Distributed OSGi, Dynamic wiring

["Konradi, Philipp" <ph...@siemens.com>]

Hi all,

I keep an eye on Tuscany already for a longer time. It's definitely a
great and very promising framework evolving here. 
The development goes on at such a high pace that it's not always easy
for me to stay updated about the features it supports :-)
Currently I'm wondering about two things:
a) With 2.x branch became a base technology for Tuscany runtime. What
are the plans about supporting the upcoming Distributed OSGi (RFC 119)
standard? Any activities going on currently? Sources in trunk to play
with?
b) Does Tuscany supports already dynamic wiring between components e.g.
when a service goes down, that a client consuming that service get
rewired to another service instance?

Any hints or pointers to existing information is really highly
appreciated!

Regards, 
Philipp 

RE: Distributed OSGi, Dynamic wiring

["Konradi, Philipp" <ph...@siemens.com>]

Hi Simon, Raymon

 

Thanks for the quick responses.

Comments inline...

 

Thanks, 

Philipp

 

From: Raymond Feng [mailto:enjoyjava@gmail.com] 
Sent: Wednesday, February 11, 2009 5:39 PM
To: dev@tuscany.apache.org
Subject: Re: Distributed OSGi, Dynamic wiring

 

More comments in line.

 

Thanks,

Raymond

 

From: Simon Laws <ma...@googlemail.com>  

Sent: Wednesday, February 11, 2009 12:53 AM

To: dev@tuscany.apache.org 

Subject: Re: Distributed OSGi, Dynamic wiring

 

Hi Philipp 

	 

	a) With 2.x branch became a base technology for Tuscany runtime.
What are the plans about supporting the upcoming Distributed OSGi (RFC
119) standard? Any activities going on currently? Sources in trunk to
play with?


Would be good to have Tuscany/SCA play the role of the distirbution
layer underneath OSGi. Nothing happening yet in Tuscany as far as I
know.  

 

I have RFC 119 on the radar but nothing has happened yet. It is a great
idea to have Tuscany/SCA be a distribution layer for RFC 124. At this
moment, we are building the Tuscany runtime with OSGi as the
infrastructure. And we will move up into the application level to
support RFC 119. If you are interested in this area, I would be glad to
help. 

[Konradi, Philipp] Yeah, definitely. Though Tuscany already now supports
OSGi contributions (implementation.osgi), I see a lot of advantages in
supporting the upcoming Distributed OSGi standard, which defines
integration of any middleware into an OSGi container. I think many
developers of OSGi-based apps would like to use on-board means if they
exist. And at the latest after EclipseCon, there will be many people
looking for RFC119-supporting middleware solutions. Tuscany with its
flexibility, SCA-support, rich set on supported bindings and running on
top of OSGi itself could be a great alternative for them. 

The Discovery parts of RFC 119 could also be interesting for Tuscany to
interop with other infrastructures e.g. other SCA-runtimes
(Inter-Domain-Interop), a use case which is not so rarely in big
companies. Tuscany might make use of an existing Discovery Service
implementation for this purpose (I'm actually involved in implementation
of one and which is planned to be open-sourced at ECF, Eclipse
Communication Framework, soon). 

Not sure whether I can contribute a lot to the coding, but as somebody
who worked in the RFC 119 team and in Discovery Reference Implementation
I can for sure help in spec clarifications, in discussions on the
mailing list,  check compliance and be a beta tester.

	b) Does Tuscany supports already dynamic wiring between
components e.g. when a service goes down, that a client consuming that
service get rewired to another service instance?


Not at the moment. Our domain is static to the extent that all
contributions must be present and endpoints resolved before you start
any nodes. A way of providing some resilience  with this scheme is to
run a node in a cluster and rely on a network sprayer to do the
re-routing for you. We are looking at refactoring our endpoint support
as we've had requests to support later binding from various people. Just
about to start in 2.x

[Konradi, Philipp] Many of the projects I know require beside the
availability requirements also addition, update and removal of
components/whole nodes at a later point in time and restart the whole
domain is unfortunately  not an option for them. I look forward to 2.x.

 

Are you mostly focusing on the OSGi environment to have Tuscany support
dynamic wiring? For example, SCA contributions are packaged as OSGi
bundles and they can be installed/uninstalled. Then some of the SCA
domain-level wiring needs to be synchronized upon these events. 

 

Or do you look into a broader scope, such as a set of nodes that form a
group (using a p2p protocol) which represents the SCA domain and they
exchange metadata within the group? As the configuration changes, the
SCA domain needs to rewire the components dynamically.

[Konradi, Philipp] Actually we have both use cases in our focus.


If you've got ideas feel free to jump in. 

[Konradi, Philipp] We've used discovery / distributed registry for this
purposes. When a service starts up or is shutdown, this is published to
all other nodes of the system. Those node check whether some service
reference can be satisfied now or need to be rewired to another existing
service. 

The knowledge about other existing services can also be used by service
proxies to switch transparently to another service if the one they
called failed, or for load-balancing purposes (kind of client-side
load-balancing). Such proxies can be called kind of smart-proxies. I
could imagine support for such smart proxies in Tuscany as well and
intents would be great to do that e.g. configuring "automatic-fail-over"
intent on service reference makes the proxy behave in the required way,
releasing business logic to take care of such issues. 

Does Tuscany use some kind of dynamic distributed registry internally? 

BTW: It might be worth a thought to use RFC 119 discovery service for
that purposes (incl. distribution of domain metadata)  since 2.x branch
is anyway based on OSGi. 

Simon

 

Re: Distributed OSGi, Dynamic wiring

[Raymond Feng <en...@gmail.com>]

More comments in line.

Thanks,
Raymond


From: Simon Laws 
Sent: Wednesday, February 11, 2009 12:53 AM
To: dev@tuscany.apache.org 
Subject: Re: Distributed OSGi, Dynamic wiring


Hi Philipp 



  a) With 2.x branch became a base technology for Tuscany runtime. What are the plans about supporting the upcoming Distributed OSGi (RFC 119) standard? Any activities going on currently? Sources in trunk to play with?


Would be good to have Tuscany/SCA play the role of the distirbution layer underneath OSGi. Nothing happening yet in Tuscany as far as I know.  

I have RFC 119 on the radar but nothing has happened yet. It is a great idea to have Tuscany/SCA be a distribution layer for RFC 124. At this moment, we are building the Tuscany runtime with OSGi as the infrastructure. And we will move up into the application level to support RFC 119. If you are interested in this area, I would be glad to help. 


  b) Does Tuscany supports already dynamic wiring between components e.g. when a service goes down, that a client consuming that service get rewired to another service instance?


Not at the moment. Our domain is static to the extent that all contributions must be present and endpoints resolved before you start any nodes. A way of providing some resilience  with this scheme is to run a node in a cluster and rely on a network sprayer to do the re-routing for you. We are looking at refactoring our endpoint support as we've had requests to support later binding from various people. Just about to start in 2.x

Are you mostly focusing on the OSGi environment to have Tuscany support dynamic wiring? For example, SCA contributions are packaged as OSGi bundles and they can be installed/uninstalled. Then some of the SCA domain-level wiring needs to be synchronized upon these events. 

Or do you look into a broader scope, such as a set of nodes that form a group (using a p2p protocol) which represents the SCA domain and they exchange metadata within the group? As the configuration changes, the SCA domain needs to rewire the components dynamically.

If you've got ideas feel free to jump in. 

Simon

Re: Distributed OSGi, Dynamic wiring

[Simon Laws <si...@googlemail.com>]

Hi Philipp

>
> a) With 2.x branch became a base technology for Tuscany runtime. What are
> the plans about supporting the upcoming Distributed OSGi (RFC 119) standard?
> Any activities going on currently? Sources in trunk to play with?
>

Would be good to have Tuscany/SCA play the role of the distirbution layer
underneath OSGi. Nothing happening yet in Tuscany as far as I know.

> b) Does Tuscany supports already dynamic wiring between components e.g.
> when a service goes down, that a client consuming that service get rewired
> to another service instance?
>

Not at the moment. Our domain is static to the extent that all contributions
must be present and endpoints resolved before you start any nodes. A way of
providing some resilience  with this scheme is to run a node in a cluster
and rely on a network sprayer to do the re-routing for you. We are looking
at refactoring our endpoint support as we've had requests to support later
binding from various people. Just about to start in 2.x

If you've got ideas feel free to jump in.

Simon