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BUG#: 4898
TITLE: Add readme on statistics

DESCRIPTION: Adds new file to define status and use of statistics.

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README - Using the PEGASUS CIMSERVER STATISTICS

Author: Karl Schopmeyer <k.schopmeyer@opengroup.org> 

Date: 14 March 2006

The OpenPegasus CIMServer provides for gathering statistics on the CIM
operations executed by the server based on the CIM_CIMOMStatisticalData class
defined in the DMTF CIM_Interop model.

Statistics are gathered on all CIM Operations executed by the server when the
statistics are enabled.

When the statistics are enabled, the server gathers times and request and
response counts on each operation executed and maintains these counts and times
from the time the statistics were started.  For each operation executed the
following are gathered.

    * request size 
    * response size 
    * time spent in the server 
    * time spent in the providers

For each operation type defined (ex getclass, etc.) an instance of the
CIM_CIMOMStatisticalData class provides the following properties:

    * OperationType Enum (Value/Valuemap) defining the CIM operation
    type.

    * NumberOfOperations - Number of operations executed for this
    OperationType since the server was started or the statistics were
    turned on whichever occurred later.

    * CimomElapsedTime - Total time spent in the CIMServer for this
    operation in microseconds. This does not include time spent in the
    providers. That is defined by the ProviderResponseTime. This includes
    http processing, authentication, xml parsing and validation, routing,
    etc time that is common to all requests.

    * ProviderElapsedTime - Total time spent in the targeted providers for
    this operation. Note that for class and qualifier operations (ex.
    getclass) this is the time spent in the Pegasus Class repository.
    Further, if repository requests (ex getclass) are required in the
    server infrastructure to process an operation, that time is included as
    part of the server time, not provider time. The goal of providing this
    number is to measure times in the providers that are the support for
    the class(s) that represent the target of this operation.

    * RequestSize - Total size of the requests for this operation type in
    bytes.

    * ResponseSize - Total size of the responses for this operation type in
    bytes.

At any time, the statistics gathered by an OpenPegasus CIMServer can be
requested by a CIM client by enumerating the instances of the
CIM_CIMOMStatisticalData class from a client to the Pegasus server in the
PG/Interop namespace.  Note that there is no reset of statistics. They are
continuously gathered and accumulated and, the counts wrap when they exceed the
size of the property.

The client tool (cimperf) reports on averages for the times and byte sizes from
the totals provided by the CIM_CIMOMStatisticalData instances.

ENABLING AND DISABLING STATISTICS GATHERING

The statistics are normally disabled when the server environment is compiled.
The enabled/disabled status of statistics gathering is controlled through a
property in the CIM_ObjectManager instance (GatherStatisticalData)  maintained
by the server and persisted through the life of the instance repository.

The test client CLI includes a special set of operations (son and soff) that
directly set the GatherStatisticalData property true or false effectively
enabling/disabling statistics gathering.

ex. CLI son      - turns the statistics gathering on. CLI soff     
                 - turns the statistics gathering off.

Once statistics gathering is enabled or disabled this state is maintained
through cimserver or system restarts until either changed again or if the
repository is removed or the instance of the CIM_ObjectManager class is reset
or removed.

The cimserver does not maintain gathered statistics information if the erver is
stopped. Each startup of the server restarts all statistics counts from zero.

Disabling the statistics gathering also causes all of the statistics counts to
be reset to zero in the server.

CLIENT OPERATIONS STATISTICS REPORTING

In addition to the statistics reported through the CIM_CIMOMStatisticalData the
OpenPegasus server is capable of reporting operation execution time to the
client as part of each operation executed.  This function also is only active
when the statistics gathering capability has been enabled. The passage of this
information is defined in the DMTF CIMOperations specification (Version 1.2,
3.3.16. WBEMServerResponseTime).  Within the OpenPegasus Client API there is a
specific operation to request this information as part of each CIM operation.
This reports the total time spent in the CIMServer (server plus providers) for
the last operation executed. As an example, this is implemented in CLI.

LIMITATIONS

Currently no statistics are maintained on indications processed.  Provision is
made in the DMTF CIM_CIMOMStatisticalData class for gathering of indication
statistics but the exact form of the information is in question because this
differs from operations so this has not been implemented to date.

The client statistics test tool cimperf only prints out the current statistics
each time it is executed.  There are no client tools in the current pegasus
environment to maintain statistics history, show trends, etc.

If statistics are disabled, the statistics instances will still be output by
the cimserver  but will show zero for all values.

There are no automated tests today for the numbers accumulated by the
statistics gathering components.  The validity of the numbers produced in the
CIM_CIMOMStatisticalData instances has been verified by manual inspection
However, Currently there are no automated test to programatically verify the
statistics are correct.