Hi,

I'm trying improve my TCP failover configuration on rsyslog clients.

My log architecture is:
Clients -> logrelay0{1,2}.xxxx -> Central log storage

Hereafter my clients configuration:
*.* @@logrelay01.xxx:xxx
$ActionExecOnlyWhenPreviousIsSuspended on
& @@logrelay02.xxx:xxx
$ActionExecOnlyWhenPreviousIsSuspended off

I prefer configuring failover on clients side (and not doing failover on 
centralized element between clients and logrelay).

This configuration is not enough for me, when logrelay01 (primary) is 
overloaded (but reply partially to TCP) some clients are very impacted. Some 
clients (physical and virtual) generate many logs per seconds and the failover 
from logrelay01 (primary) to logrelay02 (slave) is done too late. Logs are 
bufferized on clients up to clients become unreachable (i think CPU load 
average or RAM full).
I think this situation will occurs too if logrelay01 is off (incident or for 
maintenance), clients does not reach the logrelay01 and failover will be done 
too late.
I need to prevent these situations.

To reproduce this case, from logrelay01 i had DROP packet from one client and 
seen that client failover is done about ~2 minutes after.
I reproduce the same test with REJECT from logrelay01 too and seen that 
failover is done immediately.

I reproduced my previous problems with in DROP rule.

In this thread someone 
http://www.gossamer-threads.com/lists/rsyslog/users/14681 got close issue.

I think there is several solution to prevent my problem:
- Here 
http://blog.gerhards.net/2011/03/using-failover-and-asynchornous-actions.html 
and here http://lists.adiscon.net/pipermail/rsyslog/2015-March/040189.html you 
talk about synchronous or asynchronous queue.
- KeepAlive features has been implemented

After some configuration tests with KeepAlive, RELP, synchronous Queue, it seem 
that my version does not support those features.

Is it possible to configure fast failover (in less than 30 secondes) on client 
side with Centos 7 rsyslog version (rsyslog-7.4.7-12.el7.x86_64), what is the 
best solution for you?

As i am in degreded state in failover (primary server to secondary server) case 
i can loose some logs.

I am available if you need more informations

Thank you for you help

David
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