[LU-14566] Skip discovery in LNetPrimaryNID when lnet_peer_discovery_disabled is set

• Type: Improvement
• Resolution: Fixed
• Priority: Minor
• Fix Version/s: Lustre 2.15.0
• Assignee: Chris Horn
• Reporter: Chris Horn

Description

If discovery is disabled locally then the discovery thread will not
modify any peer objects as a result of the discovery process. Thus,
the primary NID of any peer we're asked to discover will not change
as a result of discovery. Therefore, we do not need to actually
perform discovery in LNetPrimaryNID() if discovery is disabled
locally. Since this routine can result in long client mount times
when a Lustre server is down we should avoid this unnecessary
discovery.

Issue Links

• is related to: LU-14668 LNet: do discovery in the background

Comments

[Etienne Aujames]

We encountered an issue with 2 LNet routes missing on the server side (OSS): the clients could communicate with server but the servers could not answer.

Clients tried periodically to connect to the servers maintaining the missing peers in the discovery list (the_lnet.ln_dc_working). This have the consequences to wait indefinitely for peer discovery in ll_ostXX_XXX threads and progressively contaminating all the available threads (the client keep sending connection requests).

The server became unavailable for all the clients.

The "LNet discovery" and the "LNet health" is disabled on the clients and on the servers.

[Gerrit Updater]

Etienne AUJAMES ([e-mail]) uploaded a new patch: https://review.whamcloud.com/43537
Subject: LU-14566 lnet: Skip discovery in LNetPrimaryNID if DD disabled
Project: fs/lustre-release
Branch: b2_12
Current Patch Set: 1
Commit: 58cab53ba8c387722e638c097c0496af007f091f

[Peter Jones]

Landed for 2.15

[Gerrit Updater]

Oleg Drokin ([e-mail]) merged in patch https://review.whamcloud.com/43141/
Subject: LU-14566 lnet: Skip discovery in LNetPrimaryNID if DD disabled
Project: fs/lustre-release
Branch: master
Current Patch Set:
Commit: 16264da9e3c43a6368a25b6ded4113e8cfa57427

[Chris Horn]

That change will only impact local peers. Remote clients will still have to wait for the full lnet transaction timeout

[Amir Shehata (Inactive)]

Do you see this issue even with:

 LU-13972 o2iblnd: Don't retry indefinitely

?

[Gerrit Updater]

Chris Horn ([e-mail]) uploaded a new patch: https://review.whamcloud.com/43141
Subject: LU-14566 lnet: Skip discovery in LNetPrimaryNID if DD disabled
Project: fs/lustre-release
Branch: master
Current Patch Set: 1
Commit: eebda0deedd9a053f432b9638c70db2ce1cdf8ca