CXWS: Re-thinking CIMOM

Architecture

Architectural Overview

What is CXWS?

A Java-based CIMOM technology with:• Clean conceptual basis• Lightweight instances• Simplified provider development

Clean Conceptualization

• Object-oriented framework (meta-objects actually do things)

• Properties really get and set values• Instances and classes are always

fully functional, even if lazily realized

Lightweight Instances

• CIM class definitions impose structure on CIM instances

• CXWS leverages this structure as meta-data for instances

• A CxInstance is little more than a CxClass reference and an array of object values

• CxProperty objects know just which value to get or set (no overhead, no searching)

• Provision for lazily-populated instances, built directly from an object path

Superior Provider Interface

• Java WBEM Services (WBEMSolutions), OpenWBEM, Pegasus all have isomorphic provider interfaceso Merely “pass through” the original client

request, without adding value

• CXWS’ basic provider interface is one method, two argumentso The surprise: it’s not just simpler, it’s also

more powerful!

Association Creation: UML

JWS Providers

• references, referenceNames• createInstance, setInstance,

deleteInstance• execQuery

• enumerateInstances• enumerateInstanceNames• getInstance• associations, associationNames

CXWS Providers

• Typical “observational” providers implement just one method.

• An interface allowing manipulation of objects adds three methods (create, update, delete), but implementation is optional.

• Support for “lazy” instances is also optional; adds one additional method.

Fewer Execution Paths

for (Iterator paths = enumerateInstanceNames(…);

paths.hasNext(); )

{

CIMInstance inst =

getInstance((CIMObjectPath) paths.next(), …);

. . .

}

Fewer Execution Paths

for (Iterator insts = enumerateInstances(…);

insts.hasNext(); )

{

CIMInstance inst = (CIMInstance) insts.next();

. . .

}

Code stops working!

Client exercises a new code path

Basic Provider Interface

void enumerateDirectInstances(CxCondition cond, InstanceReceiver r) throws Exception

• A single all-purpose enumeration method with a simple signature.

• The condition argument tells what instances the caller wants.

• Candidate instances are passed to InstanceReceiver callback.

A Simple Provider

public void enumerateDirectInstances(CxCondition cond, InstanceReceiver r)throws Exception

{for (int ii = 0; ii < getHbaCount(); ++ii){ r.test(makeHbaInstance(ii));}

}

private CxClass cc = …;private CxProperty hbaIndex = cc.getExpectedProperty(“HbaIndex”);private CxClass hbaName = cc.getExpectedProperty(“HbaName”);

private CxInstance makeHbaInstance(int ii){

Object[] values = cc.getDefaultValues();hbaIndex.set(values, new Integer(ii));hbaName.set(values, getHbaName(ii));// . . .return new CxInstance(cc, values);

}

Conditions

• A generalization of object path• Like a WHERE clause in a query, but

only refers to one class (the condition’s domain)

• No parsing required• Support simple but powerful forms of

reasoning

Instance Receivers

• Originally conceived to avoid constantly concatenating Vectors

• Serendipitously, opens the door to:o Streaming resultso Asynchronyo Reporting partial operation failure

Typical Conditions

• For enumerateInstances: condition = CxCondition.ALWAYS

• For getInstance: condition encodes object path

• For references, associators: condition expresses a constraint on the “role” property (inferred if necessary)

• Providers should not make assumptions about the nature of the condition

Provider Structure

• Step one: nested loops• Step two: each loop body becomes a

separate method; “select or search” control strategy

• Step three (unusual): alternative selection strategies

Provider Example (Step 1)

public void enumerateDirectInstances(CxCondition cond, InstanceReceiver r)

throws Exception

{

for (Iterator systems = getAllSystems(); systems.hasNext(); )

{

System system = (System) systems.next();

for (Iterator devices = system.getAllDevices(); devices.hasNext(); )

r.test(makeInstance((Device) devices.next()));

}

}

Provider Example (Step 2)

public void enumerateDirectInstances(CxCondition cond, InstanceReceiver r)

throws Exception

{

if (cond.hasRestriction(systemName))

enumeratePerSystem(getSystem((String) cond.getRestriction(systemName)),

cond, r);

else

for (Iterator systems = getAllSystems(); systems.hasNext(); )

enumeratePerSystem((System) systems.next(), cond, r);

}

private void enumeratePerSystem(System system, CxCondition cond, InstanceReceiver r)

{

if (cond.hasRestriction(deviceId))

r.test(makeInstance (system.getDevice((String) cond.getRestriction(deviceId))));

else

for (Iterator devices = system.getAllDevices(); devices.hasNext(); )

r.test(makeInstance((Device) devices.next()));

}

Association Providers

• Can be written like any other provider• Or… use AssociationProvider abstract

class, based on “relations”• Relations describe how to compute

the Antecedent from the Dependent, or vice-versa.

• CIM_SystemDevice: trivial to identify the CIM_System associated with a CIM_Device

Implementing CIM Methods

• CXWS dispatches CIM methods using Java reflection

• Provider just implements a Java method whose name and type signature matches that of the CIM method

• Providers don’t have to dispatch methods, in the style of invokeMethod()

Provider Interface Extensions

• LifecycleProvider adds createInstance, setProperties, deleteInstance.

• PartialInstanceProvider allows an object path to be used as an instance.If and when access to non-key properties is

required, the provider’s retrieveValues method will be called.

• DispatchingMethodProvider allows a provider to take more active control over dispatching a CIM method call.

Query Processing

• The WHERE clause can be processed into a necessary condition for any variable

• Providers already know how to optimize their search based on conditions, without additional work

• The condition tends to be more specific if other variables’ values can be assumed, so…

• The query engine tries to be clever in ordering query variables

• Query engine recursively processes query variables to achieve effect of nested loops

select hba.index, port.index

from AixHbaPort port,

AixHostBusAdapter hba,

AixHbaControlledBy cb

where hba.manufacturer = “QLogic”

and port = cb.dependent

and hba = cb.antecedent

Query Processing

Pseudo-code for execution plan:foreach (hba such that

manufacturer = “Qlogic”){

foreach (cb such that antecedent = hba){

// port is uniquely// determinedlet port =

cb.dependent;

produce(hba.index, port.index);

}}

select hba.index, port.index

from AixHbaPort port,

AixHostBusAdapter hba,

AixHbaControlledBy cb

where hba.manufacturer = “QLogic”

and port = cb.dependent

and hba = cb.antecedent

The CXWS Eco-System

• CXWS framework• CIM-XML over HTTP

servlet (DSP0200, DSP0201)

• CIM-RMI interface (JSR-47)

• Streaming RMI interface for CIMOM

• RMI interface for host agents

• MOF compiler• Query engine

• Simple instance repository

• JwsProviderConverter adapts Java WBEM Services (JWS) providers to CXWS

• Reflective CIM model for controlling the CIMOM

• Interface generator for constructing Java interfaces from CIM class definitions

Cxws_ClassToProvider

Management of CXWS is performed by operating on a CIM model of CXWS itself, in the root/reflection namespace:

• All CIM classes modeled as instances of the CIM class CXWS_Class.

• All Java provider instances exposed by CXWS_Provider CIM class.

• Creating an instance of CXWS_ClassToProvider association actually binds a CIM class to its provider.

• Separates provider from CIM class definition

CXWS_ClassToProvider Example

#pragma namespace("root/reflection")

instance of CXWS_ClassToProvider

{

Antecedent = "root/reflection:CXWS_Provider." "JavaName=\"com.appiq.cimom.aix.AixComputerSystemProvider\"";

Dependent = "root/reflection:CXWS_Class."

"NamespaceName=\"root/cimv2\","

"Name=\"APPIQ_AixComputerSystem\"";

};

Generated Provider Interface

• Automated tool generates Java symbolic constants from CIM namespace:o Class nameso Property nameso ValueMap values

• Also generates static members for the class and property objects, not just names.

Generated Interface

/**** Interface file generated from CIM class definition

for APPIQ_AixComputerSystem ****/

public interface AixComputerSystemProviderInterface extends Provider

{

public static final String APPIQ_AIX_COMPUTER_SYSTEM = "APPIQ_AixComputerSystem";

. . .

public static final String CREATION_CLASS_NAME = "CreationClassName";

public static final String DEDICATED = "Dedicated";

public static final UnsignedInt16 DEDICATED_ACCESS_SERVER = new UnsignedInt16(9);

. . .

public static final String _CLASS = "APPIQ_AixComputerSystem";

public static final String _NAMESPACE = "root/cimv2";

public static final String _SUPER = "APPIQ_ComputerSystem";

public static final CxNamespace _namespace =

CxNamespace.getExistingNamespaceOrNull(_NAMESPACE);

public static final CxClass _class = _namespace.getExpectedClass(_CLASS);

public static final CxProperty caption = _class.getExpectedProperty(CAPTION);

public static final CxProperty description = _class.getExpectedProperty(DESCRIPTION);

. . .

}