Hi.
Currently the only initializer for new effectors that can be used in a YAML
blueprint is the SshCommandEffector, which creates an effector that can
execute an SSH command on an entity. This is useful, but it would be good
to have more flexibility, including access to some of the Brooklyn
internals. So, I had a look at the JSR-223 scripting extensions to Java,
and built a new initializer that can add an effector whose body is a piece
of code defined in the blueprint. This code can be in any language
supported by the running JVM. Currently only JavaScript is available by
default, but my implementation also adds Python 2.7 via the Jython project.
As an example, here is an entity that has a JavaScript effector that takes
two arguments, a name and a count, and returns the name repeated multiple
times. A real effector would actually do something useful, obviously:
services:
- type: org.apache.brooklyn.entity.stock.BasicStartable
brooklyn.initializers:
- type: org.apache.brooklyn.core.effector.script.ScriptEffector
brooklyn.config:
name: javascript
description: |
An effector implemented in JavaScript
parameters:
name:
type: java.lang.String
description: "Your name"
count:
type: java.lang.Integer
description: "Number of repetitions"
script.language: "JavaScript"
script.return.var: "data"
script.return.type: java.lang.String
script.content: |
var data = "";
var n = 0;
while (n < count) {
data += name;
n++;
}
The return value is coerced to script.return.type using TypeCoercions and
can be either the content of a variable specified in script.return.var or
the default return value of the code, which is often the value of the last
expression, if the language supports this. The script content can also be
provided as a URL pointing to a file, instead of inline.
I am also trying to inject variables into the execution context of the
script, so that the code has access to the current task, the calling entity
and its management context and other useful Brooklyn objects.
I have created a pull request with the initial code, so that people can see
the current status:
- https://github.com/apache/brooklyn-server/pull/153
This is still work in progress, so further suggestions welcome...
Cheers,
Andrew.
--
Andrew Kennedy ; Founder clocker.io project ; @grkvlt ; Cloudsoft
