Re: Streaming replication connection break - unexpected EOF on standby connection

Hi,

After analysis by network team, they found packets are getting reset by
Secondary server. Below are the logs.

782.822280 port7 in <Secondary_server_IP>.35918 ->
<Primary_server_IP>.5433: rst 1232664740

782.822310 wan2 out <Secondary_server_IP>.35918 ->
<Primary_server_IP>.5433: rst 1232664740

782.822313 port7 in <Secondary_server_IP>.35918 ->
<Primary_server_IP>.5433: rst 1232664740

782.822315 wan2 out <Secondary_server_IP>.35918 ->
<Primary_server_IP>.5433: rst 1232664740

782.822317 port7 in <Secondary_server_IP>.35918 ->
<Primary_server_IP>.5433: rst 1232664740

782.822319 wan2 out <Secondary_server_IP>.35918 ->
<Primary_server_IP>.5433: rst 1232664740

782.822345 port7 in <Secondary_server_IP>.35918 ->
<Primary_server_IP>.5433: rst 1232664740

But they didn't able to find why secondary generating reset packet. There
are no any devices between these servers which can modify the packets.
Though both servers are on different firewall, but packets are getting
reset at secondary server and not at the firewall level, we can see this in
the log.

Below points I would like to mention about application
1. This connection interruption happens in day time, when transactions are
little bit high. In day time, average transactions per second are 5
(Inserts and processing).
2. We are not using connection pool, so each time request comes app server
creates new connection to db server and when processing is done, app server
disconnects.

We are now clue less why secondary server resetting the packets. Any help
is highly appreciated.

Thanks & Regards,
Ganesh.

On Thu, Jun 28, 2018 at 3:38 PM Ganesh Korde <ganeshakorde(at)gmail(dot)com> wrote:

> Hi Johannes,
>
> Thanks for your reply. We are using VPN Tunnel between these two hosts.
> I will check with network team, with remaining questions you mentioned and
> will get back.
>
> Thanks & Regards,
> Ganesh.
>
> On Wed, Jun 27, 2018 at 6:46 PM Johannes Truschnigg <
> johannes(at)truschnigg(dot)info> wrote:
>
>> Hi Ganesh,
>>
>>
>> On Wed, Jun 27, 2018 at 06:37:25PM +0530, Ganesh Korde wrote:
>> > [...]
>> > 1. Because of what reason, " unexpected EOF on standby connection"
>> occurs
>> > on primary db server?
>> > 2. After replication disconnection, secondary should immediately
>> connect to
>> > primary, but it takes some time, what could be the reason for this?
>>
>> From skimming the log, it seems to me that there is an issue at the
>> socket/network level, which yields the "connection reset by peer" eror
>> message.
>>
>> What is the network between these two hosts like? Is it a WAN link; is a
>> VPN
>> or SSH tunnel involved? Do you have other, long-running TCP sessions
>> between
>> these peers, and do they experience similar or other problems? Do the
>> hosts'
>> link-layer stats hint at problems, e. g. packet loss? Do the hosts'
>> kernels
>> leave a message hinting at L2 connectivity problems in their debug
>> ringbuffers
>> (`dmesg`) at the time you observe the replication drop out?
>>
>> --
>> with best regards:
>> - Johannes Truschnigg ( johannes(at)truschnigg(dot)info )
>>
>> www: https://johannes.truschnigg.info/
>> phone: +43 650 2 133337
>> xmpp: johannes(at)truschnigg(dot)info
>>
>> Please do not bother me with HTML-email or attachments. Thank you.
>>
>