To support multi-tenancy we are using multiple SiftingAppenders. Some contain log appenders, but one contains a DBAppender. To get the appenders the correct database connection information we need to use nested variables/options where the options are evaluated from the inside-out:

<url>${${tenantID}.jdbc.url}</url>
<user>${${tenantID}.db.user}</user>
<password>${${tenantID}.db.password</password>

See also https://github.com/qos-ch/logback/pull/56