[Openais] A few Questions to OpenAIS

Steven Dake sdake at redhat.com
Tue Apr 24 15:52:53 PDT 2007

On Sun, 2007-04-22 at 08:11 +0200, Patrick Schwarck wrote:
> Dear Mailing Group, 
> i would like to know several things about the usage or the experiences
> you 
> have with openAIS. 
> As i'm writing a thesis about HA Frameworks fitting to several
> requirements of my 
> company i would like to know: 
>    * does the OpenAIS support the use of a status. What i mean with
> this, 
> that the frameworks supports the calculation of a status symbol (for
> example a trafficlight)

I am not really sure I understand your question.  AMF follows the SA
Forum standard and implements several state variables which can be read
in the SA Forum API documentation for AMF.  Specifically it supports an
HA State which may be Active/Standby.

Also other APIs are supported which allow one node to send messages to a
group of nodes.  This service is called the closed process group
service.  It is fully documented in man pages.

It is also possible to use the checkpoint API to have an active
application record a status variable.  Then if the active application
fails, the standby could retrieve this status variable from the
checkpoint service.

Read the APIs described at

> and sending this status to some kind of client for showing up. If it
> is not supported, where and/or 
> how could this be added as a module?

To add modules, you could either use one of the existing services such
as CPG for your cluster communication or you could add a plugin module
which uses totem directly.  For information on adding a direct plugin
into openais, see:


>    * how many processes are startet/running on a host with openais? 
> How many processes are running on each node? (What das PS show you?`)
> Are the Nodes the "only" binary and the  Interface just libraries? 

Each node runs 1 aisexec process.  This process loads all of the
services available via openais into its address space and makes uses of
one set of cluster infrastructure to execute the cluster infrastructure.

An application that wishes to communicate with aisexec links to a shared
object (library) and uses the SA Forum or openais APIs as desired.

If AMF is enabled, applications will be started by openais depending
upon the AMF configuration file (ie: openais's AMF service acts like
init starting services and maintaining them in active or standby state).

A bit more detail on the architecture can be found here:


> * ...
> Sorry, i had some more questions, but i just did fall asleep and
> cannot remember what else it was.
> thx in advance....
> Patrick Schwarck
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