Cloud Statistics Plugin

The plugin collects activities of other plugins and visualizes them as well as provides them to other plugins in form of an API.

Note that a provisioning plugin needs to explicitly integrate against this plugin in order to capture its statistics.

The statistics are presented on Manage Jenkins > Cloud Statistics.

Essentials

The plugin tracks the N most recent provisioning activities. One such activity covers the whole lifecycle from provisioning to agent deletion.
The activities have 4 hard-coded phases: provisioning, launching, operating and completed. Operation starts with first successful launch and ends with agent deletion (it is the only productive phase). The activity is completed once the agent is gone and the activity is effectively a history.
Each phase execution tracks start time and a list of attachments. The attachment is extensible and can be a mere piece of html, hyperlink or a model object with URL subspace. This is to attach and present any kind of information: logs, exceptions, etc.
Each attachment has a state: ok, warn or fail. The worst of all attached states is propagated to the phase execution and activity level. (If agent fails to launch, and exception will be attached explaining why the launch phase and thus the whole activity has failed).

In order for cloud-stats plugin to recognize provisioning activity to track, plugins are expected to do the following:

Make PlannedNode, Computer and Node implement TrackedItem. The interface provides a single method to connect all those using a dedicated Id instance. The instance holds some necessary data to connect it back to the cloud/template responsible for provisioning and works as a unique fingerprint identifying a single provisioning activity. Therefore, PlannedNode, Computer and Node are expected to provide the same instance of the Id. Note that there is a convenient abstract class TrackedPlannedNode that creates the Id so a plugin merely needs to pass it around.
In case there is a way to provision agents that does not go through Jenkins core (NodeProvisioner), plugins are expected to notify cloud-stats about such activity. This often happens when agents are provisioned manually in the Jenkins UI. Provided the agent gets attached to Jenkins, cloud-stats will track it just fine from launching phase on without any explicit notifications from a provisioning plugin.
Optionally, a plugin can attach any kind of information to any phase. cloud-stats is generally able to attach an exception in case of a failed launch or provisioning (with the exception mentioned above). Though a plugin may wants to attach logs, outputs, link to external services, etc.