apt packages from config

[yanksyoon]

Applicable spec: N/A

Overview

Allow installing apt packages through configuration.

Rationale

To automate setup of agents.

Juju Events Changes

• on config changed: install apt packages from charm config.

Module Changes

• service: Added method to install apt packages.

Library Changes

None.

Checklist

• The charm style guide was applied
• The contributing guide was applied
• The changes are compliant with ISD054 - Managing Charm Complexity
• The documentation is generated using src-docs
• The documentation for charmhub is updated
• The PR is tagged with appropriate label (urgent, trivial, complex)

[yhaliaw]

Does service.PackageInstallError excludes network-related errors?
I would think network-related error would not need to go to block state.

[yanksyoon]

The apt lib provided uses subprocess.run under the hood so there's not much ways to differentiate the network related errors. What the lib does expose are errors like PackageNotFound, which was suitable for user to unblock by re-configuring the config option.
Do you think ErrorState might be more well-fitting for both cases?

[yhaliaw]

For error that requires config change, it should be in block state.
If the PackageNotFound only is thrown when user need to unblock it, then it should use BlockedState.

For network-related it should be error state.

[yanksyoon]

Since network related errors would not be caught (subprocess error would be raised here) - it should fallthrough and go into ErroredState automatically.

[github-actions]

Test coverage for 442c9bd

Name                    Stmts   Miss Branch BrPart  Cover   Missing
-------------------------------------------------------------------
src/agent_observer.py      42      0      4      0   100%
src/charm.py               69      0     10      0   100%
src/charm_state.py         66      4     12      1    94%   116, 191-193
src/service.py            109      5     16      5    92%   95-97, 109->121, 154, 186, 223->227, 225->223
-------------------------------------------------------------------
TOTAL                     286      9     42      6    95%

Static code analysis report

Run started:2024-05-09 06:11:22.008866

Test results:
  No issues identified.

Code scanned:
  Total lines of code: 1260
  Total lines skipped (#nosec): 0
  Total potential issues skipped due to specifically being disabled (e.g., #nosec BXXX): 0

Run metrics:
  Total issues (by severity):
  	Undefined: 0
  	Low: 0
  	Medium: 0
  	High: 0
  Total issues (by confidence):
  	Undefined: 0
  	Low: 0
  	Medium: 0
  	High: 0
Files skipped (0):

[yanksyoon]

Closing - the apt packages should be installed via jobs