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From "Graham Ashby" <>
Subject Re: How to express aggregator in yaml
Date Mon, 06 Mar 2017 16:10:34 GMT
Hi Sam
I've got an iterator in my template:

    <#list config['cm_host_port_list'] as cm_item>
      <crn:item xsi:type="xsd:anyURI">http://$

So, that's why I have an array.

So, I think I could do something with a Predicate, but I have no idea how 
I would wire this into the yaml.


From:   Sam Corbett <>
Date:   03/06/2017 10:36 AM
Subject:        Re: How to express aggregator in yaml

Hi Graham,

May I ask how you intend to use the values in your template?

If it would be sufficient to combine them into a single string you 
should use a `Joiner` enricher whose minimum size is the initial size of 
the cluster:

     cluster.initial.size: 4
   - type: org.apache.brooklyn.enricher.stock.Aggregator
       enricher.sourceSensor: mySensor
       enricher.targetSensor: aggregated
       enricher.aggregating.fromMembers: true
   - type: org.apache.brooklyn.enricher.stock.Joiner
       enricher.sourceSensor: aggregated
       enricher.targetSensor: joinedUp
       enricher.joiner.quote: false
       enricher.joiner.minimum: $brooklyn:config("cluster.initial.size")

In this example the value for `joinedUp` won't be published until the 
`aggregated` sensor contains four non-null values.

With this approach you wouldn't need to use a latch; in your other 
entity you'd assign the joiner's value to a config key:


And in your template write:


There is no equivalent of `enricher.joiner.minimum` for Aggregators so 
if this approach is unsuitable - perhaps you want to iterate over the 
values in your template - then it seems to be considerably more complex 
to achieve what you want. I've got a few ideas but will wait to hear 
whether the above is of any help before digging into them.


On 03/03/2017 19:12, Graham Ashby wrote:
> OK, I've got this problem:
> I have a list of hosts_ports that I've created in a cluster using an
> Aggregator.  So far so good.. .By using attributeWhenReady, it fills in
> when all the values are ready.
> Now in another part of my application, I want to use this in a template.
> The thing is, I want to wait until all the elements in the list are not
> null before I do the template.install.
> I've got a resources.install.latch, which seems to be the right latch to
> use.  However, it needs a boolean
> So my question is:  How can I write an Aggregator in yaml that will only
> be true if all the elements of the list are not null?
>   I'm sure it's possible, and I could do it if I was writing Java.  But
> there isn't a lot of documentation on how to do this.
> Thanks
> Graham Ashby

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