Limit dynamic operation dir APIs to main device #2409

[albinsuresh]

Proposed changes

1. Add operations support for nested child devices by keeping their supported operations in the same /etc/tedge/operations/c8y directory where the main device and immediate child devices keep their operation files.
2. Stop interpreting all directories under the operations directory as immediate child devices, and registering them on startup, resulting in the reported bug.
3. Limit the dynamic update of the supported operations list via file updates to this directory only to the main device. The supported list of child devices are updated only when they declare their supported operations via MQTT.

Types of changes

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Improvement (general improvements like code refactoring that doesn't explicitly fix a bug or add any new functionality)
• Documentation Update (if none of the other choices apply)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Paste Link to the issue

#2409

Checklist

• I have read the CONTRIBUTING doc
• I have signed the CLA (in all commits with git commit -s)
• I ran cargo fmt as mentioned in CODING_GUIDELINES
• I used cargo clippy as mentioned in CODING_GUIDELINES
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)

Further comments

[codecov]

Codecov Report

Attention: 14 lines in your changes are missing coverage. Please review.

Comparison is base (00c14eb) 75.9% compared to head (0ece474) 75.8%.

Additional details and impacted files

Files	Coverage Δ
crates/extensions/c8y_mapper_ext/src/config.rs	45.7% <100.0%> (+1.4%)	⬆️
crates/extensions/c8y_mapper_ext/src/tests.rs	91.8% <96.0%> (+0.1%)	⬆️
crates/extensions/c8y_mapper_ext/src/converter.rs	81.0% <68.7%> (-0.7%)	⬇️
crates/extensions/c8y_mapper_ext/src/actor.rs	80.3% <53.3%> (+1.6%)	⬆️

... and 4 files with indirect coverage changes

[github-actions]

Robot Results

✅ Passed	❌ Failed	⏭️ Skipped	Total	Pass %	⏱️ Duration
385	0	3	385	100	57m37.867999999s

[rina23q]

Looks good, however, I want to review one more round after I get more insights about handling of custom operations.

P.S. I think this PR also needs to update user guide. For example, https://thin-edge.github.io/thin-edge.io/operate/c8y/supported_operations/#adding-new-operations is stating as below:

To add a new operation to a child device, create a new file in /etc/tedge/operations/c8y/ directory as below.
sudo -u tedge touch /etc/tedge/operations/c8y//c8y_Restart
Now the new operation will be automatically added to the list of child supported operations and will be sent to the cloud.

This is no longer applicable.

[didier-wenzek]

There is something a bit weird/overly complex/useless here.

The process_inotify_events method carefully build a DiscoverOp with the details of the operation update,
but the process_operation_update_message calls try_process_operation_update_messaDiscoverOpge which ignores all the message: DiscoverOp content except for the message.ops_dir which is always equals to the converter.ops_dir.

[rina23q]

Code and tests look good.

However, I think the doc is still not clear enough for the users who want to add a custom operation for child devices. I think we should mention
a. they can create a custom operation file for child devices
b. however, they need to declare its capability via MQTT message (probably link to the capability doc is enough)

[albinsuresh]

Code and tests look good.

However, I think the doc is still not clear enough for the users who want to add a custom operation for child devices. I think we should mention a. they can create a custom operation file for child devices b. however, they need to declare its capability via MQTT message (probably link to the capability doc is enough)

Even though we support that, I intentionally left that out from the doc as the goal is to eventually deprecate this whole file-system based API and replace it completely with workflows. So, I didn't want to highlight a feature in the 1.0 doc that'll be deprecated soon. Especially since the existing Adding new custom operation section does not explicitly mention support for child devices.

[didier-wenzek]

The code is doing what is expected. However, I have comments related to docs & tests.

[didier-wenzek]

Approved