[Ace-users] [ciao-users] redundant component groups

[Friedhelm Wolf]

CIAO VERSION: 0.5.8
TAO VERSION : 1.5.8
ACE VERSION : 5.5.8

HOST MACHINE and OPERATING SYSTEM:
    i686 pc, SUSE linux Enterprise Server 9, Kernel 2.6.5

COMPILER NAME AND VERSION (AND PATCHLEVEL):
    gcc 3.3.3 (SuSE Linux)

THE $ACE_ROOT/ace/config.h FILE:
    #include "config-linux.h"

THE $ACE_ROOT/include/makeinclude/platform_macros.GNU FILE :
    include $ACE_ROOT/include/makeinclude/platform-linux.GNU

CONTENTS OF $ACE_ROOT/bin/MakeProjectCreator/config/default.features
    (used by MPC when you generate your own makefiles):
    N/A

AREA/CLASS/EXAMPLE AFFECTED:
    CCM deployment

SYNOPSIS:
    Which possibilities exist to have fault tolerance in CIAO and DAnCE?

DESCRIPTION:
Hi there,

The basic challenge, this post is about concerns fault tolerant behavior
of a system of CCM components. Thus, before becoming too specific:
Does anyone have some experiences with how to implement CCM systems,
which have to be very reliable in terms of uptime/availability?
What CCM mechanism are there to achieve this?

To become more specific now:
The following approach is inspired by the CORBA fault tolerance service:
The basic idea is, that a group of components (having interdependencies),
provides some services which need to have a very high availability.
So all components will be instantiated more than one time to have a
redundant backup
(keeping these components in sync might be necessary, depending on the
component
type but this is not in the scope of this question).
If one of these components fails (assuming that there is a way to find out
when a component
fails ... usually through CORBA exceptions), it will not only be necessary
to replace
this single component by its backup, but also to inform the whole component
group to reconnect
to the correct component.

Can you give me some advice, how to achieve this using standard CCM
mechanisms?

I think that ReDaC might aim in this direction.
Is it possible to dynamically create an assembly file, which reflects the
necessary connection
changes to integrate a backup component instead of an unresponsive
component?
Can you foresee any technical or performance problems, that would conflict
with such an approach?

Besides from technical issues:
ReDaC seems to be a nonstandard enhancement of the CCM spec by DAnCE.
Is that correct?

I ask this, because it's necessary for the project I work with to be based
on standards specifications
only at this level of the design. So, are there any efforts to standardize
the redeployment features?

Are there other CCM standard features, I didn't think about, which could
provide fault
tolerance on component assembly level.

Thanks for reading all through this rather long explanation and for giving
any helpful remarks,
Friedhelm
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