Applying RT-Policies in CORBA Component Model

August 20, 2002

Applying RT-Policies in CORBA Component Model

Nanbor WangDepartment of Computer ScienceWashington University in St. Louis

[email protected]

Washington University, St. Louis

Nanbor Wang Applying RT-Policies in CCM

Overview

• Component composition• RTCCM overview

– Why, where, and how

• Iterate thru proposed RT Policies in CIAO– What is the right granularity to apply the policy?– When (or where) to specify– Use case scenarios where the RTCCM approach

will/will not work– Does RTCCM approach impose any restrictions

on component developers/system integrators?



Component Packaging

IDL/CIDL Compiler

UserCode

GeneratedCode

IDL

ComponentDescriptor

DefaultProperties

Compiler

SharedLibrary or

Executable

Packaging Tool

ComponentPackage

.zip



Component Assembly

PropertiesDeploymen

tTool

AssemblyArchive

.aar (ZIP)

Assembly Tool

ComponentPackage

ComponentPackage

ComponentPackage

PortConnections

InstanceCreation

...



Composition Example• Application server

– run-time management– service initialization

• CCM Assembly Archive– Assembly descriptor

• Install components– Component

implementations– Component

descriptors– Configuration

property files• Establish connections

Application Server

Motor

modulator

controller

contrl_panel

modulator

position

EmStop

Location

position

Proximity

EmStop

Proximity

EmStop

Motor

Event Channel



Component Compositions

• An assembly descriptor specifies what component implementations are needed by referring to their component descriptors

• A Component descriptor (.csd) records component features and dependencies to other software modules

<!– Associate components with impls --><componentfiles> <componentfile id="Motor"> <fileinarchive name="AB-motor.csd"/> </componentfile>

<componentfile id="Location"> <fileinarchive name="linear-encoder.csd"/> </componentfile>

<componentfile id="Proximity"> <fileinarchive name="p-switch.csd"/> </componentfile>

<componentfile id="controller"> <fileinarchive name="AB-panel-if.csd"/> </componentfile> </componentfiles>



Component Instantiations

<!– Instantiating component homes/instances -->

<partitioning> <processcollocation> ...

<homeplacement id="ProximityHome"> <componentfileref idref="Proximity"/> <componentinstantiation id="left"> <componentproperties> <fileinarchive name="left-switch.cpf"/> </componentproperties> </componentinstantiation> <componentinstantiation id="right"> <componentproperties> <fileinarchive name="right-switch.cpf"/> </componentproperties> </componentinstantiation> </homeplacement> ... </processcollocation></partitioning>

• An assembly descriptor specifies how homes and components should be instantiated

• A component property file (.cpf) can be associated with a home or a component instantiation to override default component properties



Connecting Components

Application Server

Motor

modulator

controller

contrl_panel

modulator

position

EmStop

Location

position

Proximity

EmStop

Proximity

EmStop

Motor

Event Channel

<connections> ... <connectinterface> <usesport> <usesidentifier>modulator</usesidentifier> <componentinstantiationref idref=“Controller"/> </usesport> <providesport> <providesidentifier> modulator </providesidentifier> <componentinstantiationref idref=“Motor"/> </providesport> </connectinterface> <connectevent> <consumesport> <consumesidentifier>EmStop</consumesidentifier> <componentinstantiationref idref="Controller"/> </consumesport> <publishesport> <publishesidentifier> EmStop </publishesidentifier> <componentinstantiationref idref="left"/> </publichesport> </connectevent> ...</connections>

• Assembly descriptors also specify how component instances are connected tegether



RTCCM ≠ CCM + RTCORBA•Plain CCM has no mechanisms to specify and enforce RT policies

•RT policies need to be assured end-to-end for components & connections

•Trying to ensure RT policies are met in components leads to:– Tight couplings among

component implementations– Difficulty in reusing existing

components (without RT knowledge)

– Failure to utilize many RT mechanisms that go beyond component implementations•Component connections

–private connections–pre-connections

•Component collaborations–Thread pools–Thread borrowingRT Application Server (?)

Container

RT-ORB

CORBAComponent

ComponentHome

RTPOA

External

Interfaces

CallbackInterfaces

InternalInterfaces

Container

CORBAComponent

ComponentHome

RTPOA

External

Interfaces

CallbackInterfaces

InternalInterfaces

Why doesn't running a RTORB beneath CCM make

it an RTCCM implementation?



Real-time CCM (RTCCM)

• Abstracting RT CORBA related systemic (QoS) aspects– Specify RT policies of a

component instance– Specify RT policies of a

connection between components

– Allocating & computation and communication resources for components

– Specify sharing & collaboration of resources among components

– Configuring ORB with custom communication mechanisms and options

container

com

ponent

RT-ORB

container

com

ponent

OScustom

transport

Application Server

ORBPlugins

•Solution: Configure RT-policies/mechanisms using CCM’s metadata



RTCCM Component Packaging

IDL/CIDL Compiler

UserCode

GeneratedCode

IDL

ComponentDescriptor

DefaultProperties

Compiler

SharedLibrary or

Executable

Packaging Tool

ComponentPackage

.zip



RTCCM Component Assembly

PropertiesDeploymen

tTool

AssemblyArchive

.aar (ZIP)

Assembly Tool

ComponentPackage

ComponentPackage

ComponentPackage

PortConnections

InstanceCreation

...

ResourceAllocations

ORBExtensions

PriorityMappings



Component-Integrated ACE ORB (CIAO)

1.Component default priority model

2.Override component priority model

3.Priority level of a component instance

4.Defining thread pools5.Associate thread pools with

component instances6.Specify queuing policies7.Specify pre-connections8.Specify private connections9.Configure ORB components

•Custom protocols•Priority mappingsRT Application Server

Container

RT-ORB

CORBAComponent

ComponentHome

RTPOA

External

Interfaces

CallbackInterfaces

InternalInterfaces

Container

CORBAComponent

ComponentHome

RTPOA

External

Interfaces

CallbackInterfaces

InternalInterfaces

1

2

8

6

3

Thread Pool A

Priority30

Priority60

4

55

7

9

•CIAO’s will make RT policies an integral part of deployment metadata



RTCCM Descriptor Examples

• Component default priority model

<corbacomponent> ... <ciao:prioritymodelpolicy name=“priority_model_policy" value=“SERVER_DECLARED” priority=“20”/> ... </corbacomponent>

<partitioning> <processcollocation> ... <homeplacement id="ProximityHome"> <componentfileref idref="Proximity"/> <componentinstantiation id="left"> <componentproperties> <fileinarchive name="left-switch.cpf"/> <ciao:rtprioritylevel value="60"/> <ciao:rtprioritymodel value="CLIENT_PROPAGATED"/> </componentproperties> </componentinstantiation> <componentinstantiation id="right"> <componentproperties> <fileinarchive name="right-switch.cpf"/> <ciao:rtprioritylevel value="60"/> <ciao:rtprioritymodel value="CLIENT_PROPAGATED"/> </componentproperties> </componentinstantiation> </homeplacement> ... </processcollocation></partitioning>

• Override component priority model

• Specify the priority level of a component instance

• Associate component instances with customized protocols


Nanbor Wang Applying RT-Policies in CCMORB-level (component server instance)

Descriptors • Define thread pools• Plug in custom

protocol support• Define protocol

configuration• Plug in custom

priority mapping• Define priority-

banded connection policies

• Define QoS aggregates

<componentassembly> ... <partitioning> <ciao:createthreadpool id="tp_a" priority="30" number="10"/> <ciao:createthreadpoolwithlane id="tp_l"> <ciao:prioritylevel lane="30" number="3"/> <ciao:prioritylevel lane="60" number="3"/> <ciao:prioritylevel lane="80" number="10"/> </ciao:createthreadpool> <ciao:dependson type=“pluggable_protocol” id=“shmiop”/> <ciao:tcpprotocolproperties> <ciao:protocolproperties name=“no_delay” value=“true”/> <ciao:protocolproperties name=“send_buffer_size” value=“32768”/> </ciao:tcpprotocolproperties> <ciao:dependson type=“custom_priority_mapping” id=“lynxos_vme3”/>



RTCCM Descriptor Examples (cont.)

<homeplacement id="ProximityHome"> <componentfileref idref="Proximity"/> <componentinstantiation id="left"> <componentproperties> <fileinarchive name="left-switch.cpf"/> <ciao:usethreadpool idref="tp_a"/> </componentproperties> </componentinstantiation> <componentinstantiation id="right"> <componentproperties> <fileinarchive name="right-switch.cpf"/> <ciao:usethreadpool idref="tp_a“/> </componentproperties> </componentinstantiation> </homeplacement> <homeplacement id=“controlerhome”> <componentfileref idref=“controller”/> <componentinstantiation id=“control_module”> <componentproperties> <fileinarchive name=“controller.cpf”/> <ciao:usethreadpoolwithlane idref=“tp_l”/> </componentproperties> </componentinstantiation> </homeplacement>

• Associate thread pools with components

• Associate QoS aggregates with connections



Connection Policies

• Establishing pre-connections

• Establishing private connections

<connections> ... <connectinterface ciao:preconnect=“true” ciao:private=“true”> <usesport> <usesidentifier>modulator</usesidentifier> <componentinstantiationref idref="Motor"/> </usesport> <providesport> <providesidentifier> modulator </providesidentifier> <componentinstantiationref idref="Controller"/> </providesport> </connectinterface>

<connectevent ciao:preconnect=“true” ciao:connband=“highest”> <consumesport> <consumesidentifier>EmStop</consumesidentifier> <componentinstantiationref idref="Controller"/> </consumesport> <publishesport> <publishesidentifier> EmStop </publishesidentifier> <componentinstantiationref idref="left"/> </publichesport> </connectevent> ...</connections>



Other policies?

• Other RT policies?

Documents

Applying RT-Policies in CORBA Component Model