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From "Aled Sage (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (BROOKLYN-267) brooklyn.parameter default value not picked up via inherited config
Date Mon, 16 May 2016 14:01:12 GMT

    [ https://issues.apache.org/jira/browse/BROOKLYN-267?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15284613#comment-15284613
] 

Aled Sage commented on BROOKLYN-267:
------------------------------------

Added test that demonstrates this in https://github.com/apache/brooklyn-server/pull/139

> brooklyn.parameter default value not picked up via inherited config
> -------------------------------------------------------------------
>
>                 Key: BROOKLYN-267
>                 URL: https://issues.apache.org/jira/browse/BROOKLYN-267
>             Project: Brooklyn
>          Issue Type: Bug
>    Affects Versions: 0.9.0
>            Reporter: Aled Sage
>            Priority: Minor
>
> When adding the item below to the catalog, I get surprising behaviour when retrieving
the "test.myconf" parameter at different levels.
> When inside a child entity, trying to do {{$brooklyn:config("test.myconf")}}, it returns
null. But if I do {{$brooklyn:root().config("test.myconf")}} then it works as I'd expect (i.e.
I get the default value).
> {noformat}
> brooklyn.catalog:
>   id: my-example
>   version: 1.2.3
>   item:
>     brooklyn.parameters:
>     - name: test.myconf
>       type:  string
>       default: myval
>     services:
>     - type: org.apache.brooklyn.entity.stock.BasicApplication
>       brooklyn.config:
>         myconf2: $brooklyn:config("test.myconf")
>         myconf2.from.root: $brooklyn:root().config("test.myconf")
>       brooklyn.children:
>       - type: org.apache.brooklyn.entity.stock.BasicEntity
>         brooklyn.config:
>           myconf3: $brooklyn:config("test.myconf")
>           myconf3.from.root: $brooklyn:root().config("test.myconf")
> {noformat}
> The reason, I believe, is that {{$brooklyn:config("test.myconf")}} on the child will
lookup the child's explicitly defined config keys and not find any. It will therefore create
a new {{ConfigKey}} object with no default value. It looks up its own config and then the
inherited config, but sees no explicit value set. So it falls back to the configKey.defaultValue.
But because we synthesised a new config key object, we don't get the default value that was
defined in the {{brooklyn.parameters}} section.
> ---
> Overall, I think it's best if:
> * our exemplar blueprints use things like {{$brooklyn:root().config("test.myconf")}}
(because that has a very clear meaning);
> * and we change our config key lookup so that we only synthesis a config key object if
none of the current entity or any of its ancestors in the parent hierarchy has a matching
config key.
> For point (2), this could lead to surprising behaviour in edge cases where a hierarchy
of entities includes something pulled in from another entity type in the catalog, and where
that entity type happens to declare a config key by the same name with a default value. At
that point, the user looking at their own yaml file might be surprised that it didn't pick
up the default value they are looking at in front of them.



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