Multi meter arithmetic transformer

[OpenStack Infra]

https://review.openstack.org/106302

Dear documentation bug triager. This bug was created here because we did not know how to map the project name "openstack/ceilometer" to a launchpad project name. This indicates that the notify_impact config needs tweaks. You can ask the OpenStack infra team (#openstack-infra on freenode) for help if you need to.

commit 971f9c85c1051d3291345152e4974f7beed23bf1
Author: Nejc Saje <email address hidden>
Date: Wed Jul 9 14:13:49 2014 +0200

    Multi meter arithmetic transformer

    New pipeline transformer that enables us to perform arithmetic calculations
    over one more meters and/or their metadata, for example:

        memory_util = 100 * memory.usage / memory .

    The calculation is limited to meters with the same interval.

    Example configuration:

        - name: "arithmetic"
          parameters:
            target:
              name: "memory_util"
              unit: "%"
              type: "gauge"
              expr: "100 * $(memory.usage) / $(memory)"

    To demonstrate the use of metadata, here is the implementation of
    a silly metric that shows average CPU time per core::

        - name: "arithmetic"
          parameters:
            target:
              name: "avg_cpu_per_core"
              unit: "ns"
              type: "cumulative"
              expr: "$(cpu) / ($(cpu).resource_metadata.cpu_number or 1)"

    Expression evaluation gracefully handles NaNs and exceptions. In such
    a case it does not create a new sample but only logs a warning.

    DocImpact: add documentation about using this new transformer
    Implements: blueprint arithmetic-transformer
    Change-Id: I1b637e5b1d1bb15ed3c3d7ec758d2a684eaccf21

[Ildiko Vancsa (ildiko-vancsa)]

Docco is added into the Administrator Guide: http://docs.openstack.org/admin-guide-cloud/content/section_telemetry-pipeline-transformers.html