Hi. For the project I am working on, we would like to use the CPU utilization as one of the metrics for scaling a cluster. The existing `MachineEntity` has a sensor feed that produces this data, along with uptime and memory usage information. The feed works on Linux VMs only, currently, as is uses SSH commands on the host to generate the values i.e. the `uptime` command, or the contents of files in `/proc/`.
I would like to propose moving the feed to `SoftwareProcess` so that it is available to all entities. It would be disabled normally, set by a `ConfigKey<Boolean>` flag. This would be named "metrics.machine.retrieve" to correspond to "metrics.usage.retrieve" which enables sensors in feeds that return application or process specific information. The `MachineEntity` would obviously have the default value set to "true", to maintain current behaviour. The only issue with this change is that the placement of the sensor feed feels slightly wrong. These are returning data about the _machine_ but the entity represents a _process_ on that machine, and there may in fact be multiple entities sharing a single machine, via `SameServerEntity`. The `MachineEntity` is used to represent a VM without any applications running on it, and would not normally be part of a blueprint, so these sensors are not normally accessible. There is some precedent for placing machine data on an entity, such as the `HOSTNAME` sensor, so I think the break in encapsulation is quite small. The PR containing the change is here: - https://github.com/apache/brooklyn-server/pull/204 I'd appreciate any comments on whether this is a useful change, as well as a review of the pull request... Thanks, Andrew. -- Andrew Kennedy ; Founder clocker.io project ; @grkvlt ; Cloudsoft
