.. SPDX-License-Identifier: CC-BY-SA-2.0-UK

Maintaining Build Output Quality with ``buildhistory``
******************************************************

Many factors can influence the quality of a build. For example, if you
upgrade a recipe to use a new version of an upstream software package or
you experiment with some new configuration options, subtle changes can
occur that you might not detect until later. Consider the case where
your recipe is using a newer version of an upstream package. In this
case, a new version of a piece of software might introduce an optional
dependency on another library, which is auto-detected. If that library
has already been built when the software is building, the software will
link to the built library and that library will be pulled into your
image along with the new software even if you did not want the library.

The :ref:`ref-classes-buildhistory` class helps you maintain the quality of
your build output. You can use the class to highlight unexpected and possibly
unwanted changes in the build output. When you enable build history, it records
information about the contents of each package and image and then commits that
information to a local Git repository where you can examine the information.

The remainder of this section describes the following:

-  :ref:`How you can enable and disable build history <dev-manual/build-quality:enabling and disabling build history>`

-  :ref:`How to understand what the build history contains <dev-manual/build-quality:understanding what the build history contains>`

-  :ref:`How to limit the information used for build history <dev-manual/build-quality:using build history to gather image information only>`

-  :ref:`How to examine the build history from both a command-line and web interface <dev-manual/build-quality:examining build history information>`

Enabling and Disabling Build History
====================================

Build history is disabled by default. To enable it, add the following
:term:`INHERIT` statement and set the :term:`BUILDHISTORY_COMMIT` variable to
"1" at the end of your ``conf/local.conf`` file found in the
:term:`Build Directory`::

   INHERIT += "buildhistory"
   BUILDHISTORY_COMMIT = "1"

Enabling build history as
previously described causes the OpenEmbedded build system to collect
build output information and commit it as a single commit to a local
:ref:`overview-manual/development-environment:git` repository.

.. note::

   Enabling build history increases your build times slightly,
   particularly for images, and increases the amount of disk space used
   during the build.

You can disable build history by removing the previous statements from
your ``conf/local.conf`` file.

Understanding What the Build History Contains
=============================================

Build history information is kept in ``${``\ :term:`TOPDIR`\ ``}/buildhistory``
in the :term:`Build Directory` as defined by the :term:`BUILDHISTORY_DIR`
variable. Here is an example abbreviated listing:

.. image:: figures/buildhistory.png
   :align: center
   :width: 50%

At the top level, there is a ``metadata-revs`` file that lists the
revisions of the repositories for the enabled layers when the build was
produced. The rest of the data splits into separate ``packages``,
``images`` and ``sdk`` directories, the contents of which are described
as follows.

Build History Package Information
---------------------------------

The history for each package contains a text file that has name-value
pairs with information about the package. For example,
``buildhistory/packages/i586-poky-linux/busybox/busybox/latest``
contains the following:

.. code-block:: none

   PV = 1.22.1
   PR = r32
   RPROVIDES =
   RDEPENDS = glibc (>= 2.20) update-alternatives-opkg
   RRECOMMENDS = busybox-syslog busybox-udhcpc update-rc.d
   PKGSIZE = 540168
   FILES = /usr/bin/* /usr/sbin/* /usr/lib/busybox/* /usr/lib/lib*.so.* \
      /etc /com /var /bin/* /sbin/* /lib/*.so.* /lib/udev/rules.d \
      /usr/lib/udev/rules.d /usr/share/busybox /usr/lib/busybox/* \
      /usr/share/pixmaps /usr/share/applications /usr/share/idl \
      /usr/share/omf /usr/share/sounds /usr/lib/bonobo/servers
   FILELIST = /bin/busybox /bin/busybox.nosuid /bin/busybox.suid /bin/sh \
      /etc/busybox.links.nosuid /etc/busybox.links.suid

Most of these
name-value pairs correspond to variables used to produce the package.
The exceptions are ``FILELIST``, which is the actual list of files in
the package, and ``PKGSIZE``, which is the total size of files in the
package in bytes.

There is also a file that corresponds to the recipe from which the package
came (e.g. ``buildhistory/packages/i586-poky-linux/busybox/latest``):

.. code-block:: none

   PV = 1.22.1
   PR = r32
   DEPENDS = initscripts kern-tools-native update-rc.d-native \
      virtual/i586-poky-linux-compilerlibs virtual/i586-poky-linux-gcc \
      virtual/libc virtual/update-alternatives
   PACKAGES = busybox-ptest busybox-httpd busybox-udhcpd busybox-udhcpc \
      busybox-syslog busybox-mdev busybox-hwclock busybox-dbg \
      busybox-staticdev busybox-dev busybox-doc busybox-locale busybox

Finally, for those recipes fetched from a version control system (e.g.,
Git), there is a file that lists source revisions that are specified in
the recipe and the actual revisions used during the build. Listed
and actual revisions might differ when
:term:`SRCREV` is set to
${:term:`AUTOREV`}. Here is an
example assuming
``buildhistory/packages/qemux86-poky-linux/linux-yocto/latest_srcrev``)::

   # SRCREV_machine = "38cd560d5022ed2dbd1ab0dca9642e47c98a0aa1"
   SRCREV_machine = "38cd560d5022ed2dbd1ab0dca9642e47c98a0aa1"
   # SRCREV_meta = "a227f20eff056e511d504b2e490f3774ab260d6f"
   SRCREV_meta ="a227f20eff056e511d504b2e490f3774ab260d6f"

You can use the
``buildhistory-collect-srcrevs`` command with the ``-a`` option to
collect the stored :term:`SRCREV` values from build history and report them
in a format suitable for use in global configuration (e.g.,
``local.conf`` or a distro include file) to override floating
:term:`AUTOREV` values to a fixed set of revisions. Here is some example
output from this command::

   $ buildhistory-collect-srcrevs -a
   # all-poky-linux
   SRCREV:pn-ca-certificates = "07de54fdcc5806bde549e1edf60738c6bccf50e8"
   SRCREV:pn-update-rc.d = "8636cf478d426b568c1be11dbd9346f67e03adac"
   # core2-64-poky-linux
   SRCREV:pn-binutils = "87d4632d36323091e731eb07b8aa65f90293da66"
   SRCREV:pn-btrfs-tools = "8ad326b2f28c044cb6ed9016d7c3285e23b673c8"
   SRCREV_bzip2-tests:pn-bzip2 = "f9061c030a25de5b6829e1abf373057309c734c0"
   SRCREV:pn-e2fsprogs = "02540dedd3ddc52c6ae8aaa8a95ce75c3f8be1c0"
   SRCREV:pn-file = "504206e53a89fd6eed71aeaf878aa3512418eab1"
   SRCREV_glibc:pn-glibc = "24962427071fa532c3c48c918e9d64d719cc8a6c"
   SRCREV:pn-gnome-desktop-testing = "e346cd4ed2e2102c9b195b614f3c642d23f5f6e7"
   SRCREV:pn-init-system-helpers = "dbd9197569c0935029acd5c9b02b84c68fd937ee"
   SRCREV:pn-kmod = "b6ecfc916a17eab8f93be5b09f4e4f845aabd3d1"
   SRCREV:pn-libnsl2 = "82245c0c58add79a8e34ab0917358217a70e5100"
   SRCREV:pn-libseccomp = "57357d2741a3b3d3e8425889a6b79a130e0fa2f3"
   SRCREV:pn-libxcrypt = "50cf2b6dd4fdf04309445f2eec8de7051d953abf"
   SRCREV:pn-ncurses = "51d0fd9cc3edb975f04224f29f777f8f448e8ced"
   SRCREV:pn-procps = "19a508ea121c0c4ac6d0224575a036de745eaaf8"
   SRCREV:pn-psmisc = "5fab6b7ab385080f1db725d6803136ec1841a15f"
   SRCREV:pn-ptest-runner = "bcb82804daa8f725b6add259dcef2067e61a75aa"
   SRCREV:pn-shared-mime-info = "18e558fa1c8b90b86757ade09a4ba4d6a6cf8f70"
   SRCREV:pn-zstd = "e47e674cd09583ff0503f0f6defd6d23d8b718d3"
   # qemux86_64-poky-linux
   SRCREV_machine:pn-linux-yocto = "20301aeb1a64164b72bc72af58802b315e025c9c"
   SRCREV_meta:pn-linux-yocto = "2d38a472b21ae343707c8bd64ac68a9eaca066a0"
   # x86_64-linux
   SRCREV:pn-binutils-cross-x86_64 = "87d4632d36323091e731eb07b8aa65f90293da66"
   SRCREV_glibc:pn-cross-localedef-native = "24962427071fa532c3c48c918e9d64d719cc8a6c"
   SRCREV_localedef:pn-cross-localedef-native = "794da69788cbf9bf57b59a852f9f11307663fa87"
   SRCREV:pn-debianutils-native = "de14223e5bffe15e374a441302c528ffc1cbed57"
   SRCREV:pn-libmodulemd-native = "ee80309bc766d781a144e6879419b29f444d94eb"
   SRCREV:pn-virglrenderer-native = "363915595e05fb252e70d6514be2f0c0b5ca312b"
   SRCREV:pn-zstd-native = "e47e674cd09583ff0503f0f6defd6d23d8b718d3"

.. note::

   Here are some notes on using the ``buildhistory-collect-srcrevs`` command:

   -  By default, only values where the :term:`SRCREV` was not hardcoded
      (usually when :term:`AUTOREV` is used) are reported. Use the ``-a``
      option to see all :term:`SRCREV` values.

   -  The output statements might not have any effect if overrides are
      applied elsewhere in the build system configuration. Use the
      ``-f`` option to add the ``forcevariable`` override to each output
      line if you need to work around this restriction.

   -  The script does apply special handling when building for multiple
      machines. However, the script does place a comment before each set
      of values that specifies which triplet to which they belong as
      previously shown (e.g., ``i586-poky-linux``).

Build History Image Information
-------------------------------

The files produced for each image are as follows:

-  ``image-files:`` A directory containing selected files from the root
   filesystem. The files are defined by
   :term:`BUILDHISTORY_IMAGE_FILES`.

-  ``build-id.txt:`` Human-readable information about the build
   configuration and metadata source revisions. This file contains the
   full build header as printed by BitBake.

-  ``*.dot:`` Dependency graphs for the image that are compatible with
   ``graphviz``.

-  ``files-in-image.txt:`` A list of files in the image with
   permissions, owner, group, size, and symlink information.

-  ``image-info.txt:`` A text file containing name-value pairs with
   information about the image. See the following listing example for
   more information.

-  ``installed-package-names.txt:`` A list of installed packages by name
   only.

-  ``installed-package-sizes.txt:`` A list of installed packages ordered
   by size.

-  ``installed-packages.txt:`` A list of installed packages with full
   package filenames.

.. note::

   Installed package information is able to be gathered and produced
   even if package management is disabled for the final image.

Here is an example of ``image-info.txt``:

.. code-block:: none

   DISTRO = poky
   DISTRO_VERSION = 3.4+snapshot-a0245d7be08f3d24ea1875e9f8872aa6bbff93be
   USER_CLASSES = buildstats
   IMAGE_CLASSES = qemuboot qemuboot license_image
   IMAGE_FEATURES = allow-empty-password empty-root-password allow-root-login post-install-logging
   IMAGE_LINGUAS =
   IMAGE_INSTALL = packagegroup-core-boot speex speexdsp
   BAD_RECOMMENDATIONS =
   NO_RECOMMENDATIONS =
   PACKAGE_EXCLUDE =
   ROOTFS_POSTPROCESS_COMMAND = ssh_allow_empty_password  ssh_allow_root_login  postinst_enable_logging  rootfs_update_timestamp   write_image_test_data   empty_var_volatile   sort_passwd rootfs_reproducible
   IMAGE_POSTPROCESS_COMMAND =  buildhistory_get_imageinfo
   IMAGESIZE = 9265

Other than ``IMAGESIZE``,
which is the total size of the files in the image in Kbytes, the
name-value pairs are variables that may have influenced the content of
the image. This information is often useful when you are trying to
determine why a change in the package or file listings has occurred.

Using Build History to Gather Image Information Only
----------------------------------------------------

As you can see, build history produces image information, including
dependency graphs, so you can see why something was pulled into the
image. If you are just interested in this information and not interested
in collecting specific package or SDK information, you can enable
writing only image information without any history by adding the
following to your ``conf/local.conf`` file found in the
:term:`Build Directory`::

   INHERIT += "buildhistory"
   BUILDHISTORY_COMMIT = "0"
   BUILDHISTORY_FEATURES = "image"

Here, you set the
:term:`BUILDHISTORY_FEATURES`
variable to use the image feature only.

Build History SDK Information
-----------------------------

Build history collects similar information on the contents of SDKs (e.g.
``bitbake -c populate_sdk imagename``) as compared to information it
collects for images. Furthermore, this information differs depending on
whether an extensible or standard SDK is being produced.

The following list shows the files produced for SDKs:

-  ``files-in-sdk.txt:`` A list of files in the SDK with permissions,
   owner, group, size, and symlink information. This list includes both
   the host and target parts of the SDK.

-  ``sdk-info.txt:`` A text file containing name-value pairs with
   information about the SDK. See the following listing example for more
   information.

-  ``sstate-task-sizes.txt:`` A text file containing name-value pairs
   with information about task group sizes (e.g. :ref:`ref-tasks-populate_sysroot`
   tasks have a total size). The ``sstate-task-sizes.txt`` file exists
   only when an extensible SDK is created.

-  ``sstate-package-sizes.txt:`` A text file containing name-value pairs
   with information for the shared-state packages and sizes in the SDK.
   The ``sstate-package-sizes.txt`` file exists only when an extensible
   SDK is created.

-  ``sdk-files:`` A folder that contains copies of the files mentioned
   in ``BUILDHISTORY_SDK_FILES`` if the files are present in the output.
   Additionally, the default value of ``BUILDHISTORY_SDK_FILES`` is
   specific to the extensible SDK although you can set it differently if
   you would like to pull in specific files from the standard SDK.

   The default files are ``conf/local.conf``, ``conf/bblayers.conf``,
   ``conf/auto.conf``, ``conf/locked-sigs.inc``, and
   ``conf/devtool.conf``. Thus, for an extensible SDK, these files get
   copied into the ``sdk-files`` directory.

-  The following information appears under each of the ``host`` and
   ``target`` directories for the portions of the SDK that run on the
   host and on the target, respectively:

   .. note::

      The following files for the most part are empty when producing an
      extensible SDK because this type of SDK is not constructed from
      packages as is the standard SDK.

   -  ``depends.dot:`` Dependency graph for the SDK that is compatible
      with ``graphviz``.

   -  ``installed-package-names.txt:`` A list of installed packages by
      name only.

   -  ``installed-package-sizes.txt:`` A list of installed packages
      ordered by size.

   -  ``installed-packages.txt:`` A list of installed packages with full
      package filenames.

Here is an example of ``sdk-info.txt``:

.. code-block:: none

   DISTRO = poky
   DISTRO_VERSION = 1.3+snapshot-20130327
   SDK_NAME = poky-glibc-i686-arm
   SDK_VERSION = 1.3+snapshot
   SDKMACHINE =
   SDKIMAGE_FEATURES = dev-pkgs dbg-pkgs
   BAD_RECOMMENDATIONS =
   SDKSIZE = 352712

Other than ``SDKSIZE``, which is
the total size of the files in the SDK in Kbytes, the name-value pairs
are variables that might have influenced the content of the SDK. This
information is often useful when you are trying to determine why a
change in the package or file listings has occurred.

Examining Build History Information
-----------------------------------

You can examine build history output from the command line or from a web
interface.

To see any changes that have occurred (assuming you have
:term:`BUILDHISTORY_COMMIT` = "1"),
you can simply use any Git command that allows you to view the history
of a repository. Here is one method::

   $ git log -p

You need to realize,
however, that this method does show changes that are not significant
(e.g. a package's size changing by a few bytes).

There is a command-line tool called ``buildhistory-diff``, though,
that queries the Git repository and prints just the differences that
might be significant in human-readable form. Here is an example::

   $ bitbake-builds/layers/openembedded-core/scripts/buildhistory-diff . HEAD^
   Changes to images/qemux86_64/glibc/core-image-minimal (files-in-image.txt):
      /etc/anotherpkg.conf was added
      /sbin/anotherpkg was added
      * (installed-package-names.txt):
      *   anotherpkg was added
   Changes to images/qemux86_64/glibc/core-image-minimal (installed-package-names.txt):
      anotherpkg was added
   packages/qemux86_64-poky-linux/v86d: PACKAGES: added "v86d-extras"
      * PR changed from "r0" to "r1"
      * PV changed from "0.1.10" to "0.1.12"
   packages/qemux86_64-poky-linux/v86d/v86d: PKGSIZE changed from 110579 to 144381 (+30%)
      * PR changed from "r0" to "r1"
      * PV changed from "0.1.10" to "0.1.12"

.. note::

   The ``buildhistory-diff`` tool requires the ``GitPython``
   package. Be sure to install it using Pip3 as follows::

         $ pip3 install GitPython --user


   Alternatively, you can install ``python3-git`` using the appropriate
   distribution package manager (e.g. ``apt``, ``dnf``, or ``zipper``).

To see changes to the build history using a web interface, follow the
instruction in the ``README`` file
:yocto_git:`here </buildhistory-web/>`.

Here is a sample screenshot of the interface:

.. image:: figures/buildhistory-web.png
   :width: 100%