Clusterwide pids

[Greg Freemyer <freemyer-ml@NorcrossGroup.com>]

SInce this mailing list is dedicated to sharing cluster component technologies amongst the various Open Source cluster projects, Bruce Walker's comments got me thinking:



Definition:
CPID - Clusterwide Process ID.  Guaranteed to be unique for each process across the entire cluster.

(please advise if there is a pre-existing Acronym for this.)

Assumptions:
CPIDs are a useful concept and one that is used by several existing cluster solutions.

Sophisticated features, such as transparent clusterwide IPC, seem to require CPIDs

CPIDs may make process migration easier to implement. (I have no knowledge about this.)

For various reasons, implementing them seems difficult in a 16-bit pid world.

Changing pids to a 32-bit int will cause changes to the kernel and to many applications.  At a minimum many user level programs may need to be recompiled if this change were made.

Questions:
Given that CPIDs seem to be difficult to fully implement and involve the kernel, but if accomplished can be widely used throughout the OpenSource cluster projects, should a common CPID project be initiated?

Should CPIDs be added to Alan Robertson's infrastructure document as a future goal?  (Many HA clusters do not need CPIDs, so I would guess that it would not be appropriate, but I thought I would ask anyway.)

Bruce Walker relates that the SSI for Linux Clusters project has this working, and apparently PVM does as well.  Could either of these implementations, or some other existing implementation, be isolated and made available to the Linux Cluster community as a component?

Can the CPID module be written in such a way as to allow multiple cluster membership algorithms?

If so, what are the chances of this component being made a part of the standard Linux kernel?  I realize many people are against significant changes to the kernel, but I do not see a way for CPIDs to be implemented outside of the kernel, and one common solution seems far better than a separate solution for each Cluster Solution which needs CPIDs.


Greg Freemyer
Internet Engineer
Deployment and Integration Specialist
The Norcross Group
www.NorcrossGroup.com


>>  Annon wrote:
>>  > 
>>  > MOSIX indeed has a unique node #, but still uses only 16-bit PIDs
>>  > in order to avoid any changes to the user-level interface.
>>  > As a result, PIDs are NOT unique across the cluster.
>>  > 
>>  > Amnon Shiloh -- the HUJI MOSIX group.

>>  The SSI project that was recently launched 
>>  (you can find it from www.opensource.compaq.com) has
>>  unique node numbers, 32-bit pids on 32 bit hardware and
>>  clusterwide unique pids (the technology base the
>>  SSI project is seeded with has had clusterwide unique
>>  pids and process migration for over 15 years and a 
>>  single clusterwide root filesystem for over 20 years
>>  (Locus technology, TCF, TNC, and NonStop Clusters for Unixware).

>>  A first developer release, including:
>>  - cluster membership and internode communication from
>>      the Cluster Infrastructure project
>>  - capability for clusters up to 64 nodes
>>  - clusterwide root filesystem
>>  - clusterwide process ids and access to all
>>      processes from all nodes at all times
>>  - full SSI remote exec, inheriting pid, open files,
>>      open sockets, open pipes, open devices, etc.
>>  - process migration, if we finish the port in time
>>  - clusterwide device naming and access
>>  - clusterwide message queue naming and access
>>  - clusterwide fifo naming and access
>>  - single init for the cluster, with support to have
>>      the cluster at different run levels
>>  - no single points of failure for the cluster
>>  - application monitoring and failover
>>  should be out this month.

>>  Please come and join the project (at least via the email 
>>  list for now).

>>  bruce.walker@compaq.com
>>  Open SSI Cluster architect
>>  Compaq.



>>  > 
>>  > Linux-cluster: generic cluster infrastructure for Linux
>>  > Archive:       http://mail.nl.linux.org/linux-cluster/


>>  Linux-cluster: generic cluster infrastructure for Linux
>>  Archive:       http://mail.nl.linux.org/linux-cluster/








Linux-cluster: generic cluster infrastructure for Linux
Archive:       http://mail.nl.linux.org/linux-cluster/