RE: [wsdm] Discovery Scenarios [fred]

I think we do need to have a "ListResources" functionality for
each manageability provider.  This model is used by multiple agent
based management systems, JMX and HP's WSMF are good examples of
it.

The functionality itself can actually be handled like a
relationship  named "manages" and/or
"isManagedBy" which can exist between the manageability
provider and each EPR. 

Discovering new EPRs or changes in the EPR list can be done through
relationship change notifications.  We haven't talked much about
relationships yet in this group but it will probably provide a mechanism
to notify the manager of any relationship change, hence we get the
functionality for free in this context.

thanks

Thierry Schang

TIBCO Software Inc. - voice: 650 846 5781

At 01:14 PM 5/21/2004, Mike Clements wrote:

Consider
an optional ListResources operation on a resource manager, which returns
all known resources it is managing. If this function exists, it does not
necessarily imply anything about how the data got there. And consumers of
the management service don't necessarily care how the data got
there.

 

I think different ways
of taking resources under management fall into 2 categories. Either the
manager discovers the resources on its own, or it's told to manage the
resources. It could be told by a human, by the resources
self-registering, or anything else. Both techniques are commonly
used.

 

If we have a
"ListResources" operation, should the spec discuss how the
manager knows when to update the list? We might want to avoid doing that.
It mabe a slippery slope which leads to strapping a rocket booster to a
Toyota.

 

IMO this is also the
problem with covering install / deploy. Metrics have a base set of
primitive stuff, some kind of greatest common denominator across all
kinds of different "stuff": counts, up/down, etc. Install /
deploy varies so widely that greatest common denominator isn't big enough
to be useful.

 

From: David E Cox
[mailto:]

Sent: Friday, May 21, 2004 11:49 AM

To: John DeCarlo

Cc: Wsdm (E-mail)

Subject: Re: [wsdm] Discovery Scenarios [fred]

Hi John, thanks for your responses. 

I'm not sure I agree that #1 is completely out of scope
for WSDM.  For MOWS, I see it as completely in scope.  For
MUWS, it may also be in scope for resources where a management system can
be responsible for install/deploy of the resource (such as
software).  I don't know why we tackle metrics, configuration,
relationships, and so on without tacking install / deploy, at least at
some point in the future.  It is a perfectly valid management
capability.  Do we consider that covered by another group?

For #2, I understand that we can't dictate how it
happens, but we can put requirements on the result so that we can manage
the environment.  For example, if we assume the manager has a WSDL
(which is the premise for the scenario) then we have a requirement on the
installation of the resource or on the environment at large that the
management interfaces be published in a registry somewhere that the
management system knows to look at.   

Let me get concrete again, to try to explain
myself.  For network resources, management tools tend to find the
resources (via broadcast, looking at router tables, etc).  The tool
then finds the management interface (try the SNMP port, etc).  For
system resources, the tools look for the resources themselves with
scanners (file signatures or registry entries for applications, OS device
registry for hardware, etc) and then looks for the appropriate management
interface.  Usually, the management interface is provided by some
hosting environment for the resource (such as the OS or the app
server).  I can think of very few scenarios where the management
tool discovers or enumerates the management interfaces first, and then
tries to find the resources behind the interfaces.  In those few
cases I can think of, the tools would tend to go to the management
interface of the OS or other hosting environment to enumerate the
resources, not to the resource management interface itself.  For
example, the manager would ask the OS or SAN about the disk drives; it
wouldn't look for the disk drive's management interface first.  If
we're going to change that paradigm, I'd like to understand the
underlying scenario in more detail. I think it puts a new requirement on
hosting environments that we may not be able to dictate. 

Please note that I am not trying to say that your
(collective) underlying assumption is false.  Finding WSDLs in a
well-known registry is a pretty obvious pattern for discovery.  I'm
just trying to bring it down to earth for real resources and how they
will really get discovered. 

Regards,

David E Cox 

John DeCarlo <>

05/21/2004 11:01 AM 

To

"Wsdm (E-mail)" <> 

cc

David E Cox/Raleigh/IBM@IBMUS 

Subject

Re: [wsdm] Discovery Scenarios [fred]

David,

See inline.

David E Cox wrote:

> 

> Hi Fred,

> 

>   Thanks for writing this up.  To me, the confusion starts before your 

> scenario begins.  

Ah ha!

>   How did the managed resource get installed into the system?

There are at least two items to consider here.  1) Installing the 

resource and making it available to consumers.  2) Making the resource 

manageable.

1) is out of scope for WSDM

2) is not well defined how it happens.  (Probably because how you make a 

disk drive manageable will differ from how you make a Web Service 

manageable, and even the Web Service may provide its own manageability 

or rely on the Execution Environment or something else.) But essentially 

it involves some method where the Manageability Provider is linked 

enough to the resource to start providing manageability for it.

In the last call, we talked about having an Event defined that says a 

resource has now been made manageable.

Otherwise, we really don't know what resources have been made manageable 

without talking to the manageability provider.

Not that there aren't lots of good ideas on changing that, like perhaps 

registering all EPRs somehow when the resource is made manageable. 

Maybe the registries would just subscribe to the "JustNowMadeManageable" 

Event, as any other consumer would.

>  Who installed it?  

Again, make the resource available for consumers is out of scope for 

WSDM.  Only making it manageable is in scope.

The answer is similar to the last question.

> Who published its management interface, and to where? 

This depends on who provides manageability for the resource.  The 

management interface is defined in WSDL and may already have been 

published in a registry somewhere, or the URL to the WSDL has been 

provided somehow.

So the manageability provider (whoever that happens to be, and there may 

be more than one) publishes the manageability interface in WSDL.

>  Who made the resource known to the resource manager (in some cases they 

> will be installed concurrently, in some cases they will be separate).

This is the basic question.

Maybe no one made the resource known the the resource manager.  So it is 

required to continually do some sort of discovery.

Maybe if WSDM or another group defines a "just made manageable" event, 

the resource manager could just subscribe to it.

>   I think that part of the scenario is what drives the WSDL vs EPR 

> starting point.  I at least am confused about how/why a manager would be 

> given a WSDL file.  That's not typically the way a management tool would 

> discover a manageable resource.  It usually finds the resource first (by 

> looking in directories and registries, or by various scanning 

> techniques), then finds the manageability interface.  I'm not saying 

> that is right or wrong in the new Web Services model, but I would like 

> to understand that part of the scenario.

Let me word it another way.  Management tools are either pre-loaded with 

information about resources to manage, or they have to do some sort of 

discovery.

One idea in the MUWS world is to simply discover the Manageability 

Endpoint WSDL.  Then query the Manageability Provider at that endpoint 

to find out what manageable resources there are there.

And where there are multiple manageability interfaces for one resource, 

the management tool may or may not care, and may or may not want to use 

Identity or Correlatable Names to determine if two resources are the same.

Does this answer your questions?

-- 

John DeCarlo, The MITRE Corporation, My Views Are My Own

email:      

voice:      703-883-7116

fax:        703-883-3383

DISA cube:  703-882-0593

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