Sling Capabilities Module

This is a work in progress for a service that allows for creating Capabilities endpoints on a Sling instance: Resources that provide information on which services are available, version levels etc.

Capabilities are computed by Probes, simple classes that can use Health Checks, access external systems or do anything suitable to check what's available. Each Probe can return multiple values as String key/value pairs.

To define a Capabilities endpoint, create a Sling Resource with 1..N properties having names that end with the _probe suffix. The String value of each property is passed to all available ProbeBuilder services, and the first one that returns a Probe is used.

As an example, with the default Probes found in this module, creating a Resource such as

"caps": {
  "jcr:primaryType": "nt:unstructured",
  "foo_probe": "hc:The FOO cap:testing",
  "two_probe": "jvm:info",
  "3_probe": "hc:another HC:sometags",
  "sling:resourceType": "sling/capabilities"
}

At /tmp/caps for example, and requesting http://localhost:8080/tmp/caps.json produces the following output:

{
  "org.apache.sling.capabilities": {
    "The FOO cap": {
      "TODO": "would run HCs with tags testing"
    },
    "JvmProbe": {
      "java.specification.version": "1.8",
      "java.vm.version": "25.171-b11",
      "java.vm.vendor": "Oracle Corporation"
    },
    "another HC": {
      "TODO": "would run HCs with tags sometags"
    }
  }
}

This is not useful as is as the HC probes do not execute Health Checks yet - it's just meant to demonstrate how Probes are created and used.