Feature request: Configuration validation

[exFalso]

Hi, it would be great if the agent could load and validate its configuration without actually starting. This would enable a static check of the configuration before deployment.

[rfratto]

Hey! I agree this would be nice, but it could be pretty difficult to implement generally. For example, there's not a standard remote_write URL that can be used to validate credentials. Other validations might only be possible to check at runtime, such as if your relabel_rules are valid.

What types of validations are you interested in specifically?

[exFalso]

(Wow fast response!)

The reason I thought of this is that I got an "unmarshall" error for my yaml (I think it was the server http_listen_port setting) because I used a = instead of a :. I added a yamllint pass but that doesn't catch this error, it's specific to grafana agent.
So I think perhaps a good tradeoff for validation is to simply deserialize the config to make sure the types align.

[rfratto]

Ahh, I see now. We can totally do this! Would you care if it's a part of agentctl as a check-config command? Or would you prefer it to be some kind of a flag on the main Agent binary?

(FWIW, today, agentctl isn't included in the main agent image, but we can change this too)

[exFalso]

Both would make sense. We actually build/package the agent from source and include the agentctl binary, so either works for us.