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Using direnv to develop Wire-Cell/LArSoft software

Overview

This document describes a method to simplify developing software in a joint Wire-Cell/LArSoft (WCLS) environment. Some goals:

  • Make it easy to get started on a new project.
  • Make it easy to return to an old project.
  • Smooth out the sometimes bumpy FNAL software development tooling.
  • Allow developers to use their usual development tools from their host OS.
  • Support multiple, independent development projects.

The main ingredients are:

  • A container built with wire-cell-containers package to provide an officially supported OS (Scientific Linux 7) most minimally to provide build and run time environments for the software under development.
  • Additional OS packages in the container to simplify build and run time usage.
  • A reasonable and “safe” generic container shell environment.
  • Layered shell environment management with context memory via direnv.

Container

See the main README file.

Prepare host working area

We’ll put all projects in a common root:

mkdir -p ~/dev/wcls
cd ~/dev/wcls

Start a container

host$ singularity shell --cleanenv --bind /cvmfs /path/to/wirecell-sluser.sif
Singularity> source /etc/profile
[wirecell-sluser] bviren@hierocles:~/dev/wcls$

If a directory outside of $HOME is used for the working area, it must be added as an additional --bind if it is to be accessed inside the container.

Hierarchical development tree

Once inside the container, you are free to organize your development area as you wish. However, the container provides support to use direnv for a well organized area and environment management. The basic idea is to have three levels of directories with each mapping to a more specific environment:

experiment
defines the “experiment” level setup, eg “dune”.
umbrella
defines an “umbrella” or “seed” package. It particular, defines the things like UPS flavor and qualifiers (compiler).
project
another umbrella or seed package that mrb uses to determine whatever mrb does.

This results is a directory tree like:

<experiment>/<umbrella>/<project>/mrb/srcs/{repo,...}

Entering each of the first three directories will configure your shell environment to use that context. Below we will give an example.

Example

The following produces a tree with the leaf configured for developing larwirecell in the context of DUNE software.

rm -rf dune/
mkdir -p dune/dunesw/toff

cat <<EOF > dune/.envrc
wcls_experiment dune
EOF

cat <<EOF > dune/dunesw/.envrc
source_up
wcls_project dunesw v09_76_00d00 e20:prof
EOF

cat <<EOF > dune/dunesw/toff/.envrc
source_up
wcls_develop larsoft
wcls_devsrc larwirecell -b feature/bv_trackid_torigin -g brettviren
EOF

This may be pasted into your container shell session. Entering the leaf then activates the environment:

[wirecell-sluser] bviren@hierocles:~/dev/wcls$ cd dune/dunesw/toff
direnv: error /home/bviren/dev/wcls/dune/dunesw/toff/.envrc is blocked. Run `direnv allow` to approve its content
[wirecell-sluser] bviren@hierocles:~/dev/wcls/dune/dunesw/toff$ direnv allow
....
[wirecell-sluser] bviren@hierocles:~/dev/wcls/dune/dunesw/toff$ art --version
art 3.12.00
[wirecell-sluser] bviren@hierocles:~/dev/wcls/dune/dunesw/toff$ ls -l mrb/srcs/
total 8
-rw-rw-r-- 1 bviren bviren 1096 Aug 14 10:54 CMakeLists.txt
drwxrwxr-x 6 bviren bviren 4096 Aug 14 10:54 larwirecell

Note, after direnv allow you will very likely see a warning in red like:

direnv: ([/usr/local/bin/direnv export bash]) is taking a while to execute. Use CTRL-C to give up.

Just wait. This is life with UPS and CVMFS. After trhe local CVMFS cache is populated, subsequent repeats should be faster.

$ cd
$ cd -

Using the project

With the above in place:

cd dune/dunesw/toff
direnv allow  # if prompted

Now ready to run and/or build the local sources

art --version
mrb b