remember that CLUSTERIP is a load balancing mechinism, it doesn't do
failover.
you can configure a VIP on one of the boxes by just defining a static
address on eth0:0
where you need a HA application is to detect that one of the boxes has
died and therefor the other box should take over the VIP
With CLUSTERIP, if you configure both systems with the same IP as box 1/1,
then both will get the traffic if it's UDP (if it's TCP you will have the
same effect as a dup IP, and will probably have nothing get through). This
can be a _very_ useful feature as it allows the log message to be sent
once and received by multiple boxes, but I don't think it's what you were
after.
David Lang
On Thu, 19 Apr 2012, Martinez, Carlos R wrote:
Thanks David... it is looking like to reliably do this I'm going to have
to leverage an HA application with static VIP but I still wonder if I
can get away with iptables CLUSTERIP option.
We have our own HA application tool that we use and will need to pursue using
it...
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of [email protected]
Sent: Thursday, April 19, 2012 12:18 PM
To: rsyslog-users
Subject: Re: [rsyslog] rsyslog | VIP
You can use heartbeat (http://linux-ha.org) running on your rsyslog servers to
manage a VIP on the servers themselves (no need for an external load balancer
device)
The hard part of the question comes when you need to determine under what
conditions you want to declare a box dead to force a failover.
From a practical point of view, rsyslog is pretty darn reliable, so if you just
run rsyslog on both systems and only configure heartbeat to failover if a box
is completely dead you will be in pretty good shape.
Hoever, this would not work in the case where rsyslog stops on a box that is
otherwise healthy. How much checking you want to do to decide if rsyslog is
healthy can be complex, various tests can include:
1. is rsyslog running (simple ps |grep check)
2. is rsyslog listening to a port (lsof check, netstat check, or probing a
port)
3. is rsyslog processing the message (sec watching for a message from rsyslog
on a file or named pipe)
4. internal status checking in rsyslog
There are also other subtle prroblems that a box can have that will make a box
still think it's healthy, but not be working properly for your logging
For example:
Routing problems could cause a box to still be up, but be unable to talk to
boxes on other networks
Disk I/O problems could cause the box to be unable to write logs, even though
it can still receive them (or if the box is a relay, a downstream box could be
not responding so it can't forward the log messages)
If a box runs out of memory, various things on the box will get killed, which
may leave a box not working the way it should
I have had about a hundred pairs of boxes running heartbeat for the last decade
(more at some points than at others, but averaging around a hundred
pairs) and I've only had about a dozen or so problems stranger than what the
simplist heartbeat configuration detects (full box down issues) during that
time, which is why I say that as a practical matter, you are probably just fine
with the simplest configuration, without trying to monitor rsyslog explicitly.
David Lang
On Thu, 19 Apr 2012, Martinez, Carlos R wrote:
Date: Thu, 19 Apr 2012 13:47:39 +0000
From: "Martinez, Carlos R" <[email protected]>
Reply-To: rsyslog-users <[email protected]>
To: "[email protected]" <[email protected]>
Subject: [rsyslog] rsyslog | VIP
I'm looking for the best way to put my rsyslog servers behind a VIP for TCP &
UDP traffic.
It appears that the best solution thus far at least for TCP is fault tolerant
setup with port probing. I have tried a VIP load balance/round-robin
configuration but it takes a while for the syslog/rsyslog client to start
logging to the surviving rsyslog server when I bring one down. As for UDP I'm
not having good results at all and I'm starting to wonder if the best solution
would be to have a static VIP IP where I use CLUSTERIP configuration on my
systems where the failover occurs over the virtual network interface.
Any suggestions is appreciated.
Here is my configuration:
syslog/rsyslog client ->->->-> VIP ->->->-> rsyslog_server1,
rsyslog_server2
VIP options: 1) fault tolerant w/port probing 2) load balance/round robin 3)
static IP (multicast) utilizing CLUSTERIP option.
I prefer the load balance configuration for data center HA.
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