[lustre-discuss] definition of a peer

[Amir Shehata]

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> 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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