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From graham sanderson <>
Subject Re: binary protocol server side sockets
Date Wed, 09 Apr 2014 20:17:22 GMT
Thanks Michael,

Yup keepalive is not the default. It is possible they are going away after nf_conntrack_tcp_timeout_established;
will have to do more digging (it is hard to tell how old a connection is - there are no visible
timers (thru netstat) on an ESTABLISHED connection))…

This is actually low on my priority list, I was just spending a bit of time trying to track
down the source of 

ERROR [Native-Transport-Requests:3833603] 2014-04-09 17:46:48,833 (line
222) Unexpected exception during request Connection reset by peer
	at Method)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(
	at java.util.concurrent.ThreadPoolExecutor$

errors, which are spamming our server logs quite a lot (I originally thought this might be
caused by KEEPALIVE, which is when I realized that the connections weren’t in keep alive
and were building up) - it would be nice if netty would tell us which a little about the Socket
channel in the error message (maybe there is a way to do this by changing log levels, but
as I say I haven’t had time to go digging there)

I will probably file a JIRA issue to add the setting (since I can’t see any particular harm
to setting keepalive)

On Apr 9, 2014, at 1:34 PM, Michael Shuler <> wrote:

> On 04/09/2014 12:41 PM, graham sanderson wrote:
>> Michael, it is not that the connections are being dropped, it is that
>> the connections are not being dropped.
> Thanks for the clarification.
>> These server side sockets are ESTABLISHED, even though the client
>> connection on the other side of the network device is long gone. This
>> may well be an issue with the network device (it is valiantly trying
>> to keep the connection alive it seems).
> Have you tested if they *ever* time out on their own, or do they just keep sticking around
forever? (maybe 432000 sec (120 hours), which is the default for nf_conntrack_tcp_timeout_established?)
Trying out all the usage scenarios is really the way to track it down - directly on switch,
behind/in front of firewall, on/off the VPN.
>> That said KEEPALIVE on the server side would not be a bad idea. At
>> least then the OS on the server would eventually (probably after 2
>> hours of inactivity) attempt to ping the client. At that point
>> hopefully something interesting would happen perhaps causing an error
>> and destroying the server side socket (note KEEPALIVE is also good
>> for preventing idle connections from being dropped by other network
>> devices along the way)
> Tuning net.ipv4.tcp_keepalive_* could be helpful, if you know they timeout after 2 hours,
which is the default.
>> rpc_keepalive on the server sets keep alive on the server side
>> sockets for thrift, and is true by default
>> There doesn’t seem to be a setting for the native protocol
>> Note this isn’t a huge issue for us, they can be cleaned up by a
>> rolling restart, and this particular case is not production, but
>> related to development/testing against alpha by people working
>> remotely over VPN - and it may well be the VPNs fault in this case…
>> that said and maybe this is a dev list question, it seems like the
>> option to set keepalive should exist.
> Yeah, but I agree you shouldn't have to restart to clean up connections - that's why
I think it is lower in the network stack, and that a bit of troubleshooting and tuning might
be helpful. That setting sounds like a good Jira request - keepalive may be the default, I'm
not sure. :)
> -- 
> Michael
>> On Apr 9, 2014, at 12:25 PM, Michael Shuler <>
>> wrote:
>>> On 04/09/2014 11:39 AM, graham sanderson wrote:
>>>> Thanks, but I would think that just sets keep alive from the
>>>> client end; I’m talking about the server end… this is one of
>>>> those issues where there is something (e.g. switch, firewall, VPN
>>>> in between the client and the server) and we get left with
>>>> orphaned established connections to the server when the client is
>>>> gone.
>>> There would be no server setting for any service, not just c*, that
>>> would correct mis-configured connection-assassinating network gear
>>> between the client and server. Fix the gear to allow persistent
>>> connections.
>>> Digging through the various timeouts in c*.yaml didn't lead me to a
>>> simple answer for something tunable, but I think this may be more
>>> basic networking related. I believe it's up to the client to keep
>>> the connection open as Duy indicated. I don't think c* will
>>> arbitrarily sever connections - something that disconnects the
>>> client may happen. In that case, the TCP connection on the server
>>> should drop to TIME_WAIT. Is this what you are seeing in `netstat
>>> -a` on the server - a bunch of TIME_WAIT connections hanging
>>> around? Those should eventually be recycled, but that's tunable in
>>> the network stack, if they are being generated at a high rate.
>>> -- Michael

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