Okay, well that will be the same reason then. If the active MDS is
connected to a monitor and they fail at the same time, the monitors can’t
replace the mds until they’ve been through their own election and a full
mds timeout window.
On Thu, Aug 30, 2018 at 11:46 AM William Lawton <william.law...@irdeto.com>
wrote:
> Thanks for the response Greg. We did originally have co-located mds and
> mon but realised this wasn't a good idea early on and separated them out
> onto different hosts. So our mds hosts are on ceph-01 and ceph-02, and our
> mon hosts are on ceph-03, 04 and 05. Unfortunately we see this issue
> occurring when we reboot ceph-02(mds) and ceph-04(mon) together. We expect
> ceph-01 to become the active mds but often it doesnt.
>
> Sent from my iPhone
>
> On 30 Aug 2018, at 17:46, Gregory Farnum <gfar...@redhat.com> wrote:
>
> Yes, this is a consequence of co-locating the MDS and monitors — if the
> MDS reports to its co-located monitor and both fail, the monitor cluster
> has to go through its own failure detection and then wait for a full MDS
> timeout period after that before it marks the MDS down. :(
>
> We might conceivably be able to optimize for this, but there's not a
> general solution. If you need to co-locate, one thing that would make it
> better without being a lot of work is trying to have the MDS connect to one
> of the monitors on a different host. You can do that by just restricting
> the list of monitors you feed it in the ceph.conf, although it's not a
> guarantee that will *prevent* it from connecting to its own monitor if
> there are failures or reconnects after first startup.
> -Greg
>
> On Thu, Aug 30, 2018 at 8:38 AM William Lawton <william.law...@irdeto.com>
> wrote:
>
>> Hi.
>>
>>
>>
>> We have a 5 node Ceph cluster (refer to ceph -s output at bottom of
>> email). During resiliency tests we have an occasional problem when we
>> reboot the active MDS instance and a MON instance together i.e.
>> dub-sitv-ceph-02 and dub-sitv-ceph-04. We expect the MDS to failover to
>> the standby instance dub-sitv-ceph-01 which is in standby-replay mode, and
>> 80% of the time it does with no problems. However, 20% of the time it
>> doesn’t and the MDS_ALL_DOWN health check is not cleared until 30 seconds
>> later when the rebooted dub-sitv-ceph-02 and dub-sitv-ceph-04 instances
>> come back up.
>>
>>
>>
>> When the MDS successfully fails over to the standby we see in the
>> ceph.log the following:
>>
>>
>>
>> 2018-08-25 00:30:02.231811 mon.dub-sitv-ceph-03 mon.0 10.18.53.32:6789/0
>> 50 : cluster [ERR] Health check failed: 1 filesystem is offline
>> (MDS_ALL_DOWN)
>>
>> 2018-08-25 00:30:02.237389 mon.dub-sitv-ceph-03 mon.0 10.18.53.32:6789/0
>> 52 : cluster [INF] Standby daemon mds.dub-sitv-ceph-01 assigned to
>> filesystem cephfs as rank 0
>>
>> 2018-08-25 00:30:02.237528 mon.dub-sitv-ceph-03 mon.0 10.18.53.32:6789/0
>> 54 : cluster [INF] Health check cleared: MDS_ALL_DOWN (was: 1 filesystem is
>> offline)
>>
>>
>>
>> When the active MDS role does not failover to the standby the
>> MDS_ALL_DOWN check is not cleared until after the rebooted instances have
>> come back up e.g.:
>>
>>
>>
>> 2018-08-25 03:30:02.936554 mon.dub-sitv-ceph-03 mon.0 10.18.53.32:6789/0
>> 55 : cluster [ERR] Health check failed: 1 filesystem is offline
>> (MDS_ALL_DOWN)
>>
>> 2018-08-25 03:30:04.235703 mon.dub-sitv-ceph-05 mon.2
>> 10.18.186.208:6789/0 226 : cluster [INF] mon.dub-sitv-ceph-05 calling
>> monitor election
>>
>> 2018-08-25 03:30:04.238672 mon.dub-sitv-ceph-03 mon.0 10.18.53.32:6789/0
>> 56 : cluster [INF] mon.dub-sitv-ceph-03 calling monitor election
>>
>> 2018-08-25 03:30:09.242595 mon.dub-sitv-ceph-03 mon.0 10.18.53.32:6789/0
>> 57 : cluster [INF] mon.dub-sitv-ceph-03 is new leader, mons
>> dub-sitv-ceph-03,dub-sitv-ceph-05 in quorum (ranks 0,2)
>>
>> 2018-08-25 03:30:09.252804 mon.dub-sitv-ceph-03 mon.0 10.18.53.32:6789/0
>> 62 : cluster [WRN] Health check failed: 1/3 mons down, quorum
>> dub-sitv-ceph-03,dub-sitv-ceph-05 (MON_DOWN)
>>
>> 2018-08-25 03:30:09.258693 mon.dub-sitv-ceph-03 mon.0 10.18.53.32:6789/0
>> 63 : cluster [WRN] overall HEALTH_WARN 2 osds down; 2 hosts (2 osds) down;
>> 1/3 mons down, quorum dub-sitv-ceph-03,dub-sitv-ceph-05
>>
>> 2018-08-25 03:30:10.254162 mon.dub-sitv-ceph-03 mon.0 10.18.53.32:6789/0
>> 64 : cluster [WRN] Health check failed: Reduced data availability: 2 pgs
>> inactive, 115 pgs peering (PG_AVAILABILITY)
>>
>> 2018-08-25 03:30:12.429145 mon.dub-sitv-ceph-03 mon.0 10.18.53.32:6789/0
>> 66 : cluster [WRN] Health check failed: Degraded data redundancy: 712/2504
>> objects degraded (28.435%), 86 pgs degraded (PG_DEGRADED)
>>
>> 2018-08-25 03:30:16.137408 mon.dub-sitv-ceph-03 mon.0 10.18.53.32:6789/0
>> 67 : cluster [WRN] Health check update: Reduced data availability: 1 pg
>> inactive, 69 pgs peering (PG_AVAILABILITY)
>>
>> 2018-08-25 03:30:17.193322 mon.dub-sitv-ceph-03 mon.0 10.18.53.32:6789/0
>> 68 : cluster [INF] Health check cleared: PG_AVAILABILITY (was: Reduced data
>> availability: 1 pg inactive, 69 pgs peering)
>>
>> 2018-08-25 03:30:18.432043 mon.dub-sitv-ceph-03 mon.0 10.18.53.32:6789/0
>> 69 : cluster [WRN] Health check update: Degraded data redundancy: 1286/2572
>> objects degraded (50.000%), 166 pgs degraded (PG_DEGRADED)
>>
>> 2018-08-25 03:30:26.139491 mon.dub-sitv-ceph-03 mon.0 10.18.53.32:6789/0
>> 71 : cluster [WRN] Health check update: Degraded data redundancy: 1292/2584
>> objects degraded (50.000%), 166 pgs degraded (PG_DEGRADED)
>>
>> 2018-08-25 03:30:31.355321 mon.dub-sitv-ceph-04 mon.1 10.18.53.155:6789/0
>> 1 : cluster [INF] mon.dub-sitv-ceph-04 calling monitor election
>>
>> 2018-08-25 03:30:31.371519 mon.dub-sitv-ceph-04 mon.1 10.18.53.155:6789/0
>> 2 : cluster [WRN] message from mon.0 was stamped 0.817433s in the future,
>> clocks not synchronized
>>
>> 2018-08-25 03:30:32.175677 mon.dub-sitv-ceph-03 mon.0 10.18.53.32:6789/0
>> 72 : cluster [INF] mon.dub-sitv-ceph-03 calling monitor election
>>
>> 2018-08-25 03:30:32.175864 mon.dub-sitv-ceph-05 mon.2
>> 10.18.186.208:6789/0 227 : cluster [INF] mon.dub-sitv-ceph-05 calling
>> monitor election
>>
>> 2018-08-25 03:30:32.180615 mon.dub-sitv-ceph-03 mon.0 10.18.53.32:6789/0
>> 73 : cluster [INF] mon.dub-sitv-ceph-03 is new leader, mons
>> dub-sitv-ceph-03,dub-sitv-ceph-04,dub-sitv-ceph-05 in quorum (ranks 0,1,2)
>>
>> 2018-08-25 03:30:32.189593 mon.dub-sitv-ceph-03 mon.0 10.18.53.32:6789/0
>> 78 : cluster [INF] Health check cleared: MON_DOWN (was: 1/3 mons down,
>> quorum dub-sitv-ceph-03,dub-sitv-ceph-05)
>>
>> 2018-08-25 03:30:32.190820 mon.dub-sitv-ceph-03 mon.0 10.18.53.32:6789/0
>> 79 : cluster [WRN] mon.1 10.18.53.155:6789/0 clock skew 0.811318s > max
>> 0.05s
>>
>> 2018-08-25 03:30:32.194280 mon.dub-sitv-ceph-03 mon.0 10.18.53.32:6789/0
>> 80 : cluster [WRN] overall HEALTH_WARN 2 osds down; 2 hosts (2 osds) down;
>> Degraded data redundancy: 1292/2584 objects degraded (50.000%), 166 pgs
>> degraded
>>
>> 2018-08-25 03:30:35.076121 mon.dub-sitv-ceph-03 mon.0 10.18.53.32:6789/0
>> 83 : cluster [INF] daemon mds.dub-sitv-ceph-02 restarted
>>
>> 2018-08-25 03:30:35.270222 mon.dub-sitv-ceph-03 mon.0 10.18.53.32:6789/0
>> 85 : cluster [WRN] Health check failed: 1 filesystem is degraded
>> (FS_DEGRADED)
>>
>> 2018-08-25 03:30:35.270267 mon.dub-sitv-ceph-03 mon.0 10.18.53.32:6789/0
>> 86 : cluster [ERR] Health check failed: 1 filesystem is offline
>> (MDS_ALL_DOWN)
>>
>> 2018-08-25 03:30:35.282139 mon.dub-sitv-ceph-03 mon.0 10.18.53.32:6789/0
>> 88 : cluster [INF] Standby daemon mds.dub-sitv-ceph-01 assigned to
>> filesystem cephfs as rank 0
>>
>> 2018-08-25 03:30:35.282268 mon.dub-sitv-ceph-03 mon.0 10.18.53.32:6789/0
>> 89 : cluster [INF] Health check cleared: MDS_ALL_DOWN (was: 1 filesystem is
>> offline)
>>
>>
>>
>> In the MDS log we’ve noticed that when the issue occurs, at precisely the
>> time when the active MDS/MON nodes are rebooted, the standby MDS instance
>> briefly stops logging replay_done (as standby). This is shown in the log
>> exert below where there is a 9s gap in these logs.
>>
>>
>>
>> 2018-08-25 03:30:00.085 7f3ab9b00700 1 mds.0.0 replay_done (as standby)
>>
>> 2018-08-25 03:30:01.091 7f3ab9b00700 1 mds.0.0 replay_done (as standby)
>>
>> 2018-08-25 03:30:10.332 7f3ab9b00700 1 mds.0.0 replay_done (as standby)
>>
>> 2018-08-25 03:30:11.333 7f3abb303700 1 mds.0.0 replay_done (as standby)
>>
>>
>>
>> I’ve tried to reproduce the issue by rebooting each MDS instance in turn
>> repeatedly 5 minutes apart but so far haven’t been able to do so, so my
>> assumption is that rebooting the MDS and a MON instance at the same time is
>> a significant factor.
>>
>>
>>
>> Our mds_standby* configuration is set as follows:
>>
>>
>>
>> "mon_force_standby_active": "true",
>>
>> "mds_standby_for_fscid": "-1",
>>
>> "mds_standby_for_name": "",
>>
>> "mds_standby_for_rank": "0",
>>
>> "mds_standby_replay": "true",
>>
>>
>>
>> The cluster status is as follows:
>>
>>
>>
>> cluster:
>>
>> id: f774b9b2-d514-40d9-85ab-d0389724b6c0
>>
>> health: HEALTH_OK
>>
>>
>>
>> services:
>>
>> mon: 3 daemons, quorum
>> dub-sitv-ceph-03,dub-sitv-ceph-04,dub-sitv-ceph-05
>>
>> mgr: dub-sitv-ceph-04(active), standbys: dub-sitv-ceph-03,
>> dub-sitv-ceph-05
>>
>> mds: cephfs-1/1/1 up {0=dub-sitv-ceph-02=up:active}, 1
>> up:standby-replay
>>
>> osd: 4 osds: 4 up, 4 in
>>
>>
>>
>> data:
>>
>> pools: 2 pools, 200 pgs
>>
>> objects: 554 objects, 980 MiB
>>
>> usage: 7.9 GiB used, 1.9 TiB / 2.0 TiB avail
>>
>> pgs: 200 active+clean
>>
>>
>>
>> io:
>>
>> client: 1.5 MiB/s rd, 810 KiB/s wr, 286 op/s rd, 218 op/s wr
>>
>>
>>
>> Hope someone can help!
>>
>> *William Lawton*
>>
>>
>> _______________________________________________
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>> ceph-users@lists.ceph.com
>> http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
>>
>
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