Am 15.04.2018 um 23:04 schrieb John Spray:
> On Fri, Apr 13, 2018 at 5:16 PM, Oliver Freyermuth
> <freyermuth@xxxxxxxxxxxxxxxxxx> wrote:
>> Dear Cephalopodians,
>>
>> in our cluster (CentOS 7.4, EC Pool, Snappy compression, Luminous 12.2.4),
>> we often have all (~40) clients accessing one file in readonly mode, even with multiple processes per client doing that.
>>
>> Sometimes (I do not yet know when, nor why!) the MDS ends up in a situation like:
>> -----------------------------------------------------------
>> 2018-04-13 18:08:34.378888 7f1ce4472700 0 log_channel(cluster) log [WRN] : 292 slow requests, 5 included below; oldest blocked for > 1745.864417 secs
>> 2018-04-13 18:08:34.378900 7f1ce4472700 0 log_channel(cluster) log [WRN] : slow request 960.563534 seconds old, received at 2018-04-13 17:52:33.815273: client_request(client.34720:16487379 getattr pAsLsXsFs #0x1000009ff6d 2018-04-13 17:52:33.814904 caller_uid=94894, caller_gid=513{513,}) currently failed to rdlock, waiting
>> 2018-04-13 18:08:34.378904 7f1ce4472700 0 log_channel(cluster) log [WRN] : slow request 30.636678 seconds old, received at 2018-04-13 18:08:03.742128: client_request(client.34302:16453640 getattr pAsLsXsFs #0x1000009ff6d 2018-04-13 18:08:03.741630 caller_uid=94894, caller_gid=513{513,}) currently failed to rdlock, waiting
>> 2018-04-13 18:08:34.378908 7f1ce4472700 0 log_channel(cluster) log [WRN] : slow request 972.648926 seconds old, received at 2018-04-13 17:52:21.729881: client_request(client.34720:16487334 lookup #0x1000001fcab/sometarball.tar.gz 2018-04-13 17:52:21.729450 caller_uid=94894, caller_gid=513{513,}) currently failed to rdlock, waiting
>> 2018-04-13 18:08:34.378913 7f1ce4472700 0 log_channel(cluster) log [WRN] : slow request 1685.953657 seconds old, received at 2018-04-13 17:40:28.425149: client_request(client.34810:16564864 lookup #0x1000001fcab/sometarball.tar.gz 2018-04-13 17:40:28.424961 caller_uid=94894, caller_gid=513{513,}) currently failed to rdlock, waiting
>> 2018-04-13 18:08:34.378918 7f1ce4472700 0 log_channel(cluster) log [WRN] : slow request 1552.743795 seconds old, received at 2018-04-13 17:42:41.635012: client_request(client.34302:16453566 getattr pAsLsXsFs #0x1000009ff6d 2018-04-13 17:42:41.634726 caller_uid=94894, caller_gid=513{513,}) currently failed to rdlock, waiting
>> -----------------------------------------------------------
>> As you can see (oldest blocked for > 1745.864417 secs) it stays in that situation for quite a while.
>> The number of blocked requests is also not decreasing, but instead slowly increasing whenever a new request is added to the queue.
>>
>> We have a setup of one active MDS, a standby-replay, and a standby.
>> Triggering a failover does not help, it only resets the "oldest blocked" time.
>
> Sounds like a client issue (a client is holding a lock on a file but
> failing to relinquish it for another client's request to be
> processed).
>
> Are these kernel (and what version?) or fuse clients?
The full cluster is running with Fuse clients, all on 12.2.4.
Additionally, there are 6 NFS Ganesha servers using FSAL_CEPH, i.e. libcephfs.
Cheers,
Oliver
>
> John
>
>>
>> I checked the following things on the active MDS:
>> -----------------------------------------------------------
>> # ceph daemon mds.mon001 objecter_requests
>> {
>> "ops": [],
>> "linger_ops": [],
>> "pool_ops": [],
>> "pool_stat_ops": [],
>> "statfs_ops": [],
>> "command_ops": []
>> }
>> # ceph daemon mds.mon001 ops | grep event | grep -v "initiated" | grep -v "failed to rdlock" | grep -v events
>> => no output, only "initiated" and "rdlock" are in the queue.
>> -----------------------------------------------------------
>>
>> There's also almost no CPU load, almost no other I/O, and ceph is deep-scrubbing ~pg (this also finishes and the next pg is scrubbed fine),
>> and the scrubbing is not even happening in the metadata pool (easy to see in the Luminous dashboard):
>> -----------------------------------------------------------
>> # ceph -s
>> cluster:
>> id: some_funny_hash
>> health: HEALTH_WARN
>> 1 MDSs report slow requests
>>
>> services:
>> mon: 3 daemons, quorum mon003,mon001,mon002
>> mgr: mon001(active), standbys: mon002, mon003
>> mds: cephfs_baf-1/1/1 up {0=mon001=up:active}, 1 up:standby-replay, 1 up:standby
>> osd: 196 osds: 196 up, 196 in
>>
>> data:
>> pools: 2 pools, 4224 pgs
>> objects: 15649k objects, 61761 GB
>> usage: 114 TB used, 586 TB / 700 TB avail
>> pgs: 4223 active+clean
>> 1 active+clean+scrubbing+deep
>>
>> io:
>> client: 175 kB/s rd, 3 op/s rd, 0 op/s wr
>> -----------------------------------------------------------
>>
>> Does anybody have any idea what's going on here?
>>
>> Yesterday, this also happened, but resolved itself after about 1 hour.
>> Right now, it's going on for about half an hour...
>>
>> Cheers,
>> Oliver
>>
>>
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>>
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