Transcript Building WSRF services - Dipartimento di Matematica e

Building services in WSRF
Ben Clifford
Draft 2004-07-09
For GGF summer school, July
2004
outline
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Webservices – should be covered by EGEE, so just one slide of concepts,
eg. WSDL without further expl.
WSRF – what WSRF adds – do we need to discuss why or will that be
covered in earlier sections? Eg. Carl’s intro?
Introduce WS-Resource
WS-Resource Properties
Exercise: stand up supplied installation and get running (maybe before
WS-Resource intro)
Exercise: talk to someone else’s service on a different laptop
Exercise: add a resource property to the service – add one which is ‘last
incremeted time’. Query own counters and query other peoples’ counters.
* Advanced students add another one of their choice.
Exercise: lifetime management: create new counters. Destroy old
counters.
Exercise: create a new counter resource and then register it to service
group – front screen will display fishies. (advanced exercise: if fish has a
FishName RP, use that instead of IP address)
2 hours exercise = 60 slides = 15 slides per module
Module 1
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Overview
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WSRF
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Globus Alliance WSRF implementation
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TODO: module 1 taught material should be
brief so that hands on happens soon –
could move some material to later on.
WSRF
WSRF is a framework consisting of a number of standards.
 Resource Properties *
 Lifetime management *
 Service Groups
 Notification
 Faults
 Renewable References (unpublished)
Other WS specifications such as:
 WS-Addressing *
* will be talked about in this tutorial
How WS-RF fits in with other web
service standards.
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TODO: chart with WSDL and SOAP, then
WSRF standards on top – maybe a slide in
WSRF into material?
Introduction to GT4 hosting env
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Describe components
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Container (TODO: slide with chart)
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Clients
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Build tools
(insert slides from sam’s tutorial here?)
WS-Resources
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Already know what a web service is
Web services should be stateless
But there is often state in the system
A WS-Resource is a representation of some
state that can be accessed through web
services
In this tutorial we will be using ‘counter’
resources which are simple accumulators.
WS-Resources
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WSRF specifications provide:
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XML-based Resource Properties
Lifetime management (creation/destruction) of
resources
Servicegroups, which group together WSResources
Notification
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(for example of changes in resource properties)
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Faults
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Renewable References
Web service
Web service
Web service with WS-Resource
Web Service with WS-Resources
Web Service with WS-Resources
WS-Resources
Examples of what could be a WSResouce?
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Files on a file server
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Rows in a database
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Jobs in a job submission system
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Accounts in a bank
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In this tutorial, each resource is a counter.
Files used in the exercise
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WSDL and XML Schema:
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Counter port type
Java
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CounterService.java
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CounterHome.jav
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Counter.java
Build.xml
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Tells Ant how to build and deploy the code
Exercise 1
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Exercise: stand up supplied installation and check it
works.
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Steps:
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Install software.
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Start the container.
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ant startContainer
Interact with container
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show-counter – shows the value in the counter
increment-counter – increases value of counter
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DO EXERCISE AT THIS POINT
Exercise 1 overview
One host (your own machine)
One web service running on own machine
One counter resource, which will already exist
Client running on own machine
Counter service
C
Client
One counter resource
Container
Exercise 1 overview
Counter service
ant startContainer
Starts up container,
with counter service
and a single counter
resource.
C
One counter resource
Container
Exercise 1 overview
show-counter and
increment-counter
clients interact with the
resource through the web
service.
Counter service
C
Client
One counter resource
Container
Module 2 – Resource Addressing
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Endpoint References
TODO: counter service should initialise
with two counter resources by default (or
part of exercise is to modify code to do
this? This is probably better)
Why?
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Need some way to refer to web services
and WS-Resources from anywhere on the
network.
Endpoint References
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WS-Addressing specification
An Endpoint Reference (EPR) points to a
web service by including a URL.
Endpoint References
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WS-Addressing specification
An Endpoint Reference (EPR) points to a
web service by including a URL.
TODO: paste in example EPR here
Endpoint References
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WS-Addressing specification
An Endpoint Reference (EPR) points to a
web service by including a URL.
EPRs can also contain extra information
For WSRF, include ReferenceProperties that
identify a resource
Endpoint References
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WS-Addressing specification
An Endpoint Reference (EPR) points to a
web service by including a URL.
EPRs can also contain extra information
For WSRF, include ReferenceProperties that
identify a resource
TODO: paste EPR with RefProps
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A WSRF conformant EPR contains:
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URL of web service
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Key to resource for that service
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Possibly other information
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Security
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Renewable References
Exercise 2
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Exercise 2a: talk to second counter on own
machine
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Exercise 2b: talk to someone else’s service on a
different laptop
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Using local-b.epr
Using other.epr
Use same clients as before, but specifying an EPR
file
Should be able to run all of the clients against any
machine.
Exercise 2 scenario
Two hosts (your own machine and your friend’s machine)
One web service running on friend’s machine
One counter resource on friend’s machine
Client running on your own machine
Exercise 2 scenario
Client can talk to everyone’s servers – so the situation in
this room looks more like this.
Module 3 – Resource Properties
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Resources have Resource Properties
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Use of XML
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Resource Properties element in WSDL
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Querying Resource Properties
Why?
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Resources represent state
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Often we want to inspect that state
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In this tutorial, we want to know the value
stored in each counter
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(the show-counter client)
XML based
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Each resource has a Resource Properties
document.
Defined in XML schema
Each element in the Resource Properties
document is a Resource Property (RP).
Ways to access RPs
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Pull
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Client can query the RP document
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GetResourceProperty
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GetMultipleResourceProperties
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QueryResourceProperties
Push
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Allows services to send changes in their
resources’ RPs to interested parties.
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WS-Notification
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Not covered in this tutorial
Pull operations
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GetResourceProperty
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GetMultipleResourceProperty
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Requests a single resource property by
name
Requests several resource properties (from
the same resource) by name
QueryResourceProperties
More advanced queries against RP
document.
 eg. XPath
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Exercise 3
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Exercise: add a resource property to the
service to give ‘last incremented time’.
Modify ‘show-counter’ to query this RP.
Query own counters and query other
peoples’ counters.
If time, can add another RP of own choice.
settable message
 some other statistic such as ‘number of
times queried’
 counter creation time
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Module 4 – Resource Lifetime
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Creating new resources
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Destroying old resources
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Soft-state lifetime management
Why?
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Resources come and go
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For example:
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jobs in a batch submission system could be
represented as resources
submitting a new job causes a new resource
to be created
when the job is completed, the resource
goes away
Creating new resources
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Factory pattern
A web service operation causes a new
resource to come into existence.
For example, in job submission:
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submit(JobDescription)
Destroying resources
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Two ways:
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Immediate Destruction
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Scheduled Destruction
Immediate destruction
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Destroy the resource now!
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Destroy operation
Scheduled Destruction
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Scheduled destruction allows soft
management of state.
TerminationTime RP
Keep state alive for as long as we need it,
by calling SetTerminationTime operation
periodically.
Scheduled Destruction
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Remote service is ‘self-cleaning’
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old unwanted state gets cleaned up
automatically if no-one keeps it alive
Problem: if interested party is
disconnected from network for a long time,
then it cannot extend lifetime and state
may be cleaned up prematurely.
Soft-state
time
TODO
Exercise 4
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Exercise: create new counters. Destroy old
counters.
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Two new clients:
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make-counter
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destroy-counter
Exercise 4 scenario
Created new counters
Destroyed existing counters
A Brief Overview of the rest of WS-RF
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WS-Resource Properties *
WS-Resource Lifetime *
WS-Servicegroups
WS-BaseFaults
WS-Renewable References
WS-Notification
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* already covered
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WS-ServiceGroups
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TODO
WS-BaseFaults
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TODO
WS-Renewable References
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TODO
WS-Notification
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A group of 3 standards
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Can deliver notifications of events
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For example, change in value of a resource
property
fin