Re: Bug Found in Reef Releases - Action Required for pg-upmap-primary Interface Users

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How do you know if its safe to set `require-min-compat-client=reef` if you have kernel clients?

Thanks,
Kevin

________________________________________
From: Laura Flores <lflores@xxxxxxxxxx>
Sent: Wednesday, May 29, 2024 8:12 AM
To: ceph-users; dev; clt
Cc: Radoslaw Zarzynski; Yuri Weinstein
Subject:  Bug Found in Reef Releases - Action Required for pg-upmap-primary Interface Users

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Dear Ceph Users,

We have discovered a bug with the pg-upmap-primary interface (related to
the offline read balancer [1]) that affects all Reef releases.

In all Reef versions, users are required to set
`require-min-compat-client=reef` in order to use the pg-upmap-primary
interface to prevent pre-reef clients from connecting and not understanding
the new interface. We found this setting is simply not enforced [2], which
leads to miscommunication between older and newer peers or, depending on
version, to an assert in the mons and/or osds [3]. However, the fundamental
precondition is making use of the new `pg-upmap-primary` feature.

If you have not yet upgraded to v18.2.2, we recommend that you refrain from
upgrading to v18.2.2 until a later version is out with a fix. We also
recommend removing any existing pg-upmap-primary mappings to prevent
hitting the assert [3], as well as to prevent any miscommunication between
older and newer peers about pg primaries [2].
Remove mappings by:
$ `ceph osd dump`
For each pg_upmap_primary entry in the above output:
$ `ceph osd rm-pg-upmap-primary <pgid>`

If you have already upgraded to v18.2.2, your cluster is more likely to hit
the osd/mon assert [3] when you set a `pg-upmap-primary` mapping (this
would involve explicitly setting a mapping via the osdmaptool or the CLI
command). As long as you refrain from setting any pg-upmap-primary
mappings, your cluster will NOT be affected by [3].

Follow the trackers below for further updates.

1. pg-upmap-primary documentation:
https://docs.ceph.com/en/reef/rados/operations/read-balancer/
2. mon, osd, *: require-min-compat-client is not really honored -
https://tracker.ceph.com/issues/66260
3. Failed assert "pg_upmap_primaries.empty()" in the read balancer
 - https://tracker.ceph.com/issues/61948

Thanks,
Laura Flores

--

Laura Flores

She/Her/Hers

Software Engineer, Ceph Storage <https://ceph.io/>

Chicago, IL

lflores@xxxxxxx | lflores@xxxxxxxxxx <lflores@xxxxxxxxxx>
M: +17087388804
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