[TODO] Note that you can tell ec2test to include all uncommitted
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distributions from the local download-cache in its tests. If you do this,
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you cannot use the ec2test feature to submit on test success. Also, if you
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have uncommitted distributions and you do *not* explicitly tell ec2test to
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include or ignore the uncommitted distributions, it will refuse to start
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an instance.
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6. Check old versions in the download-cache. If you are sure that they are
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not in use any more, *anywhere*, then remove them to save checkout space.
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More explicitly, check with the LOSAs to see if they are in use in
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production and send an email to launchpad-dev@lists.launchpad.net before
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deleting anything if you are unsure.
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7. Commit the changes (``cd download-cache``, ``bzr up``,
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``bzr commit -m 'Add lazr.foom 1.1.2 and depdendencies to the download
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cache'``) to the shared download cache when you are sure it is what you
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want.
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*Never* modify a package in the download-cache.
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Note that you can tell ``ec2 test`` to include all uncommitted
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distributions from the local download-cache in its tests with the
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``--include-download-cache-changes`` flag (or ``-c``). If you do
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this, you cannot use the ec2 test feature to submit on test
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success. Also, if you have uncommitted distributions and you do
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*not* explicitly tell ec2 test to include or ignore the
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uncommitted distributions, it will refuse to start an instance.
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6. Check old versions in the download-cache. If you are sure that
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they are not in use any more, *anywhere*, then remove them to save
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checkout space. More explicitly, check with the LOSAs to see if
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they are in use in production and send an email to
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launchpad-dev@lists.launchpad.net before deleting anything if you
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are unsure. A rule of thumb is that it's worth starting this
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investigation if the replacement has already been in use by the
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Launchpad tree for more than a month. You can approximate this
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information by using ``bzr log`` on the newer (replacement)
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download-cache/dist file for the particular package.
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7. Now you need to share your package changes with the rest of the
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team. You must do this before submitting your Launchpad branch to
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PQM or else your branch will not build properly anywhere else,
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including buildbot. Commit the changes (``cd download-cache``,
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bzr add the needed files, ``bzr up``, ``bzr commit -m 'Add
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lazr.foom 1.1.2 and depdendencies to the download cache'``) to the
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shared download cache when you are sure it is what you want.
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*Never* modify a package in the download-cache. A change in code must mean a
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change in version number, or else very bad inconsistencies and
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confusion across build environments will happen.
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