Today, I had to figure out how to format a Grafana datasource with a custom CA literally for the 99th time. How can this be so hard? Also, it doesn’t help that there is conflicting information on how to format certs in yaml even in the Grafana community threads. That’s always the first page I find about the topic. The second is the stackoverflow post on how to break strings in yaml which sends you down a totally wrong path.
The error messages you get from the Grafana server logs are also not very helpful, given you can access them:

Failed to call resource" error="Get \"https:///tnglab.fritz.box/prometheus...": x509: certificate signed by unknown authority

Well, thanks for nothing!

So, once and for all! This is the way:

---
apiVersion: 1
datasources:
  - name: Prometheus
    type: prometheus
    url: https://tnglab.fritz.box/prometheus
    orgId: 1
    isDefault: true
    editable: false
    access: proxy
    basicAuth: true
    basicAuthUser: promuser
    jsonData:
      tlsAuthWithCACert: true
    secureJsonData:
      basicAuthPassword: change-me
      tlsCACert: |
        -----BEGIN CERTIFICATE-----
        MIIG7jCCBNagAwIBAgIBDzANBgkqhkiG9w0BAQsFADB5MRAwDgYDVQQKEwdSb290
        IENBMR4wHAYDVQQLExVodHRwOi8vd3d3LmNhY2VydC5vcmcxIjAgBgNVBAMTGUNB
        IENlcnQgU2lnbmluZyBBdXRob3JpdHkxITAfBgkqhkiG9w0BCQEWEnN1cHBvcnRA
        Y2FjZXJ0Lm9yZzAeFw0wMzAzMzAxMjI5NDlaFw0zMzAzMjkxMjI5NDlaMHkxEDAO
        BgNVBAoTB1Jvb3QgQ0ExHjAcBgNVBAsTFWh0dHA6Ly93d3cuY2FjZXJ0Lm9yZzEi
        MCAGA1UEAxMZQ0EgQ2VydCBTaWduaW5nIEF1dGhvcml0eTEhMB8GCSqGSIb3DQEJ
        ARYSc3VwcG9ydEBjYWNlcnQub3JnMIICIjANBgkqhkiG9w0BAQEFAAOCAg8AMIIC
        CgKCAgEAziLA4kZ97DYoB1CW8qAzQIxL8TtmPzHlawI229Z89vGIj053NgVBlfkJ
        8BLPRoZzYLdufujAWGSuzbCtRRcMY/pnCujW0r8+55jE8Ez64AO7NV1sId6eINm6
        zWYyN3L69wj1x81YyY7nDl7qPv4coRQKFWyGhFtkZip6qUtTefWIonvuLwphK42y
        fk1WpRPs6tqSnqxEQR5YYGUFZvjARL3LlPdCfgv3ZWiYUQXw8wWRBB0bF4LsyFe7
        w2t6iPGwcswlWyCR7BYCEo8y6RcYSNDHBS4CMEK4JZwFaz+qOqfrU0j36NK2B5jc
        G8Y0f3/JHIJ6BVgrCFvzOKKrF11myZjXnhCLotLddJr3cQxyYN/Nb5gznZY0dj4k
        epKwDpUeb+agRThHqtdB7Uq3EvbXG4OKDy7YCbZZ16oE/9KTfWgu3YtLq1i6L43q
        laegw1SJpfvbi1EinbLDvhG+LJGGi5Z4rSDTii8aP8bQUWWHIbEZAWV/RRyH9XzQ
        QUxPKZgh/TMfdQwEUfoZd9vUFBzugcMd9Zi3aQaRIt0AUMyBMawSB3s42mhb5ivU
        fslfrejrckzzAeVLIL+aplfKkQABi6F1ITe1Yw1nPkZPcCBnzsXWWdsC4PDSy826
        YreQQejdIOQpvGQpQsgi3Hia/0PsmBsJUUtaWsJx8cTLc6nloQsCAwEAAaOCAX8w
        ggF7MB0GA1UdDgQWBBQWtTIb1Mfz4OaO873SsDrusjkY0TAPBgNVHRMBAf8EBTAD
        AQH/MDQGCWCGSAGG+EIBCAQnFiVodHRwOi8vd3d3LmNhY2VydC5vcmcvaW5kZXgu
        cGhwP2lkPTEwMFYGCWCGSAGG+EIBDQRJFkdUbyBnZXQgeW91ciBvd24gY2VydGlm
        aWNhdGUgZm9yIEZSRUUgaGVhZCBvdmVyIHRvIGh0dHA6Ly93d3cuY2FjZXJ0Lm9y
        ZzAxBgNVHR8EKjAoMCagJKAihiBodHRwOi8vY3JsLmNhY2VydC5vcmcvcmV2b2tl
        LmNybDAzBglghkgBhvhCAQQEJhYkVVJJOmh0dHA6Ly9jcmwuY2FjZXJ0Lm9yZy9y
        ZXZva2UuY3JsMDIGCCsGAQUFBwEBBCYwJDAiBggrBgEFBQcwAYYWaHR0cDovL29j
        c3AuY2FjZXJ0Lm9yZzAfBgNVHSMEGDAWgBQWtTIb1Mfz4OaO873SsDrusjkY0TAN
        BgkqhkiG9w0BAQsFAAOCAgEAR5zXs6IX01JTt7Rq3b+bNRUhbO9vGBMggczo7R0q
        Ih1kdhS6WzcrDoO6PkpuRg0L3qM7YQB6pw2V+ubzF7xl4C0HWltfzPTbzAHdJtja
        JQw7QaBlmAYpN2CLB6Jeg8q/1Xpgdw/+IP1GRwdg7xUpReUA482l4MH1kf0W0ad9
        4SuIfNWQHcdLApmno/SUh1bpZyeWrMnlhkGNDKMxCCQXQ360TwFHc8dfEAaq5ry6
        cZzm1oetrkSviE2qofxvv1VFiQ+9TX3/zkECCsUB/EjPM0lxFBmu9T5Ih+Eqns9i
        vmrEIQDv9tNyJHuLsDNqbUBal7OoiPZnXk9LH+qb+pLf1ofv5noy5vX2a5OKebHe
        +0Ex/A7e+G/HuOjVNqhZ9j5Nispfq9zNyOHGWD8ofj8DHwB50L1Xh5H+EbIoga/h
        JCQnRtxWkHP699T1JpLFYwapgplivF4TFv4fqp0nHTKC1x9gGrIgvuYJl1txIKmx
        XdfJzgscMzqpabhtHOMXOiwQBpWzyJkofF/w55e0LttZDBkEsilV/vW0CJsPs3eN
        aQF+iMWscGOkgLFlWsAS3HwyiYLNJo26aqyWPaIdc8E4ck7Sk08WrFrHIK3EHr4n
        1FZwmLpFAvucKqgl0hr+2jypyh5puA3KksHF3CsUzjMUvzxMhykh9zrMxQAHLBVr
        Gwc=
        -----END CERTIFICATE-----
...

This example also includes basic auth. You’re welcome.

Common formatting errors

Just some errors I made myself over and over again.

It’s tlsCACert, not tlsCaCert

No, it’s not strict CamelCase!

Use the pipe for multiline input

Yes, it’s easy to forget. But start the certificate line like this: tlsCACert: |

Don’t use the greater than symbol

If you use the greater than symbol to start the certificate, all newlines will be removed. That’s not necessary and may not work.

Don’t try modifiers after the pipe

Like 2, -, etc… Just don’t!

Don’t use quotes instead of the pipe

They will not preserve the newlines.

Use the correct indentation

Use the same indentation method and depth throughout the file. The certificate starts one line below the tlsCACert: | and is indented one level more than the tlsCACert.

The certificate goes into the secureJsonData block

Yes, I know, for some reason the switch to turn the certificate check off tlsSkipVerify goes into the jsonData block. But the tlsCACert goes into the secureJsonData block.

Don’t forget the API version

apiVersion: 1 or newer if appropriate must be at the top of the file.

Don’t mix LF/CRLF

Or just don’t use Windows.

Use the correct certificate

Sometimes it helps to display the certificate you are trying to use to notice that it’s the wrong one. Display your certificate details like this:

openssl x509 -noout -text -in path/to/certificate/file.crt

Don’t forget to switch it on

Use tlsAuthWithCACert: true in the jsonData block, so that Grafana will evaluate your CA certificate.

Use the correct URL with https prefix

That should go without saying. Also, I should have found it sooner.

Wrap

I hope this will help … me! When I have to write the next Grafana datasource file.