Node ServicesDevelopment

Thomas D. Uramturam@mcs.anl.gov

Argonne National Laboratory

Access Grid ArchitectureVenueServerVenueServer

VenueVenueVenueVenueVenueVenue

VenueClientVenueClient

NodeNode

• VenueServer– Server component for

Venues

• Venue– Virtual representation of a

meeting room

• VenueClient– User software for entering

a Venue

• Node– Aggregation of hardware

and software for participating in a meeting

NodeNode

Node Architecture

NodeServiceNodeService

ServiceManagerServiceManager

AGServiceAGService

• NodeService– Aggregates ServiceManagers– Manages node configurations

• ServiceManager– Exposes available machine

resources– Manages AGServices

• AGService– Interface for controlling access

to machine resources– Exposes service configuration

interface

Overview

• Expose machine resources– Describe available resources (e.g. video card)

• Provide configuration layer– Describe available configuration parameters

(e.g. video quality level)– Accept configuration of those parameters

• Provide service abstraction– Services are controlled over SOAP interface, so

could be written in any language with an interoperable SOAP implementation

Operation

• Resources– Resources represent something the machine

can make available (e.g. video capture device)

– When a service is added, it may have a resource assigned to it

Operation

• Service Capabilities– The capabilities of the node

are collected and passed to the venue

– Capabilities are currently defined with the following attributes:

• role (e.g. producer, consumer)• type (video)• codec (h261, dv)• rate• channels

NodeNode

Venue ClientVenue Client

VenueVenue

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Operation

• Capabilities Negotiation– The capabilities of the node are

collected and passed to the venue– The venue allocates a stream

(multicast group) for each producer capability of a yet non-existent type

– The venue returns a stream (multicast group) for each existing consumer capability type

– The returned streams are passed down to the services

NodeNode

Venue ClientVenue Client

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Operation

• Stream Descriptions– The venue returns a stream

description (multicast group) for each existing consumer capability type

– The returned stream descriptions are passed down to the services

– Service configure for the given streams (typically passing the contained multicast groups to media tools)

NodeNode

Venue ClientVenue Client

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Update AGServices

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Configuration

• Services may have a set of configurable parameters that control their operation– For example: video quality level, audio input

gain• Configuration parameters are defined in

terms of types from AGParameter.py– ValueParameter– TextParameter– OptionSetParameter– RangeParameter

• Basic handling of parameters is performed in AGService

Configuration

• The Node Management user interface includes code to represent parameters for editing

TextParameter

OptionSetParameter

RangeParameter}}

Configuration

• Parameter values can be used when the service is started

• Configuration data is persisted in saved node configuration files– ConfigParser format– Stored in AccessGrid/nodeConfig

Other

• Logging– Services derived from AGService

automatically create a logfile in AccessGrid3/Logs, based on Service class name

Packaging

• A service is delivered in a service package, a zip-file containing the Python implementation, a service description file, and any supporting implementation files

• A service description file (.svc) contains information presented to the user before adding the service

• Service packages are installed using agpm (similar to shared applications):– runag3.py agpm3.py -z ServicePackage.zip

• Service packages are extracted to a temporary directory, subject to their version

Packaging

• Sample service description file[ServiceDescription]name = DebugServicedescription = Example Debug Servicecapabilities = Capability1 Capability2 Capability3executable = DebugService.pyplatform = neutralversion = 1.0

[Capability1]role = consumertype = audio

[Capability2]role = consumertype = video

[Capability3]role = producertype = debug

AGService API

Calls from Toolkit

• On Enter– GetCapabilities()

• Called during aggregation of capabilities from AGServices– ConfigureStream(StreamDescription)

• Called to set the stream the AGService should use• Ignores trivial stream changes

• On Exit– Stop()

• Called to stop the AGService

• Other– Start()

• Not called explicitly• Typically called from ConfigureStream

Example: DebugService

• Basic service that – logs messages in response to various

calls to it– defines debug parameter which can be

set through configuration interface

• Review log file (DebugService.log) for proper operation

Exercise: ClientAnnouncerService

• Service to announce presence• Sends user’s name over a multicast

group• Watch for your name to appear on

the ClientViewer

Exercise: ClientAnnouncerService

• Retrieve Venue URL from VenueClient

• Send Venue URL with name• Use fixed multicast address, to share

presence data across Venues