NGINX Reverse Proxy terminate TCP connection after 5 minutes of inactivity

[J Carter]

Hello,

On Tue, 20 Feb 2024 09:40:13 +0800
Kin Seng <ckinseng at gmail.com> wrote:

> Hi J Carter,
> 
> This is the only results from the whole 5 minutes session (intentionally
> without any transaction to create inactivity). Is there any symptoms which
> can prove that other parties are the one who Initiate the closing?
> 

Packet capture is the easiest, however it looks like you have
missing data in PCAP for some reason (like tcpdump filters).

I suppose you could also perform packet capture on the client app host
instead of on the nginx host to corroborate the data - that would show
who sent FIN first.

Also, as Roman says in adjacent thread, debug level logs will also show
what happened.

> On Tue, Feb 20, 2024, 9:33 AM J Carter <jordanc.carter at outlook.com> wrote:
> 
> > Hello,
> >
> > On Mon, 19 Feb 2024 16:24:48 +0800
> > Kin Seng <ckinseng at gmail.com> wrote:
> >
> > [...]  
> > > Please refer to the attachments for reference.
> > >
> > > On Mon, Feb 19, 2024 at 4:24 PM Kin Seng <ckinseng at gmail.com> wrote:  
> > > > After capturing the tcp packet and check via wireshark, I found out  
> > that  
> > > > the nginx is sending out the RST to the public server and then send  
> > FIN/ACK  
> > > > (refer attached pcap picture) to client application.
> > > >
> > > > I have tried to enable keepalive related parameters as per the nginx
> > > > config above and also check on the OS's TCP tunable and i could not  
> > find  
> > > > any related settings which make NGINX to kill the TCP connection.
> > > >
> > > > Anyone encountering the same issues?
> > > >  
> >
> > The screenshot shows only 1 segment with FIN flag set too which is
> > odd - there should be one from each party in close sequence. Also the
> > client only returns an ACK, rather than FIN+ACK, which it should if
> > nginx was the initiator of closing the connection...
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