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version 1.5, 2004/10/13 14:45:26
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version 1.7, 2005/08/04 19:11:51
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| CMPI Providers in a nutshell |
Common Management Programming Interface (CMPI) Providers in a nutshell |
| ============================ | ============================ |
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| Viktor Mihajlovski <mihajlov@de.ibm.com> |
Aug 1st, 2005 |
| Nov 14th 2003 |
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| Pegasus 2.4 *NEWS* |
Pegasus 2.5 *NEWS* |
| ------------------ | ------------------ |
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| The CMPI header files are being standardized and will be (possibly by the |
The CMPI macro header files (cmpimacs.h) shipped is OpenPegasus specific. This |
| time you read this) frozen. However, since the OpenPegasus 2.4 release is |
will change once OpenGroup releases a specification with the macro definitions. |
| anticipated prior to the anticipated freezing of the CMPI standard, |
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| the OpenPegasus 2.4 release will not provide the CMPI header files as |
The CMPI Function Table (cmpift.h) file and CMPI Data Types (cmpidt.h) file are |
| part of the OpenPegasus 2.4 SDK. |
composed from the CMPI v1.0 specification + Technical Corrigenda and are |
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binary compatible with the "historical implementations" and the 1.0 specification |
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augmented with the Technical Corrigenda. |
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| They can be found within CVS and the source tarball. Visit |
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| http://cvs.opengroup.org/cgi-bin/viewcvs.cgi/pegasus/src/Pegasus/Provider/CMPI/ to view the CMPI header files. |
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| Build CMPI from sources | Build CMPI from sources |
| ----------------------- | ----------------------- |
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| The Common Manageability Programming Interface (CMPI) has been integrated into | The Common Manageability Programming Interface (CMPI) has been integrated into |
| Pegasus as a pluggable provider manager. | Pegasus as a pluggable provider manager. |
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| CMPI must be enabled during Pegasus build. |
CMPI is by default enabled on Linux. For other platforms it must be enabled |
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during Pegasus build. |
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| For CMPI enablement, set the following environment variables prior to make: | For CMPI enablement, set the following environment variables prior to make: |
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| PEGASUS_ENABLE_CMPI_PROVIDER_MANAGER=1 | PEGASUS_ENABLE_CMPI_PROVIDER_MANAGER=1 |
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| The packages prefixed by the string sblim-cmpi contain CMPI providers for | The packages prefixed by the string sblim-cmpi contain CMPI providers for |
| various classes. See http://www-124.ibm.com/developerworks/projects/sblim . | various classes. See http://www-124.ibm.com/developerworks/projects/sblim . |
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Using CMPI with threads |
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----------------------- |
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CMPI provides API functions for low-level thread, mutex and conditional constructs. |
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Hence you can compile your provider without needing to link to pthread or other |
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threading library. |
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However, the developer is responsible for memory management of these constructs and |
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as well of exiting the threads before the cleanup function is exited. If this is not |
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done, the thread will be forcefully terminated. This can have the nasty consequence of |
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hanging CIMServer, or bringing down the CIMServer, or just the Out-of-Process Provider |
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Agent if you run OpenPegasus with 'run-as-requester' configuration flag turned on. |
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Please refer to the Admin Guide or the readme files for more details about this flag. |
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Using CQL with CMPI |
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------------------- |
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To use CQL support for indications and exec query you will have to use |
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the Pegasus/Provider/CMPI/cmpi_cql.h header file with one new function. |
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You also you need to define PEGASUS_USE_EXPERIMENTAL in your |
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code to take advantage of these CQL utility functions. The reason is that |
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the CMPI standard 1.0 is unclear on one thing: |
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- CMNewSelectExp. One of arguments passed is a 'projection' array. The |
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spec does not explain exactly what in such array. Implementation of |
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CMPI that also implemented WQL put a string representation of the |
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properties, as "SystemName", "Hostname", etc. But that is not neccesarily |
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the case with CQL, where you can have chained identifiers such as |
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"CIM_OperatingSystem::SystemName". In other words, the CMPI standard |
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needs to clarify this and to make the existing providers backward |
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supported, this utility function - CMPI_CQL_NewSelectExp is provided |
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until the CMPI standard comes up with a conclusion on this. |
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When the CMPI provides a resolution on these issues, this utility |
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interface will be gone and unsupported. |
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Questions and Answers: |
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Q1: Is the CMPI Specification really ambiguous or does it |
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just not support CQL? If it's ambiguous should it be fixed |
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before it goes final? |
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A1:. Page 96 of the CMPI review spec states (line 2899-2901): The *projection output argument is |
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a pointer to a CMPIArray structure of CMPIString entries containing projection specification. |
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It shall be set to NULL if no projection is defined.. To clarify any ambigiuity, an e-mail to the |
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CMPI review group was sent, which would add the following: The projection specification is query |
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language specific. Hence the entries format of the projection output array CMPIString might be |
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different depending on the query language. Be sure to check the lang argument for the query language your |
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provider will support. . To guard the provider from DMTF's CQL possible ways it can be represented in |
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a string format, and since the CQL is experimental, the CMNewSelectExp will NOT support CQL. |
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The CMPI_CQL_NewSelect will support both CQL and WQL. |
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AQ:What happens if an existing Provider is passed a CQL |
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statement and issues a newSelectExp call? Does it return |
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an error? |
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A2: The error code CMPI_RC_ERR_QUERY_LANGUAGE_NOT_SUPPORTED would be set. |
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Q3: Both CMNewSelectExp and CMPI_CQL_NewSelectExp return a |
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CMPISelectExp. Is there anyway to determine whether the |
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CMPISelectExp represents a CQL or WQL expression? |
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A3:Not from the scope of the CMPISelectExp structure. Please note that the routine |
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that would exercise the CMPISelectExp has a char *lang passed in as argument. |
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This char *lang* can be used to easily determine what query language is used. |
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| Registering CMPI providers with Pegasus | Registering CMPI providers with Pegasus |
| --------------------------------------- | --------------------------------------- |
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