Module updates

The core action update-module is the entry point of a module instance update. It can run the update on multiple instances of the same module at the same time.

The core then invokes the module update-module action. Each module instance is responsible for updating itself. The core already provides an extendable implementation of the update-module action for the module agent. The base implementation

  • pulls the module image and additional service images
  • extracts and installs the module imageroot under the ${AGENT_INSTALL_DIR}
  • runs systemctl --user daemon-reload, to refresh Systemd with new unit definitions
  • updates the environment variables, keeping track of PREV_* values
  • runs update scripts installed with the new image, under ${AGENT_INSTALL_DIR}/update-module.d/
  • removes stale container images

Modules can provide update scripts to handle upgrade paths like restarting services and database schema migrations. Executable scripts can be placed inside imageroot/update-module.d which will be then extracted to ${AGENT_INSTALL_DIR}/update-module.d. Scripts execution occurs in alphabetical order. If a script aborts with an exit code, a warning is printed. Example of a script that restarts a Systemd service, imageroot/update-module.d/20restart:

systemctl --user try-restart mymodule.service

Make sure the 20restart is executable, otherwise it is ignored.

To update an instance from command line, use:

 api-cli run update-module --data '{"module_url":"","instances":["mymodule1"]}'

If the given module_url is already present in the local Podman storage, no remote download occurs and the local image is used instead. During development this might be unwanted and to work around this behavior set the flag "force": true to the update-module action:

api-cli run update-module --data '{"module_url":"","instances":["mymodule1"],"force":true}'