timeout - Understanding TCP dynamics -


what experiencing: have app server connects rabbitmq server. time goes on, number of established connections looking rabbitmq server goes up, count app server remains constant.

i run on both:

root@app01:~# netstat -ant | grep est | grep 5672 | grep 172.25.12.48 tcp        0      0 172.25.12.48:50587      10.48.64.230:5672       established tcp        0      0 172.25.12.48:50588      10.48.64.230:5672       established   root@rabbit01:~# netstat -ant | grep est | grep 5672 | grep 172.25.12.48 tcp6       0      0 10.48.64.230:5672       172.25.12.48:38408      established tcp6       0      0 10.48.64.230:5672       172.25.12.48:50588      established tcp6       0      0 10.48.64.230:5672       172.25.12.48:33491      established tcp6       0      0 10.48.64.230:5672       172.25.12.48:50587      established tcp6       0      0 10.48.64.230:5672       172.25.12.48:34541      established

example results give 6 on app server , 15 (even high 46) on rabbitmq server. restart rabbitmq server , normal, 2 connections each side.

i assuming either switch times out connection or application terminates process uncleanly. looking this, understand tcp behaviour better.

current settings on rabbitmq server:

tcp_retries1 set 3
tcp_retries2 set 15

so have expected see 'invalid' connections drop after around 13-30 minutes if understand forums correctly.

yet, looking @ tcp keepalive values:

tcp_keepalive_time set 7200 (so after 2h send first keepalive probe.)
tcp_keepalive_intvl 75 (so 75 seconds after first one, resend probe.)
tcp_keepalive_probes 9 (so send 9 probes in total)

so keepalive process take 7200+(9*75)=7875, or 2 hours 11 minutes before closing.

due connection (presumably) disappearing, leads 2 questions.
1. correct?
2. missing option apart switch or app terminating abnormally cause these invalid connections?

source: https://www.frozentux.net/ipsysctl-tutorial/chunkyhtml/tcpvariables.html

our f5's reason this. seems after idle timeout, f5 drops entry tables. app servers, connection invalid, , tcp closes them. rabbitmq server though, somehow connections remains valid connections. although don't understand why switch has ability keep connection state valid - but, reason.


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