On Wed, Jun 1, 2016 at 10:22 PM, Sage Weil <sage@xxxxxxxxxxxx> wrote:
> On Wed, 1 Jun 2016, Yan, Zheng wrote:
>> On Wed, Jun 1, 2016 at 8:49 PM, Sage Weil <sage@xxxxxxxxxxxx> wrote:
>> > On Wed, 1 Jun 2016, Yan, Zheng wrote:
>> >> On Wed, Jun 1, 2016 at 6:15 AM, James Webb <jamesw@xxxxxxxxxxx> wrote:
>> >> > Dear ceph-users...
>> >> >
>> >> > My team runs an internal buildfarm using ceph as a backend storage platform. We’ve recently upgraded to Jewel and are having reliability issues that we need some help with.
>> >> >
>> >> > Our infrastructure is the following:
>> >> > - We use CEPH/CEPHFS (10.2.1)
>> >> > - We have 3 mons and 6 storage servers with a total of 36 OSDs (~4160 PGs).
>> >> > - We use enterprise SSDs for everything including journals
>> >> > - We have one main mds and one standby mds.
>> >> > - We are using ceph kernel client to mount cephfs.
>> >> > - We have upgrade to Ubuntu 16.04 (4.4.0-22-generic kernel)
>> >> > - We are using a kernel NFS to serve NFS clients from a ceph mount (~ 32 nfs threads. 0 swappiness)
>> >> > - These are physical machines with 8 cores & 32GB memory
>> >> >
>> >> > On a regular basis, we lose all IO via ceph FS. We’re still trying to isolate the issue but it surfaces as an issue between MDS and ceph client.
>> >> > We can’t tell if our our NFS server is overwhelming the MDS or if this is some unrelated issue. Tuning NFS server has not solved our issues.
>> >> > So far our only recovery has been to fail the MDS and then restart our NFS. Any help or advice will be appreciated on the CEPH side of things.
>> >> > I’m pretty sure we’re running with default tuning of CEPH MDS configuration parameters.
>> >> >
>> >> >
>> >> > Here are the relevant log entries.
>> >> >
>> >> > From my primary MDS server, I start seeing these entries start to pile up:
>> >> >
>> >> > 2016-05-31 14:34:07.091117 7f9f2eb87700 0 log_channel(cluster) log [WRN] : client.4283066 isn't responding to mclientcaps(revoke), ino 10000004491 pending pAsLsXsFsxcrwb issued pAsxLsXsxFsxcrwb, sent 63.877480 seconds ago\
>> >> > 2016-05-31 14:34:07.091129 7f9f2eb87700 0 log_channel(cluster) log [WRN] : client.4283066 isn't responding to mclientcaps(revoke), ino 10000005ddf pending pAsLsXsFsxcrwb issued pAsxLsXsxFsxcrwb, sent 63.877382 seconds ago\
>> >> > 2016-05-31 14:34:07.091133 7f9f2eb87700 0 log_channel(cluster) log [WRN] : client.4283066 isn't responding to mclientcaps(revoke), ino 10000000a2a pending pAsLsXsFsxcrwb issued pAsxLsXsxFsxcrwb, sent 63.877356 seconds ago
>> >> >
>> >> > From my NFS server, I see these entries from dmesg also start piling up:
>> >> > [Tue May 31 14:33:09 2016] libceph: skipping mds0 X.X.X.195:6800 seq 0 expected 4294967296
>> >> > [Tue May 31 14:33:09 2016] libceph: skipping mds0 X.X.X.195:6800 seq 1 expected 4294967296
>> >> > [Tue May 31 14:33:09 2016] libceph: skipping mds0 X.X.X.195:6800 seq 2 expected 4294967296
>> >> >
>> >>
>> >> 4294967296 is 0x100000000, this looks like sequence overflow.
>> >>
>> >> In src/msg/Message.h:
>> >>
>> >> class Message {
>> >> ...
>> >> unsigned get_seq() const { return header.seq; }
>> >> void set_seq(unsigned s) { header.seq = s; }
>> >> ...
>> >> }
>> >>
>> >> in src/msg/simple/Pipe.cc
>> >>
>> >> class Pipe {
>> >> ...
>> >> __u32 get_out_seq() { return out_seq; }
>> >> ...
>> >> }
>> >>
>> >> Is this bug or intentional ?
>> >
>> > That's a bug. The seq values are intended to be 32 bits.
>> >
>> > (We should also be using the ceph_cmp_seq (IIRC) helper for any inequality
>> > checks, which does a sloppy comparison so that a 31-bit signed difference
>> > is used to determine > or <. It sounds like in this case we're just
>> > failing an equality check, though.)
>> >
>>
>> struct ceph_msg_header {
>> __le64 seq; /* message seq# for this session */
>> ...
>> }
>>
>> you means we should leave the upper 32-bits unused?
>
> Oh, hmm. I'm confusing this with the cap seq (which is 32 bits).
>
> I think we can safely go either way.. the question is which path is
> easier. If we move to 32 bits used on the kernel side, will userspace
> also need to be patched to make reconnect work? That unsigned get_seq()
> is only 32-bits wide.
I don't think userspace need to be patched.
>
> If we go with 64 bits, userspace still needs to be fixed to change that
> unsigned to uint64_t.
>
> What do you think?
> sage
>
I like the 64 bits approach. Here is userspace code that checks
message sequence.
Pipe::reader() {
...
if (m->get_seq() <= in_seq) {
ldout(msgr->cct,0) << "reader got old message "
<< m->get_seq() << " <= " << in_seq << " " << m << " " << *m
<< ", discarding" << dendl;
msgr->dispatch_throttle_release(m->get_dispatch_throttle_size());
m->put();
if (connection_state->has_feature(CEPH_FEATURE_RECONNECT_SEQ) &&
msgr->cct->_conf->ms_die_on_old_message)
assert(0 == "old msgs despite reconnect_seq feature");
continue;
}
if (m->get_seq() > in_seq + 1) {
ldout(msgr->cct,0) << "reader missed message? skipped from seq "
<< in_seq << " to " << m->get_seq() << dendl;
if (msgr->cct->_conf->ms_die_on_skipped_message)
assert(0 == "skipped incoming seq");
}
m->set_connection(connection_state.get());
// note last received message.
in_seq = m->get_seq();
...
}
Looks like the code works perfectly when the two ends of connection
have different bits. We don't need to worry about the change breaks
interoperability between patched userspace and un-patched userspace.
Regards
Yan, Zheng
>
>>
>>
>> > sage
>> >
>> >
>> >> Regards
>> >> Yan, Zheng
>> >>
>> >>
>> >> > Next, we find something like this on one of the OSDs.:
>> >> > 2016-05-31 14:34:44.130279 mon.0 XX.XX.XX.188:6789/0 1272184 : cluster [INF] HEALTH_WARN; mds0: Client storage-nfs-01 failing to respond to capability release
>> >> >
>> >> > Finally, I am seeing consistent HEALTH_WARN in my status regarding trimming which I am not sure if it is related:
>> >> >
>> >> > cluster XXXXXXXX-bd8f-4091-bed3-8586fd0d6b46
>> >> > health HEALTH_WARN
>> >> > mds0: Behind on trimming (67/30)
>> >> > monmap e3: 3 mons at {storage02=X.X.X.190:6789/0,storage03=X.X.X.189:6789/0,storage04=X.X.X.188:6789/0}
>> >> > election epoch 206, quorum 0,1,2 storage04,storage03,storage02
>> >> > fsmap e74879: 1/1/1 up {0=cephfs-03=up:active}, 1 up:standby
>> >> > osdmap e65516: 36 osds: 36 up, 36 in
>> >> > pgmap v15435732: 4160 pgs, 3 pools, 37539 GB data, 9611 kobjects
>> >> > 75117 GB used, 53591 GB / 125 TB avail
>> >> > 4160 active+clean
>> >> > client io 334 MB/s rd, 319 MB/s wr, 5839 op/s rd, 4848 op/s wr
>> >> >
>> >> >
>> >> > Regards,
>> >> > James Webb
>> >> > DevOps Engineer, Engineering Tools
>> >> > Unity Technologies
>> >> > _______________________________________________
>> >> > ceph-users mailing list
>> >> > ceph-users@xxxxxxxxxxxxxx
>> >> > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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