Re: Ceph and TCP States

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On Mon, Oct 24, 2016 at 11:29 AM, Nick Fisk <nick@xxxxxxxxxx> wrote:
>> -----Original Message-----
>> From: Yan, Zheng [mailto:ukernel@xxxxxxxxx]
>> Sent: 24 October 2016 10:19
>> To: Gregory Farnum <gfarnum@xxxxxxxxxx>
>> Cc: Nick Fisk <nick@xxxxxxxxxx>; Zheng Yan <zyan@xxxxxxxxxx>; Ceph Users <ceph-users@xxxxxxxxxxxxxx>
>> Subject: Re:  Ceph and TCP States
>>
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>> On Sat, Oct 22, 2016 at 4:14 AM, Gregory Farnum <gfarnum@xxxxxxxxxx> wrote:
>> > On Fri, Oct 21, 2016 at 7:56 AM, Nick Fisk <nick@xxxxxxxxxx> wrote:
>> >>> -----Original Message-----
>> >>> From: ceph-users [mailto:ceph-users-bounces@xxxxxxxxxxxxxx] On
>> >>> Behalf Of Haomai Wang
>> >>> Sent: 21 October 2016 15:40
>> >>> To: Nick Fisk <nick@xxxxxxxxxx>
>> >>> Cc: ceph-users@xxxxxxxxxxxxxx
>> >>> Subject: Re:  Ceph and TCP States
>> >>>
>> >>>
>> >>>
>> >>> On Fri, Oct 21, 2016 at 10:31 PM, Nick Fisk <mailto:nick@xxxxxxxxxx> wrote:
>> >>> > -----Original Message-----
>> >>> > From: ceph-users [mailto:mailto:ceph-users-bounces@xxxxxxxxxxxxxx]
>> >>> > On Behalf Of Haomai Wang
>> >>> > Sent: 21 October 2016 15:28
>> >>> > To: Nick Fisk <mailto:nick@xxxxxxxxxx>
>> >>> > Cc: mailto:ceph-users@xxxxxxxxxxxxxx
>> >>> > Subject: Re:  Ceph and TCP States
>> >>> >
>> >>> >
>> >>> >
>> >>> > On Fri, Oct 21, 2016 at 10:19 PM, Nick Fisk <mailto:mailto:nick@xxxxxxxxxx> wrote:
>> >>> > Hi,
>> >>> >
>> >>> > I'm just testing out using a Ceph client in a DMZ behind a FW from
>> >>> > the main Ceph cluster. One thing I have noticed is that if the
>> >>> > state table on the FW is emptied maybe by restarting it or just clearing the state table...etc. Then the Ceph client will hang for a
>> long time as the TCP session can no longer pass through the FW and just gets blocked instead.
>> >>> >
>> >>> > This "FW" is linux firewall or hardware FW?
>> >>>
>> >>> PFSense running on dedicated HW. Eventually they will be in a HA pair so states should persist, but trying to work around this for
>> now.
>> >>> Bit annoying having CephFS lock hard for 15 minutes even though the network connection only went down for a few seconds.
>> >>>
>> >>>     hmm, I'm not familiar with this fw. And from my view, whether
>> >>> RST packet sent is decided by FW. But I think you can try "/proc/sys/net/ipv4/tcp_keepalive_time", if FW reset tcp session, tcp
>> keepalive should detect and send a rst.
>> >>
>> >> Yeah I think that’s where the problem lies. Most Firewalls tend to silently drop denied packets without sending RST's, so Ceph
>> effectively just thinks that its experiencing packet loss and will never retry until the 15 minute timeout period is up. Am I right in
>> thinking I can't tune down this parameter for a CephFS kernel client as it doesn't use the ceph.conf file?
>> >
>> > The kernel client has a lot of mount options and can be configured in
>> > a few ways via debugfs et al; I think there's a setting for the
>> > timeout as well. If you can't find it, I'm sure Zheng knows. :) -Greg
>>
>> So far, there is no mount option to control keepalive time for client-to-mds connection.
>
> I think, although can't be 100%, that most of the problem is around client<->mon traffic. I'm pretty sure I saw a timeout to one of the mons flash up on the screen just before everything sprung back into life.

Which kernel is this?  kernel client <-> mon session has a 30 second
keepalive timeout in recent kernels.

Thanks,

                Ilya
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