How to build a Tango image using cppTango

When building OCI images, it is recommended to use a separate build stage from the runtime stage to avoid including build-time dependencies in the final image.

ska-tango-images provides ska-tango-images-tango-cpp as a build image for cppTango-based applications.

For the runtime image it is recommended to use either ska-tango-images-tango-admin or ska-tango-images-tango-base. ska-tango-images-tango-admin provides the tango_admin utility which is often useful to include in the image, however, if this utility is not required ska-tango-images-tango-base is provided as a leaner alternative.

Dockerfile Template

The following Dockerfile template can be used to build a C++ application linking against libtango.so, using the ska-tango-images-tango-admin base image:

ARG BUILD_IMAGE=artefact.skao.int/ska-tango-images-tango-cpp:10.0.2
ARG BASE_IMAGE=artefact.skao.int/ska-tango-images-tango-admin:1.27.0
FROM $BUILD_IMAGE AS build

# build and install application

FROM $BASE_IMAGE
COPY --from=build </path/to/installed/application> /usr/local/bin

LABEL int.skao.image.team=<my-team> \
      int.skao.image.authors=<author> \
      int.skao.image.url=<gitlab url> \
      description=<description> \
      license=<license>

Note

It is recommended to provide BUILD_IMAGE and BASE_IMAGE arguments rather than hard-coding them directly. These arguments can be used by tools such as the SKA Tango Test Bench to test out different versions of build and base images.

The libtango.so library can be found at /usr/local/lib/libtango.so in both ska-tango-images-tango-admin and ska-tango-images-tango-cpp. This will need to be found at both build-time and runtime, if using CMake to build your C++ application, this can be achieved by passing -DCMAKE_INSTALL_PREFIX=/usr/local/ -DCMAKE_INSTALL_RPATH=/usr/local/lib to cmake at configure time.

Example

The following Dockerfile builds a TangoTest image using ska-tango-images-tango-base as a base image rather than ska-tango-images-tango-admin, which is used by ska-tango-images-tango-test.

ARG BUILD_IMAGE=artefact.skao.int/ska-tango-images-tango-cpp:10.0.2
ARG BASE_IMAGE=artefact.skao.int/ska-tango-images-tango-base:0.3.1
FROM $BUILD_IMAGE AS build

RUN set -xe; \
 apt-get update; \
 apt-get install -y --no-install-recommends \
     cmake \
     git

RUN set -xe; \
    git clone --depth=1 --branch=3.10 --recursive -c advice.detachedHead=false \
        https://gitlab.com/tango-controls/TangoTest.git /usr/src/TangoTest;  \
    cmake -S/usr/src/TangoTest -B/build -DCMAKE_BUILD_TYPE=Release \
        -DCMAKE_INSTALL_PREFIX=/usr/local/ -DCMAKE_INSTALL_RPATH=/usr/local/lib; \
    make  -j$(nproc) -C/build install

FROM $BASE_IMAGE
COPY --from=build /usr/local/bin/TangoTest /usr/local/bin

ENTRYPOINT ["TangoTest"]

LABEL int.skao.image.team="Team Example" \
      int.skao.image.authors="an@example.com" \
      int.skao.image.url="https://gitlab.com/example" \
      description="This is just an example and these labels should be updated" \
      license="BSD-3-Clause"

To build and run an image using this example, copy the above into a file named Dockerfile and run the following commands from a terminal inside the same directory:

docker image build -t my-tango-test .
docker run --rm --env TANGO_HOST=$TANGO_HOST --net=host my-tango-test test

This will launch a TangoTest device server connecting to your TANGO_HOST.