Hi,
Please see my comments inline below.
Thanks,
Raymond
----- Original Message -----
From: "Simon Laws" <[EMAIL PROTECTED]>
To: "tuscany-dev" <[email protected]>
Sent: Monday, June 18, 2007 5:25 AM
Subject: Domains, runtimes, components and cardinality
Following on from recent discussion on the distributed binding (I've been
putting notes here [1])... In a Tuscany SCA runtime what do we expect the
cardinality between the various parts of it to be?
A domain notionally runs on a runtime. In the case of a stand-alone
Tuscany
SCA runtime this will be a single process (C++ exe, Java VM etc.). In the
case of a distributed Tuscany SCA runtime, the runtime is made up of many
distributed nodes that each run parts of the domain.
1/ Can domains share runtimes/nodes?
I.e can components from more than one domain be running inside a single
Tuscany SCA runtime or is the user expected to start up multiple runtimes
to
run multiple domains.
I think a single Tuscany SCA runtime can only join one SCA domain. For a
single machine (node), we can have multiple runtimes. These runtimes will
have to share the resources, for example, using different ports for the http
protocol. I'm not sure if we need to have the node
concept between the SCA domain and runtime.
2/ How many nodes can a single component run on?.
I.e. is the assignment of a component to multiple nodes, for performance,
reliability etc. reasons, explicitly supported as part of the topology
description of a distributed domain. If so then the SCA binding chooses
which node to use. If not then any distribution of workload is considered
to
be a job for the node implementation.
We might have different cases here:
1) For load-balancing, we can assign a component to multiple runtimes
2) For a singleton service, we may have to assign it to a single runtime (a
backup runtime can be picked for HA).
I'd be interested to hear peoples views on this
My starting point is...
1/ No, we will support multiple domains by starting multiple runtimes. We
could add the extra function to support sharing of runtimes between
domains
in the future if it's found to be required.
2/ We shouldn't restrict whatever structure we use to describe the
component/node association to be 1-1. But we can assume 1 in the first
instance and consider adding more complex node selection features to the
SCA
binding in the future.
Regards
Simon
[1] http://cwiki.apache.org/confluence/pages/editpage.action?pageId=59826
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