[GitHub] brooklyn-server pull request #390: BROOKLYN-356: fix race in transformer by ...

[aledsage <gi...@git.apache.org>]

Github user aledsage commented on a diff in the pull request:

    https://github.com/apache/brooklyn-server/pull/390#discussion_r85903486
  
    --- Diff: camp/camp-brooklyn/src/main/java/org/apache/brooklyn/camp/brooklyn/spi/dsl/methods/DslComponent.java ---
    @@ -353,6 +386,33 @@ public DslSensorSupplier(DslComponent component, Object sensorIndicator) {
             }
     
             @Override
    +        public Maybe<Sensor<?>> getImmediately() {
    +            return getImmediately(sensorName, false);
    +        }
    +        
    +        protected Maybe<Sensor<?>> getImmediately(Object si, boolean resolved) {
    +            if (si instanceof Sensor) {
    +                return Maybe.<Sensor<?>>of((Sensor<?>)si);
    +            } else if (si instanceof String) {
    +                Entity targetEntity = component.get();
    +                Sensor<?> result = null;
    +                if (targetEntity!=null) {
    +                    result = targetEntity.getEntityType().getSensor((String)si);
    +                }
    +                if (result!=null) return Maybe.<Sensor<?>>of(result);
    +                return Maybe.<Sensor<?>>of(Sensors.newSensor(Object.class, (String)si));
    --- End diff --
    
    Not sure I follow. In `attributeWhenReady`, if we're given a sensor name then we will instantiate a new sensor object if it's not defined on the entity type; and then we look up the sensor's value (returning Maybe.absent if it's null). Here, we just want it to return the sensor object (rather than a sensor value) so we do the first half: instantiate a new sensor object if it's not defined on the entity type.
    
    This is consistent with the blocking `get()` method. We return `Maybe.absent()` if the `get()` method would have blocked, and otherwise we return the same value as `get()` would have returned.


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