Github user tbouron commented on a diff in the pull request:
https://github.com/apache/brooklyn-docs/pull/194#discussion_r120547131
--- Diff: guide/blueprints/effectors.md ---
@@ -0,0 +1,167 @@
+---
+title: Effectors
+layout: website-normal
+---
+
+Effectors perform an operation of some kind, carried out by a Brooklyn
Entity.
+They can be manually invoked or triggered by a Policy.
+
+Common uses of a effector include the following:
+
+* perform a command on a remote machine,
+* collect data and publish them to sensors.
+
+Entities have default effectors, the lifecycle management effectors like
``start``, ``stop``, ``restart``, and clearly more ``Effectors`` can be
attached to them.
+
+Off-the-Shelf Effectors
+----------------------
+
+Effectors are highly reusable as their inputs, thresholds and targets are
customizable.
+
+### SSHCommandEffector
+
+An ```Effector``` to invoke a command on a node accessible via SSH.
+
+It allows to execute a ```command``` in a specific ```execution
director``` (executionDir) by using a custom ```shell environment` (shellEnv).
+By default, the specified command will be executed on the entity where the
effector is attached or on all *children* or all *members* (if it is a group)
by configuring ```executionTarget```.
+
+Here a simple example of an ```SshCommandEffector``` definition:
+
+{% highlight yaml %}
+ brooklyn.initializers:
+ - type: org.apache.brooklyn.core.effector.ssh.SshCommandEffector
+ brooklyn.config:
+ name: sayHiNetcat
+ description: Echo a small hello string to the netcat entity
+ command: |
+ echo $message | nc $TARGET_HOSTNAME 4321
+ parameters:
+ message:
+ description: The string to pass to netcat
+ defaultValue: hi netcat
+{% endhighlight %}
+
+See
[```here```](https://brooklyn.apache.org/v/latest/misc/javadoc/org/apache/brooklyn/core/effector/ssh/SshCommandEffector.html)
for more details.
+
+### HTTPCommandEffector
+
+An ```Effector``` to invoke REST endpoints.
+
+It allows to specify the URI, the HTTP verb, credentials for
authentication and HTTP headers.
+
+It deals with some ```HttpHeaders.CONTENT_TYPE``` namely
*application/json* (as default) and *application/x-www-form-urlencoded*.
+In the latter case, a map payload will be ```URLEncoded``` in a single
string.
+
+With optional ```JSON_PATH``` configuration key, the effector will extract
a section of the json response.
+
+Using ```JSON_PATHS_AND_SENSORS``` configuration key, it is possible to
extract one or more values from a json response, and publish them in sensors.
+
+{% highlight yaml %}
+brooklyn.initializers:
+- type: org.apache.brooklyn.core.effector.http.HttpCommandEffector
+ brooklyn.config:
+ name: request-access-token
+ description: Request an access token for the Azure API
+ uri:
+ $brooklyn:formatString:
+ - "https://login.windows.net/%s/oauth2/token";
+ - $brooklyn:config("tenant.id")
+ httpVerb: POST
+ httpPayload:
+ resource: https://management.core.windows.net/
+ client_id: $brooklyn:config("application.id")
+ grant_type: client_credentials
+ client_secret: $brooklyn:config("application.secret")
+ jsonPathAndSensors:
+ $.access_token: access.token
+ headers:
+ Content-Type: "application/x-www-form-urlencoded"
+{% endhighlight %}
+
+See
[```here```](https://brooklyn.apache.org/v/latest/misc/javadoc/org/apache/brooklyn/core/effector/http/HttpCommandEffector.html)
for more details.
+
+### AddChildrenEffector
+
+An ```Effector``` to add a child blueprint to an entity.
+
+{% highlight yaml %}
+brooklyn.initializers:
+- type: org.apache.brooklyn.core.effector.AddChildrenEffector
+ brooklyn.config:
+ name: add_tomcat
+ blueprint_yaml: |
+ name: sample
+ description: Tomcat sample JSP and servlet application.
+ origin: http://www.oracle.com/nCAMP/Hand
+ services:
+ -
+ type: io.camp.mock:AppServer
+ name: Hello WAR
+ wars:
+ /: hello.war
+ controller.spec:
+ port: 80
+
+ brooklyn.catalog:
+ name: catalog-name
+ type: io.camp.mock.MyApplication
+ version: 0.9
+ libraries:
+ - name:
org.apache.brooklyn.test.resources.osgi.brooklyn-test-osgi-entities
+ version: 0.1.0
+ url: classpath:/brooklyn/osgi/brooklyn-test-osgi-entities.jar
+ auto_start: true
+{% endhighlight %}
+
+One of the config keys ```BLUEPRINT_YAML``` (containing a YAML blueprint
(map or string)) or ```BLUEPRINT_TYPE``` (containing a string referring to a
catalog type) should be supplied, but not both.
+
+See
[```here```](https://brooklyn.apache.org/v/latest/misc/javadoc/org/apache/brooklyn/core/effector/AddChildrenEffector.html)
for more details.
+
+Writing an Effector
+-------------------
+
+### Your First Effector
+
+Effectors generally perform actions on entities.
+Each effector instance is associated with an entity,
+and at runtime it will typically exectute an operation, collect the result
and, potentially, publish it as sensor on that entity, performing some
computation.
+
+Writing a effector is straightforward.
+Simply extend
[``AddEffector``](https://brooklyn.apache.org/v/latest/misc/javadoc/org/apache/brooklyn/core/effector/AddEffector.html),
+providing an implementation for ``newEffectorBuilder`` and adding a
constructor that consumes the builder or override an existing effector.
+
+{% highlight java %}
+
+ public MyEffector(ConfigBag params) {
+ super(newEffectorBuilder(params).build());
+}
+
+public static EffectorBuilder<String> newEffectorBuilder(ConfigBag params)
{
+ EffectorBuilder<String> eff =
AddEffector.newEffectorBuilder(String.class, params);
+ eff.impl(new Body(eff.buildAbstract(), params));
+ return eff;
+}
+{% endhighlight %}
+
+and supply an ```EffectorBody``` similar to:
+
+{% highlight java %}
+
+protected static class Body extends EffectorBody<String> {
+ ...
+
+ @Override
+ public String call(final ConfigBag params) {
+ ...
+ }
+}
+{% endhighlight %}
+
+### Best Practice
+
+The following recommendations should be considered when designing policies:
+
+#### Policies should be small and composable
--- End diff --
s/Policies/Effectors
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