How to: Use $$ (double-dollar sign) when your configuration needs a literal dollar sign.
services:
   foo:
      image: foo
      logging: *default-logging # alias(*): refer to 'default-logging' chunk 
```

#### Grafana Data Source

Add a TraceID derived field to extract the trace id and create a Tempo link from the trace id.

Grafana data source setting example:

![Data Source of Loki: Derived fields](./images/loki-derive-fields.png)

Grafana data source config example:

```yaml
name: Loki
type: loki
typeName: Loki
access: proxy
url: http://loki:3100
password: ''
user: ''
database: ''
basicAuth: false
isDefault: false
jsonData:
  derivedFields:
    - datasourceUid: tempo
      matcherRegex: (?:trace_id)=(\w+)
      matcherType: regex
      name: TraceID
      url: $${__value.raw}
      # Use $$ (double-dollar sign) when your configuration needs a literal dollar sign.
readOnly: false
editable: true
```