Add config option to disable reporting

[sed-i]

Issue

By default, grafana-agent sends out anonymous usage stats. This may be undesired in hardened environments.

Solution

Add a charm config option to disable the reporting (ref). The config option is named the same was as in the grafana-k8s charm (see grafana/354).

Drive-by fixes:

• Use a patch file instead of a symlink for packing the 24.04 charm. Until this change we often forgot to update the 24.04 charmcraft yaml with the changes made to the 22.04 charmcraft.yaml.
• Fetch-lib cos-agent.
• Write config file before the snap is installed, otherwise the charm briefly goes into error state. Related: When a snap fails to restart for some reason, e.g. "Start request repeated too quickly", log messages do not reflect the reason operator-libs-linux#136

In tandem with:

• Add config option for disabling reporting grafana-agent-snap#78
• Fix classic snap grafana-agent-snap#80
• Fix classic snap grafana-agent-snap#81

Related:

• Add config option for disabling reporting grafana-agent-k8s-operator#326
• Add config option for disabling reporting grafana-k8s-operator#354
• feat: disable-reporting juju config option loki-k8s-operator#471

Context

• ADR

Testing Instructions

Deploy the following bundle:

default-base: [email protected]/stable
applications:
  ga20:
    charm: local:grafana-agent-1
    base: [email protected]/stable
  ga22:
    charm: local:grafana-agent-4
  u20:
    charm: ubuntu
    channel: latest/stable
    revision: 25
    base: [email protected]/stable
    num_units: 1
    to:
    - "22"
    constraints: arch=amd64
    storage:
      block: loop,100M
      files: rootfs,100M
  u22:
    charm: ubuntu
    channel: latest/stable
    revision: 25
    num_units: 1
    to:
    - "23"
    constraints: arch=amd64
    storage:
      block: loop,100M
      files: rootfs,100M
machines:
  "22":
    constraints: arch=amd64
    base: [email protected]/stable
  "23":
    constraints: arch=amd64
relations:
- - u20:juju-info
  - ga20:juju-info
- - u22:juju-info
  - ga22:juju-info

And curl the readiness endpoint:

> juju ssh ga20/1 curl localhost:12345/-/ready
Agent is Ready.
Connection to 10.3.37.71 closed.
> juju ssh ga22/1 curl localhost:12345/-/ready
Agent is Ready.
Connection to 10.3.37.193 closed.

Upgrade Notes

[sed-i]

Revs updated per https://github.com/canonical/grafana-agent-snap/actions/runs/11920885947