[Bug] Misleading error message while processing dns.extra_records_path

[nblock]

Is this a support request?

• This is not a support request

Is there an existing issue for this?

• I have searched the existing issues

Current Behavior

Headscale prints an error message about unmarshalling records from dns.extra_records_path even though records are processed and streamed to nodes just fine.

Expected Behavior

Only print an error message when something went wrong permanently and cannot be recovered. Essentially transient errors happening while the file is written should be hidden. A user with the default log level has the impression that something is broken.

Steps To Reproduce

1. Set dns.extra_records_path to some path
2. Write to the file with: echo '[{"name":"grafana.myvpn.example.com","type":"A","value":"100.64.0.1"}]' | jq -cS > .headscale-dns/extra.json. Using this command triggers the error message reliably while headscale processes the changes correctly.
3. Headscale logs:

2024-12-14T19:28:11+01:00 TRC ../runner/work/headscale/headscale/hscontrol/dns/extrarecords.go:87 > extra records received filewatch event op=WRITE path=.headscale-dns/extra.json
2024-12-14T19:28:11+01:00 ERR ../runner/work/headscale/headscale/hscontrol/dns/extrarecords.go:115 > reading extra records from path: .headscale-dns/extra.json error="unmarshalling records, content: \"\": unexpected end of JSON input"
2024-12-14T19:28:11+01:00 TRC ../runner/work/headscale/headscale/hscontrol/dns/extrarecords.go:87 > extra records received filewatch event op=WRITE path=.headscale-dns/extra.json
2024-12-14T19:28:11+01:00 TRC ../runner/work/headscale/headscale/hscontrol/dns/extrarecords.go:134 > extra records updated from path, count old: 1, new: 1 records=[{"Name":"grafana.myvpn.example.com","Type":"A","Value":"100.64.0.2"}]
2024-12-14T19:28:11+01:00 TRC ../runner/work/headscale/headscale/hscontrol/poll.go:644 > received stream update: StateFullUpdate  node=n1 node.id=1 omitPeers=false readOnly=false stream=true
2024-12-14T19:28:11+01:00 TRC ../runner/work/headscale/headscale/hscontrol/poll.go:644 > Sending Full MapResponse node=n1 node.id=1 omitPeers=false readOnly=false stream=true
2024-12-14T19:28:11+01:00 TRC finished writing mapresp to node mkey=mkey:94b730090613b46fe0f4a0a51518c2a585c63641a25a24ec419881be55015b0d node=n1 timeSpent=0.095543
2024-12-14T19:28:11+01:00 TRC ../runner/work/headscale/headscale/hscontrol/poll.go:644 > update sent node=n1 node.id=1 omitPeers=false readOnly=false stream=true

Environment

- OS: Arch
- Headscale version: 0.24.0-beta.1
- Tailscale version: -

Runtime environment

• Headscale is behind a (reverse) proxy
• Headscale runs in a container

Anything else?

No response