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Re: [Cluster-devel] RFC: generic improvement to fence agents api



Hi,

On 03/19/2011 07:34 AM, Fabio M. Di Nitto wrote:
    <device name="..." ports="1 2"/>
....

Either by using a new keyword "ports" or re-using "port" itself. If
using "port", current configuration will continue to work as-is and the
change effectively would not introduce any backward compatibility issue.

This way the agent can:

1) connect once (reducing in most cases the ssh/telnet/whatever time)
2) issue the OFF command as fast as possible (almost in parallel)
3) then wait for the results.

By adopting a list, the configuration would look cleaner too IMHO.

A quick glance, the change should not affect fenced (David can you
confirm please?), and most agents could handle it via the fencing python
lib (Marek?).

1) connect once will work only for connection-based fence agents. It won't help with SNMP + HTTP REST and there won't be any benefits for drac/ilo/ipmi that can turn off only one machine. Rough estimate is that it can help us to improve time in 1/3 to 1/2 fence agents.

2) parallelism is possible only on those fence devices that works in async mode. Issuing more than one command will also increase a need for QE. Some of those devices are not able even to handle 'get status' immediately after 'power off' (reason for --power-wait). Serialization within same connection is definitely possible and for fencing python lib we can implement that directly in library.

-) "ports" is better than "port" because such change will have impact also on UI and we have to distinguish if fence agent accept more than one port or not.

-) There is no character that can't be used for name of virtual machine.

m,



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