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From "Aled Sage (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (BROOKLYN-356) The sensor Transformer enricher fails to resolve its targetValue indeterministically.
Date Wed, 12 Oct 2016 11:40:20 GMT

    [ https://issues.apache.org/jira/browse/BROOKLYN-356?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15568484#comment-15568484
] 

Aled Sage commented on BROOKLYN-356:
------------------------------------

An easy way to reproduce this (when debugging) is to change {{DependentConfiguration.$WaitInTaskForAttributeReady.call()}}
to add a sleep at the start (e.g. {{Time.sleep(500);}}).

Then run {{TransformerEnricherWithDslTest.testTransformerResolvesResolvableValues()}}. It
fails first time because the transformer's attempt to retrieve the value times out after 200ms
(whereas the task will take a minimum of 500ms).

> The sensor Transformer enricher fails to resolve its targetValue indeterministically.
> -------------------------------------------------------------------------------------
>
>                 Key: BROOKLYN-356
>                 URL: https://issues.apache.org/jira/browse/BROOKLYN-356
>             Project: Brooklyn
>          Issue Type: Bug
>            Reporter: Svetoslav Neykov
>
> The sensor {{Transformer}} enricher fails to resolve its {{targetValue}} indeterministically,
especially so on loaded systems. This is especially problematic if sourceSensor/triggerSensors
change infrequently or do not change ever (when using default values).
> Bueprints using the {{Transformer}} behave perfectly fine during development and on test
setups, but will fail on production machines (i.e. under load).
> The code [doing the value resolving|https://github.com/apache/brooklyn-server/blob/b59e7463a9b337c2d0e7931cd420d5bac68d8549/core/src/main/java/org/apache/brooklyn/enricher/stock/Transformer.java#L90-L94]
tries to do so in a non-blocking fashion by spinning a thread to try to resolve and cancelling
it after a short while without guarantees it ever got scheduled to run. It's more likely to
fail when nesting DSLs, for example nesting several levels of {{$brooklyn:formatString}} and
ending with a {{$brooklyn:attributeWhenRready}}. It's a common pattern in moderately complex
blueprints. It needs to schedule a thread for each nesting level thus maximizing the chance
that the value will not be resolved in the allotted time even if resolvabe. This is especially
bad for sensors which don't get updated, for example {{PortAttributeSensorAndConfigKey} set
only when initializing the entity or any config values which are always resolvable.



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