As we found out while debugging <https://issues.guix.gnu.org/60010>, the
Shepherd 0.9.3, with its ‘system*’ replacement (aka. ‘spawn-command’),
makes it very hard to spawn a command with different environment
variables.
The following options don’t work:
• Changing shepherd’s own environment variables with ‘setenv’ for
instance: ‘spawn-command’ calls ‘fork+exec-command’, whose default
#:environment-variables is provided by the
‘default-environment-variables’ parameter, which gets its default
value at when shepherd starts. There’s no environment variable
inheritance, contrary to the real ‘system*’.
• Parameterizing ‘default-environment-variables’:
(parameterize ((default-environment-variables …))
(system* …))
That won’t work because ‘spawn-command’ delegates to the process
monitoring fiber, which has a different dynamic state and thus
doesn’t see this change.
• Even a plain (set! default-environment-variables …) won’t work,
probably due to inlining within (shepherd services).
I think we’ll have to add a parameter to ‘spawn-command’ to specify
environment variables.
Ludo’.
