Hello all! Hope that anybody can help us.

The initial point:  Ceph cluster v15.2 (installed and controlled by the 
Proxmox) with 3 nodes based on physical servers rented from a cloud provider. 
The volumes provided by Ceph using CephFS and RBD also. We run 2 MDS daemons 
but use max_mds=1 so one daemon was in active state, and another in standby.
On Thursday some of the applications stopped working. After the investigation 
it was clear that we have a problem with Ceph, more precisely with СephFS - 
both MDS daemons suddenly crashed. We tried to restart them and found that they 
crashed again immediately after the start. The crash information:

2024-04-17T17:47:42.841+0000 7f959ced9700  1 mds.0.29134 recovery_done -- 
successful recovery!
2024-04-17T17:47:42.853+0000 7f959ced9700  1 mds.0.29134 active_start
2024-04-17T17:47:42.881+0000 7f959ced9700  1 mds.0.29134 cluster recovered.
2024-04-17T17:47:43.825+0000 7f959aed5700 -1 ./src/mds/OpenFileTable.cc: In 
function 'void OpenFileTable::commit(MDSContext*, uint64_t, int)' thread 
7f959aed5700 time 2024-04-17T17:47:43.831243+0000
./src/mds/OpenFileTable.cc: 549: FAILED ceph_assert(count > 0)

Next hours we read tons of articles, studied the documentation, and checked the 
cluster status in general by the various diagnostic commands - but didn't find 
anything wrong. At evening we decided to upgrade our Ceph cluster; so, we 
upgraded it to v16, and finally to v17.2.7. Unfortunately, it didn't solve the 
problem, MDS continue to crash with the same error. The only difference that we 
found is the "1 MDSs report damaged metadata" in the output of ceph -s - see it 
below.

I supposed that it may be the well-known bug, but couldn't find the same one on 
https://tracker.ceph.com - there are several bugs associated with file 
OpenFileTable.cc but not related to ceph_assert(count > 0)
We tried to check the source code of OpenFileTable.cc also, here is a fragment 
of it, in function OpenFileTable::_journal_finish
      int omap_idx = anchor.omap_idx;
      unsigned& count = omap_num_items.at(omap_idx);
      ceph_assert(count > 0);

So, we guess that the object map is empty for some object in Ceph, and it is 
unexpected behavior. But again, we found nothing wrong in our cluster...

Next, we started with 
https://docs.ceph.com/en/latest/cephfs/disaster-recovery-experts/ article - 
tried to reset the journal (despite that it was Ok all the time) and wipe the 
sessions using cephfs-table-tool all reset session command. No result...
Now I decided to continue following this article and run cephfs-data-scan 
scan_extents command, we started it on Friday but it is still working (2 from 3 
workers finished, so I'm waiting for the last one; may be I need more workers 
for the next command cephfs-data-scan scan_inodes that I plan to run ). But I 
have a doubt that it will solve the issue because, again, we guess that we have 
no problem with our objects in Ceph but with metadata only...

Is it the new bug? or something else? What should we try additionally to run 
our MDS daemon? Any idea is welcome!

The important outputs:
ceph -s
  cluster:
    id:     4cd1c477-c8d0-4855-a1f1-cb71d89427ed
    health: HEALTH_ERR
            1 MDSs report damaged metadata
            insufficient standby MDS daemons available
            83 daemons have recently crashed
            3 mgr modules have recently crashed

  services:
    mon: 3 daemons, quorum asrv-dev-stor-2,asrv-dev-stor-3,asrv-dev-stor-1 (age 
22h)
    mgr: asrv-dev-stor-2(active, since 22h), standbys: asrv-dev-stor-1
    mds: 1/1 daemons up
    osd: 18 osds: 18 up (since 22h), 18 in (since 29h)

  data:
    volumes: 1/1 healthy
    pools:   5 pools, 289 pgs
    objects: 29.72M objects, 5.6 TiB
    usage:   21 TiB used, 47 TiB / 68 TiB avail
    pgs:     287 active+clean
             2   active+clean+scrubbing+deep

  io:
    client:   2.5 KiB/s rd, 172 KiB/s wr, 261 op/s rd, 195 op/s wr

ceph fs dump
e29480
enable_multiple, ever_enabled_multiple: 0,1
default compat: compat={},rocompat={},incompat={1=base v0.20,2=client writeable 
ranges,3=default file layouts on dirs,4=dir inode in separate object,5=mds uses 
versioned encoding,6=dirfrag is stored in omap,7=mds uses inline data,8=no 
anchor table,9=file layout v2,10=snaprealm v2}
legacy client fscid: 1

Filesystem 'cephfs' (1)
fs_name cephfs
epoch   29480
flags   12 joinable allow_snaps allow_multimds_snaps
created 2022-11-25T15:56:08.507407+0000
modified        2024-04-18T16:52:29.970504+0000
tableserver     0
root    0
session_timeout 60
session_autoclose       300
max_file_size   1099511627776
required_client_features        {}
last_failure    0
last_failure_osd_epoch  14728
compat  compat={},rocompat={},incompat={1=base v0.20,2=client writeable 
ranges,3=default file layouts on dirs,4=dir inode in separate object,5=mds uses 
versioned encoding,6=dirfrag is stored in omap,7=mds uses inline data,8=no 
anchor table,9=file layout v2,10=snaprealm v2}
max_mds 1
in      0
up      {0=156636152}
failed
damaged
stopped
data_pools      [5]
metadata_pool   6
inline_data     disabled
balancer
standby_count_wanted    1
[mds.asrv-dev-stor-1{0:156636152} state up:active seq 6 laggy since 
2024-04-18T16:52:29.970479+0000 addr 
[v2:172.22.2.91:6800/2487054023,v1:172.22.2.91:6801/2487054023] compat 
{c=[1],r=[1],i=[7ff]}]

cephfs-journal-tool --rank=cephfs:0 journal inspect
Overall journal integrity: OK

ceph pg dump summary
version 41137
stamp 2024-04-18T21:17:59.133536+0000
last_osdmap_epoch 0
last_pg_scan 0
PG_STAT  OBJECTS   MISSING_ON_PRIMARY  DEGRADED  MISPLACED  UNFOUND  BYTES      
    OMAP_BYTES*  OMAP_KEYS*  LOG      DISK_LOG
sum      29717605                   0         0          0        0  
6112544251872  13374192956    28493480  1806575   1806575
OSD_STAT  USED    AVAIL   USED_RAW  TOTAL
sum       21 TiB  47 TiB    21 TiB  68 TiB

ceph pg dump pools
POOLID  OBJECTS   MISSING_ON_PRIMARY  DEGRADED  MISPLACED  UNFOUND  BYTES       
   OMAP_BYTES*  OMAP_KEYS*  LOG     DISK_LOG
8          31771                   0         0          0        0   
131337887503         2482         140  401246    401246
7         839707                   0         0          0        0  
3519034650971          736          61  399328    399328
6        1319576                   0         0          0        0      
421044421  13374189738    28493279  206749    206749
5       27526539                   0         0          0        0  
2461702171417            0           0  792165    792165
2             12                   0         0          0        0       
48497560            0           0    6991      6991


---
Best regards,

Alexey Gerasimov
System Manager

www.opencascade.com<http://www.opencascade.com/>
www.capgemini.com<http://www.capgemini.com>

[cid:image001.png@01DA93D0.B001CE80]

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