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Posted to dev@brooklyn.apache.org by aledsage <gi...@git.apache.org> on 2017/03/09 00:01:15 UTC

[GitHub] brooklyn-server pull request #586: Conveniences for yaml

GitHub user aledsage opened a pull request:

    https://github.com/apache/brooklyn-server/pull/586

    Conveniences for yaml

    A few conveniences to make it easier to write my yaml blueprints! See individual commits for details.
    
    If anything in here looks controversial to you then please let me know, and I'll split things out into separate PRs.

You can merge this pull request into a Git repository by running:

    $ git pull https://github.com/aledsage/brooklyn-server conveniences-for-yaml

Alternatively you can review and apply these changes as the patch at:

    https://github.com/apache/brooklyn-server/pull/586.patch

To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:

    This closes #586
    
----
commit b2fd0e81761b30e963ffe12ae6108565d5f2ed1a
Author: Aled Sage <al...@gmail.com>
Date:   2017-03-08T20:37:41Z

    $brooklyn:object: support explicit \u201cdeferred\u201d
    
    YAML authors can specify \u201cdeferred\u201d, to force the object to only be
    constructed when the config is being retrieved.

commit 59624f52cbb2fc89cf5fcbba400a221db72c8028
Author: Aled Sage <al...@gmail.com>
Date:   2017-03-08T20:49:19Z

    TestHttpCall: support \u201cmaxAttempts\u201d config

commit acfcb91c311c177670629b54bd9d70a843e95611
Author: Aled Sage <al...@gmail.com>
Date:   2017-03-08T21:03:02Z

    Add typeCoercion (String->TimeZone; number->Date)

commit 7ddca12d489796bd916b1f8b70586b93dbdaabfa
Author: Aled Sage <al...@gmail.com>
Date:   2017-03-08T22:11:16Z

    $brooklyn:object - support coercing args

----


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[GitHub] brooklyn-server issue #586: Conveniences for yaml

Posted by aledsage <gi...@git.apache.org>.

Github user aledsage commented on the issue:

https://github.com/apache/brooklyn-server/pull/586

@tbouron Thanks. My use-case for `deferred` is a bit unusual! The "general" use-case is where you want to delay the creation/evaluation of the object until it's actually needed. And to have it being called every time it is evaluated, rather than evaluated only once and its value stored. One might want this for a number of reasons:

1. If evaluated statically, then that result is persisted (which may include confidential info). If `deferred`, then the persisted value will be the DSL.

2. There is a difference in behaviour for if a `$brooklyn:object` has an arg that is deferred (e.g. an arg that is `$brooklyn:config(...)`) versus if all the args can be statically evaluated: with the former, the value is the "deferred DSL"; with the latter, it is evaluated immediately. This allows one to force the two ways to behave the same.

My use-case is a bit sneaky (and one could argue misusing config, because the value changes each time you ask for it)! I am writing a yaml-based test for a service, and am using `org.apache.brooklyn.test.framework.TestHttpCall`. When constructing the URL, I need to include a timestamp (for "now") in the url query parameters. I therefore want some way to get the current timestamp at the time the url is being used (rather the time when the entity was constructed). For example:

```
type: org.apache.brooklyn.test.framework.TestHttpCall
brooklyn.config:
url:
$brooklyn:formatString:
- "%s/usage/?startTime=2016-01-01T00:00:00Z&endTime=%s"
- $brooklyn:component($brooklyn:config("targetId")).attributeWhenReady("main.uri")
- $brooklyn:formatString:
- "%sZ"
- $brooklyn:object:
type: org.apache.brooklyn.util.time.Time
factoryMethod.name: makeDateString
factoryMethod.args:
- $brooklyn:object:
deferred: true
type: java.lang.System
factoryMethod.name: currentTimeMillis
- yyyy-MM-dd'T'HH:mm:ss
- UTC
```

Without the `deferred: true`, the `endTime` is the time at which the entity was constructed. With the `deferred`, it is the time at which the entity's `start` effector is called (i.e. when it reads the `url` config value).

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[GitHub] brooklyn-server issue #586: Conveniences for yaml

Posted by aledsage <gi...@git.apache.org>.

Github user aledsage commented on the issue:

    https://github.com/apache/brooklyn-server/pull/586
  
    Thanks @tbouron - merging now.


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[GitHub] brooklyn-server issue #586: Conveniences for yaml

Posted by tbouron <gi...@git.apache.org>.

Github user tbouron commented on the issue:

    https://github.com/apache/brooklyn-server/pull/586
  
    @aledsage That makes sense, the example helped a lot to understand.
    
    LGTM then


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