The build process is controlled by the Makefile found in the root of the module. This builds various weave net executables, and also builds docker images. It uses a complex process for building multi-architecture docker images, involving cross-compilation, architecture-wise image naming, and the manifest tool. Here are some observations.
Several parts of the Makefile assume that the build machine's architecture is amd64.
The makefile can build things either on the host machine, or in a docker container. The Makefile parameter BUILD_IN_CONTAINER controls this. If chosen, the build container itself runs Docker in Docker, bind mounts the source directory, and builds using the same Makefile.
The build process requires CGO_ENABLED=1, and needs the presence of an architecture-specific C compiler. It also needs an architecture-specific libpcap.a to be available in the build machine. If building outside of a container, all this has to be provided ahead of time. If inside, the Makefile can build a build container image which contains all this, and then create a container from that image and run the rest of the build process in that container.
The build container image is built from the following directory:
- build/
The build container image is created from a Debian buster-based base image. It installs the libpcap-dev package for the build platform (assumed to be amd64). It then installs cross-compilers for other supported architectures(arm, arm64, ppc64le, s390x), downloads libpcap source code (version 1.6.2) and compiles it for each architecture. Details can be found in the build container image Dockerfile, at build/Dockerfile.
Either way, the build process builds the following executables:
- prog/weaver/weaver
- prog/sigproxy/sigproxy
- prog/kube-utils/kube-utils
- prog/weave-npc/weave-npc
- prog/weavewait/weavewait
- prog/weavewait/weavewait_noop
- prog/weavewait/weavewait_nomcast
- prog/weaveutil/weaveutil
- tools/runner/runner
- test/tls/tls
- test/images/network-tester/webserver
After building these, the build process builds a number of Docker images. To do this, it generates per-architecture Dockerfiles from the following "template" files:
- prog/weave-kube/Dockerfile.template
- prog/weave-npc/Dockerfile.template
- prog/weaveexec/Dockerfile.template
- prog/weaver/Dockerfile.template
The templates work as follows:
For prog/weaver/Dockerfile.template, the template fills in an Alpine base image. The image is controlled by the Makefile parameter ALPINE_BASEIMAGE. When building for a non-amd64 architecture, the template adds a COPY instruction to copy an architecture-specific static QEMU binary into the image. The resulting Dockerfile is built into an image called weave:${VERSION} if the target architecture is amd64, or weave${ARCHITECTURE}:${VERSION} if not.
The other templates create Dockerfiles that select either the weave:${VERSION} or the weave${ARCHITECTURE}:${VERSION} image as the base, depending on the target architecture.
Next, the generated Dockerfiles are used to build images. The images are tagged with several labels. One of these labels is org.opencontainers.image.revision, whose value is supposed to be a Git commit hash from which the image was built. It is passed in through a Dockerfile argument called revision, and can be supplied in the overall build process through the Makefile parameter GIT_REVISION. By default, this is picked up by running git rev-parse HEAD in the current directory.
Once built, the images are tagged as ${ACCOUNTNAME}/${IMAGENAME}:latest if the target architecture is amd64, or ${ACCOUNTNAME/${IMAGENAME}${ARCHITECTURE}:latest if the target architecture is anything else. The account name in the tag can be controlled using the Makefile parameter DOCKERHUB_USER.
The Makefile includes rules to push these images, which involve pushing all architecture-specific images, and then pushing a multi-architecture manifest.
The Makefile also includes rules to build a Docker plugin, and to run tests.
| Name | Description | Default |
|---|---|---|
| ARCH | The build target architecture. Can be one of: amd64 arm arm64 ppc64le s390x |
amd64 |
| BUILD_IN_CONTAINER | true if the build is to be done in a container created from a build container image, false if it is to be done on the local machine. |
true |
| ALPINE_BASEIMAGE | The base image for all generated images. | alpine:3.10 |
| GIT_REVISION | The git commit hash used as the value for a label called org.opencontainers.image.revision in all generated images. |
Result of git rev-parse HEAD |
| DOCKERHUB_USER | The registry/account used to tag all generated images | weaveworks |