[lustre-discuss] definition of a peer

[Faaland, Olaf P.]

Hi Amir,

Thanks for the explanation.  I noticed an address I didn't expect in a peer list, and so was trying to understand how it got there.  This helps.

It's no problem for me that peer blocks are persistent.  I saw that I can remove one for the case of those created by erroneous configurations, etc.

-Olaf

________________________________________
From: Amir Shehata <amir.shehata.whamcloud at gmail.com>
Sent: Thursday, August 27, 2020 9:12 AM
To: Faaland, Olaf P.
Cc: lustre-discuss at lists.lustre.org
Subject: Re: [lustre-discuss] definition of a peer

Hi Olaf,
A peer block on a local node is always created whenever you either try to communicate with it or it tries to communicate with you. So let's look at the active/passive cases

Active case
1. You try to send a message to <peer1-ip>@<net>
2. Lnet creates a peer block to identify that peer
3. OPTION 1: The message succeeds and you receive a response. Peer block remains.
4. OPTION 2: The message fails. Although you have not received a response that peer block remains

Passive case
1. You receive a message from <peer1-ip>@<net>
2. Lnet creates a peer block to identify that peer
3. OPTION 1: Response succeeds. peer block remains
4. OPTION 2: Response fails. In both 3&4 the peer block remains.

When you do a "lnetctl peer show" on the local net, what you're seeing is the set of peers since the startup of LNet which you either tried to communicate with or they tried to communicate with you, irregardless of success.

Question: Are you having problems with the fact that peers remain even after the physical node has gone away (or potentially peer blocks which have been created due to erroneous operations - bad config, etc)?

thanks
amir


On Wed, 26 Aug 2020 at 16:00, Faaland, Olaf P. <faaland1 at llnl.gov<mailto:faaland1 at llnl.gov>> wrote:
FWIW, I now think an lnet peer is just "a node I've communicated with at some time".

-Olaf

________________________________________
From: lustre-discuss <lustre-discuss-bounces at lists.lustre.org> on behalf of Faaland, Olaf P. <faaland1 at llnl.gov>
Sent: Wednesday, August 26, 2020 11:53 AM
To: lustre-discuss at lists.lustre.org
Subject: [lustre-discuss] definition of a peer

Hi All,

What is the definition of an lnet peer (in Lustre 2.12 and in master, if the definition has changed over time)?

I had believed it was a node that could be communicated with directly from LNet's perspective, e.g. without requiring transit through a lustre router.   But that seems not to be true on a node I'm looking at.

thanks,
-Olaf
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