[jira] [Commented] (BROOKLYN-458) Cluster can't use transformer to get "host.name" sensor of "cluster.first.entity"

["Aled Sage (JIRA)" <ji...@apache.org>]

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

Aled Sage commented on BROOKLYN-458:
------------------------------------

Below is a workaround for this (which relies on the {{triggerSensors}} on the transformer to recalculate it, and uses an {{Aggregator}} to ensure we populate a triggerSensor when the child gets its {{host.name}} set:
{noformat}
brooklyn.catalog:
  version: 0.2-SNAPSHOT
  items:

  - id: test-cluster
    name: test-cluster
    item:
      type: org.apache.brooklyn.entity.group.DynamicCluster

      memberSpec:
        $brooklyn:entitySpec:
          type: org.apache.brooklyn.entity.software.base.EmptySoftwareProcess
          name: "Node"
      
      brooklyn.enrichers:
        - type: org.apache.brooklyn.enricher.stock.Aggregator
          brooklyn.config:
            enricher.aggregating.fromMembers: true
            enricher.transformation.untyped: list
            enricher.sourceSensor: $brooklyn:sensor("host.name")
            enricher.targetSensor: $brooklyn:sensor("members.hostnames")
        - type: org.apache.brooklyn.enricher.stock.Transformer
          brooklyn.config:
            enricher.triggerSensors:
            - $brooklyn:sensor("cluster.first.entity")
            - $brooklyn:sensor("members.hostnames")
            enricher.targetSensor: $brooklyn:sensor("cluster_first_host")
            enricher.targetValue:
              $brooklyn:formatString:
              - "%s"
              - $brooklyn:entity($brooklyn:attributeWhenReady("cluster.first.entity")).attributeWhenReady("host.name")
{noformat}

> Cluster can't use transformer to get "host.name" sensor of "cluster.first.entity"
> ---------------------------------------------------------------------------------
>
>                 Key: BROOKLYN-458
>                 URL: https://issues.apache.org/jira/browse/BROOKLYN-458
>             Project: Brooklyn
>          Issue Type: Improvement
>            Reporter: Aled Sage
>
> Mike shared the blueprint below (which I've turned into a unit test, against 0.11.0-SNAPSHOT):
> {noformat}
>     @Test
>     public void testClusterGetsAttributeOfChild() throws Exception {
>         String yaml = Joiner.on("\n").join(
>                 "brooklyn.catalog:",
>                 "    version: 0.2-SNAPSHOT",
>                 "    items:",
>                 "    - id: test-cluster",
>                 "      name: test-cluster",
>                 "      item:",
>                 "        type: org.apache.brooklyn.entity.group.DynamicCluster",
>                 "        memberSpec:",
>                 "          $brooklyn:entitySpec:",
>                 "            type: org.apache.brooklyn.entity.software.base.EmptySoftwareProcess",
>                 "            name: \"Node\"",
>                 "        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\"",
>                 "                - $brooklyn:entity($brooklyn:attributeWhenReady(\"cluster.first.entity\")).attributeWhenReady(\"host.name\")");
>                         addCatalogItems(yaml);
>                 
>         String appYaml = Joiner.on("\n").join(
>                 "location: localhost",
>                 "services:",
>                 "- type: test-cluster");
>         
>         Entity app = createAndStartApplication(appYaml);
>         Entity cluster = Iterables.getOnlyElement(app.getChildren());
>         
>         EntityAsserts.assertAttributeEqualsEventually(app, Attributes.SERVICE_UP, true);
>         EntityAsserts.assertAttributeEqualsEventually(app, Attributes.SERVICE_STATE_ACTUAL, Lifecycle.RUNNING);
>         EntityAsserts.assertAttributeEventually(cluster, Sensors.newStringSensor("cluster_first_host"), StringPredicates.isNonBlank());
>     }
> {noformat}
> It fails because sensor {{cluster_first_host}} is never set on the cluster entity. This is because the targetValue evaluation is triggered whenever the sourceSensor changes. However, when {{clsuter.first.entity}} is set, that entity does not yet have a {{host.name}}. Therefore the {{attributeWhenReady}} is not yet available. (Under-the-covers, it discovers this by using {{getImmediately}}, and thus returns immediately without blocking).
> Mike tried to work around this by setting the {{producer}} for the transformer enricher, but that led to him hitting https://issues.apache.org/jira/browse/BROOKLYN-457.
> This is not really a bug (but could probably do with improvements in our docs to explain it!).
> We'd like a way to elegantly write this blueprint though (hence marking this as an "improvement").



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