feat(snap): Add snap packaging

.gitignore

@@ -26,4 +26,14 @@ LintOutput.json
 device-usb-camera
 run
 
-#VERSION
+VERSION
+
+# snap files
+*.snap
+*.assert
+prime/
+stage/
+parts/
+squashfs-root/
+coverage.out
+VERSION

cmd/res/devices/general.usb.camera.toml.example

@@ -0,0 +1,9 @@
+[[DeviceList]]
+  Name = "example-camera"
+  ProfileName = "USB-Camera-General"
+  Description = "Example Camera"
+  Labels = [ "device-usb-camera-example" ]
+  [DeviceList.Protocols]
+    [DeviceList.Protocols.USB]
+    Path = "/dev/video0"
+    AutoStreaming = "false"

snap/README.md

@@ -0,0 +1,85 @@
+# EdgeX USB Camera Device Service Snap
+[![edgex-device-usb-camera](https://snapcraft.io/edgex-device-usb-camera/badge.svg)](https://snapcraft.io/edgex-device-usb-camera)
+
+This directory contains the snap packaging of the EdgeX USB Camera device service.
+
+The snap is built automatically and published on the Snap Store as [edgex-device-usb-camera].
+
+For usage instructions, please refer to Device Camera section in [Getting Started using Snaps][docs].
+
+## Build from source
+Execute the following command from the top-level directory of this repo:
+```
+snapcraft
+```
+
+This will create a snap package file with `.snap` extension. It can be installed locally by setting the `--dangerous` flag:
+```bash
+sudo snap install --dangerous <snap-file>
+```
+
+The [snapcraft overview](https://snapcraft.io/docs/snapcraft-overview) provides additional details.
+
+### Obtain a Secret Store token
+<!-- The `edgex-secretstore-token` snap slot makes it possible to automatically receive a token from a locally installed platform snap.-->
+
+If the snap is built and installed locally, the interface will not auto-connect. You can check the status of the connections by running the `snap connections edgex-device-usb-camera` command.
+
+Notes:
+- The auto connection will not happen right now because the snap publisher isn't same as the `edgexfoundry` platrform snap (i.e. Canonical).
+- The service isn't yet included in the secrets list of the platform snap.
+Add the device service to list of services which have tokens generated for them:
+```
+# Additional secret store tokens
+EXISTING=$(snap get edgexfoundry apps.security-secretstore-setup.config.add-secretstore-tokens)
+snap set edgexfoundry apps.security-secretstore-setup.config.add-secretstore-tokens="$EXISTING,device-usb-camera"
+
+# Additional known secrets
+EXISTING=$(snap get edgexfoundry apps.security-secretstore-setup.config.add-known-secrets)
+snap set edgexfoundry apps.security-secretstore-setup.config.add-known-secrets="$EXISTING,redisdb[device-usb-camera]"
+
+# Additional registry ACL roles
+EXISTING=$(snap get edgexfoundry apps.security-bootstrapper.config.add-registry-acl-roles)
+snap set edgexfoundry apps.security-bootstrapper.config.add-registry-acl-roles="$EXISTING,device-usb-camera"
+
+# Run the bootstrappers:
+snap start edgexfoundry.security-secretstore-setup
+snap start edgexfoundry.security-consul-bootstrapper 
+```
+
+To manually connect and obtain a token:
+```bash
+sudo snap connect edgexfoundry:edgex-secretstore-token edgex-device-usb-camera:edgex-secretstore-token
+```
+
+Please refer [here][secret-store-token] for further information.
+
+### Connect the camera interface
+The `camera` interface is currently not automatically connected. To connect manually:
+```
+snap connect edgex-device-usb-camera:camera :camera
+```
+
+[edgex-device-usb-camera]: https://snapcraft.io/edgex-device-usb-camera
+[docs]: https://docs.edgexfoundry.org/2.2/getting-started/Ch-GettingStartedSnapUsers/#device-usb-camera
+[secret-store-token]: https://docs.edgexfoundry.org/2.2/getting-started/Ch-GettingStartedSnapUsers/#secret-store-token
+
+# Issues
+The snap is 115 MB, exactly same as the docker image.
+
+It may be possible to reduce the size by removing extra shared library object files.
+
+See:
+```
+./device-usb-camera$ du -a -d 1 squashfs-root/usr/lib/x86_64-linux-gnu/ | sort -n -r | head -n 10
+297884  squashfs-root/usr/lib/x86_64-linux-gnu/
+89352   squashfs-root/usr/lib/x86_64-linux-gnu/libLLVM-12.so.1
+43020   squashfs-root/usr/lib/x86_64-linux-gnu/dri
+27392   squashfs-root/usr/lib/x86_64-linux-gnu/libicudata.so.66.1
+15732   squashfs-root/usr/lib/x86_64-linux-gnu/libx265.so.179
+14208   squashfs-root/usr/lib/x86_64-linux-gnu/libavcodec.so.58.54.100
+14196   squashfs-root/usr/lib/x86_64-linux-gnu/libcodec2.so.0.9
+9380    squashfs-root/usr/lib/x86_64-linux-gnu/librsvg-2.so.2.47.0
+4808    squashfs-root/usr/lib/x86_64-linux-gnu/libflite_cmu_time_awb.so.2.1
+4712    squashfs-root/usr/lib/x86_64-linux-gnu/libflite_cmu_us_rms.so.2.1
+```