bazeldnf

Bazel library which allows dealing with the whole RPM dependency lifecycle solely with pure go rules and a static go binary.

Bazel rules

rpm rule

The rpm rule represents a pure RPM dependency. This dependency is not processed in any way. They can be added to your WORKSPACE file like this:

load("@bazeldnf//:deps.bzl", "rpm")

rpm(
    name = "libvirt-devel-6.1.0-2.fc32.x86_64.rpm",
    sha256 = "2ebb715341b57a74759aff415e0ff53df528c49abaa7ba5b794b4047461fa8d6",
    urls = [
        "https://download-ib01.fedoraproject.org/pub/fedora/linux/releases/32/Everything/x86_64/os/Packages/l/libvirt-devel-6.1.0-2.fc32.x86_64.rpm",
        "https://storage.googleapis.com/builddeps/2ebb715341b57a74759aff415e0ff53df528c49abaa7ba5b794b4047461fa8d6",
    ],
)

rpmtree

rpmtree Takes a list of rpm dependencies and merges them into a single tar package. rpmtree rules can be added like this to your BUILD files:

load("@bazeldnf//:deps.bzl", "rpmtree")

rpmtree(
    name = "rpmarchive",
    rpms = [
        "@libvirt-libs-6.1.0-2.fc32.x86_64.rpm//rpm",
        "@libvirt-devel-6.1.0-2.fc32.x86_64.rpm//rpm",
    ],
)

Since rpmarchive is just a tar archive, it can be put into a container immediately:

container_layer(
    name = "gcloud-layer",
    tars = [
        ":rpmarchive",
    ],
)

rpmtrees allow injecting relative symlinks (pkg_tar can only inject absolute symlinks) and xattrs capabilities. The following example adds a relative link and gives one binary the cap_net_bind_service capability to connect to privileged ports:

rpmtree(
    name = "rpmarchive",
    rpms = [
        "@libvirt-libs-6.1.0-2.fc32.x86_64.rpm//rpm",
        "@libvirt-devel-6.1.0-2.fc32.x86_64.rpm//rpm",
    ],
    symlinks = {
        "/var/run": "../run",
    },
    capabilities = {
        "/usr/libexec/qemu-kvm": [
            "cap_net_bind_service",
        ],
    },
)

Running bazeldnf with bazel

The bazeldnf repository needs to be added to your WORKSPACE:

load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")

http_archive(
    name = "bazeldnf",
    sha256 = "74f977ab8f13e466168ff0c80322bcb665db9f79d1bc497c742f9512737b91ea",
    strip_prefix = "bazeldnf-0.0.1",
    urls = [
        "https://github.com/rmohr/bazeldnf/archive/v0.0.1.tar.gz",
    ],
)

load("@io_bazel_rules_go//go:deps.bzl", "go_register_toolchains", "go_rules_dependencies")
load("@bazeldnf//:deps.bzl", "bazeldnf_dependencies")

go_rules_dependencies()

go_register_toolchains()

bazeldnf_dependencies()

Define the bazeldnf executable rule in your BUILD.bazel file:

load("@bazeldnf//:def.bzl", "bazeldnf")

bazeldnf(name = "bazeldnf")

After adding this code, you can run bazeldnf with Bazel:

bazel run //:bazeldnf -- --help

Libraries and Headers

One important use-case is to expose headers and libraries inside the RPMs to build targets in bazel. If we would just blindly expose all libraries to build targets, bazel would try to link any one of them to our binary. This would obviously not work. Therefore we need a mediator between cc_library and rpmtree. This mediator is the tar2files target. This target allows extracting a subset of libraries and headers and providing them to cc_library targets.

An example:

load("@bazeldnf//:deps.bzl", "rpm", "rpmtree", "tar2files")

tar2files(
    name = "libvirt-libs",
    files = {
        "/usr/include/libvirt": [
            "libvirt-admin.h",
            "libvirt-common.h",
            "libvirt-domain-checkpoint.h",
            "libvirt-domain-snapshot.h",
            "libvirt-domain.h",
            "libvirt-event.h",
        ],
        "/usr/lib64": [
            "libacl.so.1",
            "libacl.so.1.1.2253",
            "libattr.so.1",
        ],
    },
    tar = ":libvirt-devel",
    visibility = ["//visibility:public"],
)

tar can take any input which is a tar archive. Conveniently this is what rpmtree creates as the default target. So any rpmtree can be used here. The files section contains then files per folder which one wants to expose to cc_library:

cc_library(
    name = "rpmlibs",
    srcs = [
        ":libvirt-libs/usr/lib64",
    ],
    hdrs = [
        ":libvirt-libs/usr/include/libvirt",
    ],
    strip_include_prefix="/libvirt-libs/",
    prefix= "libvirt",
)

At this point source code linking to these libraries can be compiled, but unit tests would only work if we would manually list any transitive library. This would be tedious and error prone. However bazeldnf can introspect for you shared libraries and create tar2files rules for you, based on a provided set of libraries.

First define a target like this:

load("@bazeldnf//:deps.bzl", "rpm", "rpmtree", "tar2files")
load("@bazeldnf//:def.bzl", "bazeldnf")

bazeldnf(
    name = "ldd",
    command = "ldd",
    libs = [
        "/usr/lib64/libvirt-lxc.so.0",
        "/usr/lib64/libvirt-qemu.so.0",
        "/usr/lib64/libvirt.so.0",
    ],
    rpmtree = ":libvirt-devel",
    rulename = "libvirt-libs",
)

rulename containes the tar2files target name, rpmtree references a given rpmtree and libs contains libraries which one wants to link. When now executing the target like this:

bazel run //:ldd

the tar2files target will be updated with all transitive library dependencies for the specified libraries. In addition, all header directories are updated too for convenience.

Dependency resolution

One key part of managing RPM dependencies and RPM repository updates via bazel is the ability to resolve RPM dependencies from repos without external tools like dnf or yum and write the resolved dependencies to your WORKSPACE.

Here an example on how to add libvirt and bash to your WORKSPACE and BUILD files.

First write the repo.yaml file which contains some basic rpm repos to query:

bazeldnf init --fc 32 # write a repo.yaml file containing the usual release and update repos for fc32

Then write a rpmtree rule called libvirttree to your BUILD file and all corresponding RPM dependencies into your WORKSPACE for libvirt:

bazeldnf rpmtree --workspace /my/WORKSPACE --buildfile /my/BUILD.bazel --name libvirttree libvirt

Do the same for bash with a bashrpmtree target:

bazeldnf rpmtree --workspace /my/WORKSPACE --buildfile /my/BUILD.bazel --name bashtree bash

Finally prune all unreferenced old RPM files:

bazeldnf prune --workspace /my/WORKSPACE --buildfile /my/BUILD.bazel

By default bazeldnf rpmtree will try to find a solution which only contains the newest packages of all involved repositories. The only exception are pinned versions themselves. If pinned version require other outdated packages, the --nobest option can be supplied. With this option all packages are considered. Newest packages will have the higest weight but it may not always be able to choose them and older packages may be pulled in instead.

Dependency resolution limitations

Missing features

Resolving requires entries which contain boolean logic like (gcc if something)

Deliberately not supported

The goal is to build minimal containers with RPMs based on scratch containers. Therefore the following RPM repository hints will be ignored:

recommends
supplements
suggests
enhances

leoluk/bazeldnf