All entities have an interface and an implementation. The methods on the interface are its effectors; the interface also defines its sensors.
Entities are created through the management context (rather than calling the
constructor directly). This returns a proxy for the entity rather than the real instance, which is important in a distributed management plane.
All entity implementations inherit from AbstractEntity
, often through one of the following:
SoftwareProcess
: if it's a software processVanillaJavaApp
: if it's a plain-old-java appJavaWebAppSoftwareProcess
: if it's a JVM-based web-appWhirrEntity
: if it's a service launched using WhirrDynamicGroup
: if it's a collection of other entitiesSoftware-based processes tend to use drivers to install and launch the remote processes onto locations which support that driver type. For example, AbstractSoftwareProcessSshDriver
is a common driver superclass, targetting SshMachineLocation
(a machine to which Brooklyn can ssh). The various SoftwareProcess
entities above (and some of the exemplars listed at the end of this page) have their own dedicated drivers.
Finally, there are a collection of traits, such as Resizable
, in the package brooklyn.entity.trait
. These provide common sensors and effectors on entities, supplied as interfaces. Choose one (or more) as appropriate.
So to get started:
@ImplementedBy(YourEntityImpl.class)
on your interface, where YourEntityImpl will be the class name for your entity implementation.SoftwareProcessDriver
). The naming convention is to have a suffix “Driver”.BasicEntityDriverFactory
.public Class getDriverInterface()
method in the entity implementation, to specify your driver interface.connectSensors()
of SoftwareProcessImpl
).. See the sensor feeds, such as HttpFeed
and JmxFeed
.Any JVM language can be used to write an entity. However use of pure Java is encouraged for entities in core brooklyn.
A few handy pointers will help make it easy to build your own entities. Check out some of the exemplar existing entities (note, some of the other entities use deprecated utilities and a deprecated class hierarchy; it is suggested to avoid these, looking at the ones below instead):
You might also find the following helpful: