Attributes with entity as value; accessing its attributes

[Richard Downer]

Hi all,

In my blueprint, I have a group of MariaDBs, and I want to get the host.name
of one entity in the group. The group exposes a sensor
`cluster.first.entity`, so I want to get that entity, and then get its
sensor `host.name`.

Here's a fragment of my blueprint where I try to do this (reduced to as
simple a blueprint as will demonstrate the problem):

  - type:
'org.apache.brooklyn.entity.software.base.VanillaSoftwareProcess:4.5.0'
    location: localhost
    brooklyn.config:
      example: $brooklyn:formatString("mysql://%s",
component("group").attributeWhenReady("cluster.first.entity").attributeWhenReady("
host.name"))
      install.command: echo $EXAMPLE
      shell.env:
        EXAMPLE: '$brooklyn:config("example")'

So I would expect this to echo out a valid hostname, if I go into the
Activity view and find the SSH task stdout.

What I actually get is something like this:

mysql://$brooklyn:entity(org.apache.brooklyn.camp.brooklyn.spi.dsl.methods.BrooklynDslCommon$DslFacades$EntitySupplier@30c91bfc
).attributeWhenReady("host.name")

Is this kind of thing supposed to work? Am I doing something wrong?

Thanks
Richard.