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readme.cmpi
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//%LICENSE////////////////////////////////////////////////////////////////
//
// Licensed to The Open Group (TOG) under one or more contributor license
// agreements. Refer to the OpenPegasusNOTICE.txt file distributed with
// this work for additional information regarding copyright ownership.
// Each contributor licenses this file to you under the OpenPegasus Open
// Source License; you may not use this file except in compliance with the
// License.
//
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the "Software"),
// to deal in the Software without restriction, including without limitation
// the rights to use, copy, modify, merge, publish, distribute, sublicense,
// and/or sell copies of the Software, and to permit persons to whom the
// Software is furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included
// in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
// IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
// CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
// TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
// SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//
//////////////////////////////////////////////////////////////////////////
Common Management Programming Interface (CMPI) Providers in a nutshell
============================
Aug 1st, 2005
Pegasus 2.5 *NEWS*
------------------
The CMPI macro header files (cmpimacs.h) shipped is OpenPegasus specific. This
will change once OpenGroup releases a specification with the macro definitions.
The CMPI Function Table (cmpift.h) file and CMPI Data Types (cmpidt.h) file are
composed from the CMPI v1.0 specification + Technical Corrigenda and are
binary compatible with the "historical implementations" and the 1.0 specification
augmented with the Technical Corrigenda.
Build CMPI from sources
-----------------------
The Common Manageability Programming Interface (CMPI) has been integrated into
Pegasus as a pluggable provider manager.
CMPI is by default enabled on Linux. For other platforms it must be enabled
during Pegasus build.
For CMPI enablement, set the following environment variables prior to make:
PEGASUS_ENABLE_CMPI_PROVIDER_MANAGER=1
Using CMPI
----------
If you plan to write your own CMPI providers you are kindly referred to the
WBEMSource homepage where the draft specification document for CMPI resides.
You can find at http://www.wbemsource.org/doc.tpl?CALLER=index.tpl&gdid=3712 .
If you are looking for samples you should have a look at the SBLIM project.
The packages prefixed by the string sblim-cmpi contain CMPI providers for
various classes. See http://www-124.ibm.com/developerworks/projects/sblim .
Using CMPI with threads
-----------------------
CMPI provides API functions for low-level thread, mutex and conditional constructs.
Hence you can compile your provider without needing to link to pthread or other
threading library.
However, the developer is responsible for memory management of these constructs and
as well of exiting the threads before the cleanup function is exited. If this is not
done, the thread will be forcefully terminated. This can have the nasty consequence of
hanging CIMServer, or bringing down the CIMServer, or just the Out-of-Process Provider
Agent if you run OpenPegasus with 'run-as-requester' configuration flag turned on.
Please refer to the Admin Guide or the readme files for more details about this flag.
Using CQL with CMPI
-------------------
To use CQL support for indications and exec query you will have to use
the Pegasus/Provider/CMPI/cmpi_cql.h header file with one new function.
You also you need to define PEGASUS_USE_EXPERIMENTAL in your
code to take advantage of these CQL utility functions. The reason is that
the CMPI standard 1.0 is unclear on one thing:
- CMNewSelectExp. One of arguments passed is a 'projection' array. The
spec does not explain exactly what in such array. Implementation of
CMPI that also implemented WQL put a string representation of the
properties, as "SystemName", "Hostname", etc. But that is not neccesarily
the case with CQL, where you can have chained identifiers such as
"CIM_OperatingSystem::SystemName". In other words, the CMPI standard
needs to clarify this and to make the existing providers backward
supported, this utility function - CMPI_CQL_NewSelectExp is provided
until the CMPI standard comes up with a conclusion on this.
When the CMPI provides a resolution on these issues, this utility
interface will be gone and unsupported.
Questions and Answers:
Q1: Is the CMPI Specification really ambiguous or does it
just not support CQL? If it's ambiguous should it be fixed
before it goes final?
A1:. Page 96 of the CMPI review spec states (line 2899-2901): The *projection output argument is
a pointer to a CMPIArray structure of CMPIString entries containing projection specification.
It shall be set to NULL if no projection is defined.. To clarify any ambigiuity, an e-mail to the
CMPI review group was sent, which would add the following: The projection specification is query
language specific. Hence the entries format of the projection output array CMPIString might be
different depending on the query language. Be sure to check the lang argument for the query language your
provider will support. . To guard the provider from DMTF's CQL possible ways it can be represented in
a string format, and since the CQL is experimental, the CMNewSelectExp will NOT support CQL.
The CMPI_CQL_NewSelect will support both CQL and WQL.
AQ:What happens if an existing Provider is passed a CQL
statement and issues a newSelectExp call? Does it return
an error?
A2: The error code CMPI_RC_ERR_QUERY_LANGUAGE_NOT_SUPPORTED would be set.
Q3: Both CMNewSelectExp and CMPI_CQL_NewSelectExp return a
CMPISelectExp. Is there anyway to determine whether the
CMPISelectExp represents a CQL or WQL expression?
A3:Not from the scope of the CMPISelectExp structure. Please note that the routine
that would exercise the CMPISelectExp has a char *lang passed in as argument.
This char *lang* can be used to easily determine what query language is used.
Registering CMPI providers with Pegasus
---------------------------------------
Once you have a CMPI provider library you want to register it with Pegasus.
How? Well it's almost the same as for C++ providers. The only difference is
that the Provider.Interface property must be set to "CMPI".
Here's an excerpt from the SBLIM Linux Computer System provider registration
// ===================================================================
// Linux_ComputerSystem
// ===================================================================
instance of PG_ProviderModule
{
Name = "OSBase_ComputerSystemProviderModule";
//The library name on disk
Location = "cmpiOSBase_ComputerSystemProvider";
Vendor = "SBLIM";
Version = "1.2.2";
InterfaceType = "CMPI";
InterfaceVersion = "0.86.0";
};
instance of PG_Provider
{
//The provider module as defined in PG_ProviderModule
ProviderModuleName = "OSBase_ComputerSystemProviderModule";
// The provider name as referenced in the code
Name = "OSBase_ComputerSystemProvider";
};
instance of PG_ProviderCapabilities
{
//The provider module as defined in PG_ProviderModule
ProviderModuleName = "OSBase_ComputerSystemProviderModule";
//The provider name as defined in PG_Provider
ProviderName = "OSBase_ComputerSystemProvider";
CapabilityID = "1";
//Name of the CIM class as defined in the mof
ClassName = "Linux_ComputerSystem";
Namespaces = {"root/cimv2"};
ProviderType = { 2,5 }; // Instance, Method
SupportedProperties = NULL; // All properties
SupportedMethods = NULL; // All methods
};