Re: Trouble with YAML Transformer

Thu, 23 Mar 2017 06:15:33 -0700 

Hi Graham,
I think that is non-deterministic: it failed approx 50% of the time in my simple unit test. 


As described in BROOKLYN-458, the problem is that it will evaluate the 
expression when the sensor "cluster.first.entity" is set. It will 
immediately look up the "host.name" of that entity. If that sensor is 
aleady set, then great. If it is not yet set, it will return immediately 
without setting "cluster_first_host". Nothing will subsequently trigger 
the transformer again (because "clustere.first.entity" does not change), 
until Brooklyn is restarted or the first.entity is replaced.



There is a workaround suggested in BROOKLYN-458 that uses 
"triggerSensors" (and an extra aggregated sensor!) to ensure that the 
value is re-evaluated when the entity gets its host.name.


Aled


p.s. if you deploy this to a location where it takes a while for 
"host.name" to become available and thus populated (e.g. where it 
requires provisioning VMs), then it's much more likely to fail. If that 
is working for you consistently then let me know as I'd be interested to 
find out why!



On 23/03/2017 13:07, Graham Ashby wrote:

Thanks all for all your help.

For the record, what finally worked is:

       - type: org.apache.brooklyn.enricher.stock.Transformer
         brooklyn.config:
           enricher.sourceSensor: $brooklyn:sensor("cluster.first.entity")
           enricher.targetSensor: $brooklyn:sensor("cluster_first_host")
           enricher.targetValue:
$brooklyn:entity($brooklyn:attributeWhenReady("cluster.first.entity")).attributeWhenReady("host.name")

Graham



From:   Aled Sage <[email protected]>
To:     [email protected]
Date:   03/23/2017 07:47 AM
Subject:        Re: Trouble with YAML Transformer



Hi Graham, Mike, all,

Graham: for why your transformer isn't populating the sensor value, see
the explanation I've written up at
https://issues.apache.org/jira/browse/BROOKLYN-458.

For a workaround, see my first comment on that jira issue:


     
https://issues.apache.org/jira/browse/BROOKLYN-458?focusedCommentId=15938141&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-15938141




---
For the single-arg `$brooklyn:sensor(...)`...

`$brooklyn:sensor("cluster.first.entity")` returns a new
`AttributeSensor<Object>` instance, with name "cluster.first.entity". It
doesn't look up the actual value of the sensor on the entity.

What it means by "the given sensor on the current entity if found" is
that: if the entity declares a strongly typed sensor with exactly that
name (e.g. that also has a description and/or a type that is not
Object), then it will be the entity's own sensor instance returned
rather than constructing a new instance.

---
Mike: as discussed with you offline, the error for:

  $brooklyn:sensor("cluster.first.entity").attributeWhenReady("host.name")

is reported at https://issues.apache.org/jira/browse/BROOKLYN-454, along
with a workaround.

The workaround is to use:


  
$brooklyn:entity($brooklyn:sensor("cluster.first.entity")).attributeWhenReady("host.name")


---
For the record, Mike also hit
https://issues.apache.org/jira/browse/BROOKLYN-457 while exploring
possible solutions for Graham's use-case.

---
Mike, could you please see what Brooklyn docs we can improve to make
this clearer, and easier to use/understand? Also what should we improve
to make investigating/debugging such problems easier?

Aled


On 22/03/2017 20:52, Graham Ashby wrote:

And if I try:

            enricher.targetValue:
$brooklyn:sensor("cluster.first.entity").attributeWhenReady("host.name")

I get the error:

Error evaluating node (rethrowing)


'$brooklyn:sensor("cluster.first.entity").attributeWhenReady("host.name")':

java.lang.IllegalArgumentException: No such function

'attributeWhenReady'

on sensor("cluster.first.entity")



From:   Mike Zaccardo <[email protected]>
To:     [email protected]
Date:   03/22/2017 04:31 PM
Subject:        Re: Trouble with YAML Transformer



  From the DSL spec [


https://docs.cloudsoft.io/blueprints/syntax-yaml-reference.html#dsl-commands


]:

* $brooklyn:sensor("sensor.name") returns the given sensor on the

current

entity if found, or an untyped (Object) sensor;

* $brooklyn:sensor("com.acme.brooklyn.ContainingEntityClass",
"sensor.name")
returns the strongly typed sensor defined in the given class

Based on that, it seemed to me that the first, single-argument value

would

actually return the value of the sensor (the "object"), not the sensor
construct itself (the "class").  However, I tried updating your code and
ended up with an empty-valued sensor.

        brooklyn.enrichers:
          - type: org.apache.brooklyn.enricher.stock.Transformer
            brooklyn.config:
              enricher.sourceSensor:
$brooklyn:sensor("cluster.first.entity")
              enricher.targetSensor:

$brooklyn:sensor("cluster_first_host")

              enricher.targetValue:
                $brooklyn:formatString:
                - "%s"
                -
$brooklyn:sensor("cluster.first.entity").attributeWhenReady("host.name")

I'd like to kick the question to the rest of the community -- why does
that
^ end up with an empty value? It should default to searching the current
entity, which is a `DynamicCluster`, which has a `cluster.first.entity`.

-Mike

On Wed, Mar 22, 2017 at 12:52 PM Graham Ashby <[email protected]>
wrote:

OK, Stupid mistake.
So, when I changed it to colon, I got the error:
2017-03-22 15:41:43,612 WARN  o.a.b.c.b.s.d.BrooklynDslInterpreter
[brooklyn-jetty-server-8081-qtp434786215-42]: Error evaluating node
(rethrowing) '$brooklyn:sensor("org.apache.brooklyn.api.entity.Entity",
"cluster.first.entity").attributeWhenReady("host.name")':
org.apache.brooklyn.util.exceptions.PropagatedRuntimeException: Sensor
cluster.first.entity not found on class
org.apache.brooklyn.api.entity.Entity

So I changed the Cast:

            enricher.targetValue:
$brooklyn:sensor("org.apache.brooklyn.entity.group.AbstractGroup",
"cluster.first.entity").attributeWhenReady("host.name")

Now I get:

2017-03-22 15:43:50,909 WARN  o.a.b.c.b.s.d.BrooklynDslInterpreter
[brooklyn-jetty-server-8081-qtp434786215-2217]: Error evaluating node
(rethrowing)
'$brooklyn:sensor("org.apache.brooklyn.entity.group.AbstractGroup",
"cluster.first.entity").attributeWhenReady("host.name")':
java.lang.IllegalArgumentException: Not permitted to invoke function on
'class org.apache.brooklyn.core.sensor.BasicAttributeSensor' (outside
allowed package scope)

Thanks
G



From:   Mike Zaccardo <[email protected]>
To:     Brooklyn dev <[email protected]>
Date:   03/22/2017 03:30 PM
Subject:        Re: Trouble with YAML Transformer



Hi Graham,

In your `enricher.targetValue` -- `$brooklyn.sensor` should be
`$brooklyn:sensor`
(the dot replaced by a colon).

If that does not solve it, try providing the `enricher.targetValue` with
string, like so:

      brooklyn.enrichers:
        - type: org.apache.brooklyn.enricher.stock.Transformer
          brooklyn.config:
            enricher.sourceSensor:

$brooklyn:sensor("cluster.first.entity")

            enricher.targetSensor: $brooklyn:sensor("cluster_first_host")
            enricher.targetValue:
              $brooklyn:formatString:
              - "%s"
              -
$brooklyn:sensor("org.apache.brooklyn.api.entity.Entity",
"cluster.first.entity").attributeWhenReady("
host.name")

I hope this helps.

Cheers,
Mike

On Wed, Mar 22, 2017 at 12:10 PM Graham Ashby <[email protected]>
wrote:

What I want is an attribute that I can include in a template.
I'm trying to get the host.name of the first entity in the cluster, so
what I've got is:

      brooklyn.enrichers:
        - type: org.apache.brooklyn.enricher.stock.Transformer
          brooklyn.config:
            enricher.sourceSensor:

$brooklyn:sensor("cluster.first.entity")

            enricher.targetSensor: $brooklyn:sensor("cluster_first_host")
            enricher.targetValue:
$brooklyn.sensor("org.apache.brooklyn.api.entity.Entity",
"cluster.first.entity").attributeWhenReady("host.name")

But I get the literal value
"$brooklyn.sensor("org.apache.brooklyn.api.entity.Entity",
"cluster.first.entity").attributeWhenReady("host.name")"

So, what am I doing wrong?

Thanks
Graham

--

Mike Zaccardo

Senior Software Engineer

Skype: mike.cloudsoft

Twitter: @ItsMeMikeZ <https://twitter.com/ItsMeMikeZ> LinkedIn:
linkedin.com/in/mike-zaccardo
<https://www.linkedin.com/in/mike-zaccardo-aa3ab812>

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