Running multiple versions side by side¶

You can run independent versions of milk side-by-side on the same machine, but there's some environment overlap that you must be careful about.

1. Installation and environment¶

Clone two different copies (or, use git worktrees):

cd ~/src
git clone --recursive https://github.com/milk-org/milk milk-1
git clone --recursive https://github.com/milk-org/milk milk-2

Then compile and install:

mkdir -p ~/src/milk-1/_build ~/src/milk-2/_build
cd ~/src/milk-1/_build
cmake -DCMAKE_INSTALL_PREFIX=/usr/local/milk-1 ..
sudo make install

cd ~/src/milk-2/_build
cmake -DCMAKE_INSTALL_PREFIX=/usr/local/milk-2 ..
sudo make install

And e.g. make milk-1 your system default:

sudo ln -sfn "/usr/local/milk-1/milk-<version>" /usr/local/milk

Legacy linker configuration

If you find references to using milk with configuring LD_LIBRARY_PATH and using ldconfig, these are obsolete and should be unnecessary (and conflicting!) with the current build/install workflow.

2. Clean environment¶

The environment conundrum

milk relies on environment variables and external tools. Expect:

tmux naming collisions
MILK_SHM_DIR and MILK_PROC_DIR collisions
MILK_ROOT and MILK_INSTALLDIR collisions in peripheral tools.

A lot more trouble ! Even if we override these environment variables in a shell, the following will happen:

Humanic shell:
    override MILK_SHM_DIR
    call fpsexec-<x> -tmux runstart (like this, or through milk pipelines)
 v-------
fpsexec in humanic shell:
    knows the correct overridden MILK_SHM_DIR
    dispatches fpsexec-<x> runstart (no tmux) into a tmux session
 v-------
tmux's shell
    Initializes bash and set MILK_SHM_DIR to the default !
    executes <fullpath>/fpsexec-<x> runstart
            The exec, linkage paths are correct, but the environment is the default !

At the end of this, the execution environment has NOT received the environment override.

In the installation, we set for the shell:

Variable	Example	Purpose
`MILK_ROOT`	`/home/user/src/milk`	Source code directory
`MILK_INSTALLDIR`	`/usr/local/milk`	Installation directory
`MILK_SHM_DIR`	`/milk/shm`	Shared memory directory

The trick is to not override a variable that may be passed to the shell; this is done by

export MILK_SHM_DIR="${MILK_SHM_DIR:-/milk/shm}"
export MILK_INSTALLDIR="${MILK_INSTALLDIR:-/usr/local/milk}"
export MILK_ROOT="${MILK_ROOT:-/home/user/src/milk}"

to which we add a tmux override, so that another tmux server takes over entirely:

export TMUX_TMPDIR=/tmp/milk-my-second-devel-version/
mkdir -p ${TMUX_TMPDIR}
unset TMUX

Now with all of the above set, the new tmux server receives the correct environment, including the milk variables overriding the defaults. When bash loads in the tmux sessions, it does not override the preferred environment.

milk-env-switch ?

We still need to switch environments in each top-level terminal interacted with by a human, or by tooling that will interact with the tmux. We should propose a milk-env-switch #id that does that and can be one-lined, or combined with a virtualenv of some kind.