Re: cluster unavailable for 20 mins when downed server was reintroduced

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On Tue, 15 Aug 2017, Gregory Farnum said:
> On Tue, Aug 15, 2017 at 4:23 AM Sean Purdy <s.purdy@xxxxxxxxxxxxxxxx> wrote:
> > I have a three node cluster with 6 OSD and 1 mon per node.
> >
> > I had to turn off one node for rack reasons.  While the node was down, the
> > cluster was still running and accepting files via radosgw.  However, when I
> > turned the machine back on, radosgw uploads stopped working and things like
> > "ceph status" starting timed out.  It took 20 minutes for "ceph status" to
> > be OK.

> > 2017-08-15 11:28:29.835943 7fdf2d74b700  0 monclient(hunting):
> > authenticate timed out after 300                        2017-08-15
> > 11:28:29.835993 7fdf2d74b700  0 librados: client.admin authentication error
> > (110) Connection timed out
> >
> 
> That just means the client couldn't connect to an in-quorum monitor. It
> should have tried them all in sequence though — did you check if you had
> *any* functioning quorum?

There was a functioning quorum - I checked with "ceph --admin-daemon /var/run/ceph/ceph-mon.xxx.asok quorum_status".  Well - I interpreted the output as functioning.  There was a nominated leader.
 

> > 2017-08-15 11:23:07.180123 7f11c0fcc700  0 -- 172.16.0.43:0/2471 >>
> > 172.16.0.45:6812/1904 conn(0x556eeaf4d000 :-1
> > s=STATE_CONNECTING_WAIT_CONNECT_REPLY_AUTH pgs=0 cs=0
> > l=0).handle_connect_reply connect got BADAUTHORIZER
> >
> 
> This one's odd. We did get one report of seeing something like that, but I
> tend to think it's a clock sync issue.

I saw some messages about clock sync, but ntpq -p looked OK on each server.  Will investigate further.

     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
+172.16.0.16     129.250.35.250   3 u  847 1024  377    0.289    1.103   0.376
+172.16.0.18     80.82.244.120    3 u   93 1024  377    0.397   -0.653   1.040
*172.16.0.19     158.43.128.33    2 u  279 1024  377    0.244    0.262   0.158
 

> > ERROR: unable to open OSD superblock on /var/lib/ceph/osd/ceph-9: (2) No
> > such file or directory
> >
> And that would appear to be something happening underneath Ceph, wherein
> your data wasn't actually all the way mounted or something?

It's the machine mounting the disks at boot time - udev or ceph-osd.target keeps retrying until eventually the disk/OSD is mounted.  Or eventually it gives up.  Do the OSDs need a monitor quorum at startup?  It kept restarting OSDs for 20 mins.

Timing went like this:

11:22 node boot
11:22 ceph-mon starts, recovers logs, compaction, first BADAUTHORIZER message
11:22 starting disk activation for 18 partitions (3 per bluestore)
11:23 mgr on other node can't find secret_id
11:43 bluefs mount succeeded on OSDs, ceph-osds go live
11:45 last BADAUTHORIZER message in monitor log
11:45 this host calls and wins a monitor election, mon_down health check clears
11:45 mgr happy
 
 
> Anyway, it should have survived that transition without any noticeable
> impact (unless you are running so close to capacity that merely getting the
> downed node up-to-date overwhelmed your disks/cpu). But without some basic
> information about what the cluster as a whole was doing I couldn't
> speculate.

This is a brand new 3 node cluster.  Dell R720 running Debian 9 with 2x SSD for OS and ceph-mon, 6x 2Tb SATA for ceph-osd using bluestore, per node.  Running radosgw as object store layer.  Only activity is a single-threaded test job uploading millions of small files over S3.  There are about 5.5million test objects so far (additionally 3x replication).  This job was fine when the machine was down, stalled when machine booted.

Looking at activity graphs at the time, there didn't seem to be a network bottleneck or CPU issue or disk throughput bottleneck.  But I'll look a bit closer.

ceph-mon is on an ext4 filesystem though.   Perhaps I should move this to xfs?  Bluestore is xfs+bluestore.

I presume it's a monitor issue somehow.


> -Greg

Thanks for your input.

Sean
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