EdgeX Config Provider Example

This is an example config provider for EdgeX service Snaps.

A good starting point to get familiar with the concepts is to visit Content Interface documentation and the given examples.

Crafting config provider snap

To help understand how a provider can be setup to provide configurations to multiple snaps, this repository contains the following:

• examples directory with sample config files for some services
• snap/snapcraft.yaml file used to create the snap that can provide those config files

Build and install the snap:

snapcraft
sudo snap install ./edgex-config-provider-example_2.3_amd64.snap --dangerous

Connect to the provided slots

The plugs of consumer snaps need to be manually connected to the slots provided by this snaps. The plugs stay connected during updates.

Note - content interfaces from snaps installed from the Snap Store that have the same publisher connect automatically. For more information on snap content interfaces please refer to the snapcraft.io Content Interface documentation.

In this example, the device-virtual-config plug from edgex-device-virtual snap is being connected to the slot with the same name of this snap (i.e. edgex-config-provider):

sudo snap connect edgex-device-virtual:device-virtual-config edgex-config-provider-example:device-virtual-config

Note that one of the conditions to have automatic connection is to have matching plug and slot names.

Check the connections:

$ sudo snap connections edgex-config-provider-example
Interface               Plug                             Slot                               Notes
content[device-config]  edgex-device-mqtt:device-config  edgex-config-provider:device-mqtt  manual

Debugging Tips

Mount points

The source directories defined on producers are mounted INSIDE (not on) the target path set in consumer's plug.

List exposed file

E.g. device-mqtt:

$ tree /snap/edgex-config-provider/current/device-mqtt/
/snap/edgex-config-provider/current/device-mqtt/
└── res
    ├── configuration.toml
    ├── devices
    │   └── mqtt.test.device.toml
    ├── profiles
    │   └── mqtt.test.device.profile.yml
    └── README.md

3 directories, 4 files

List mounted files

Note - the mounted files will not be available on the host file system and trying to list /var/snap/device-mqtt/current will not show anything. See https://askubuntu.com/a/841787/366811

The files can be listed from inside the consumer snap's shell environment. To enter the shell environment of device-mqtt and list mounted paths:

$ sudo snap run --shell edgex-device-mqtt.device-mqtt
root@***# find /var/snap/edgex-device-mqtt/current/config
/var/snap/edgex-device-mqtt/current/config
/var/snap/edgex-device-mqtt/current/config/device-mqtt
/var/snap/edgex-device-mqtt/current/config/device-mqtt/res
/var/snap/edgex-device-mqtt/current/config/device-mqtt/res/README.md
/var/snap/edgex-device-mqtt/current/config/device-mqtt/res/configuration.toml
/var/snap/edgex-device-mqtt/current/config/device-mqtt/res/devices
/var/snap/edgex-device-mqtt/current/config/device-mqtt/res/devices/mqtt.test.device.toml
/var/snap/edgex-device-mqtt/current/config/device-mqtt/res/profiles
/var/snap/edgex-device-mqtt/current/config/device-mqtt/res/profiles/mqtt.test.device.profile.yml
...