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I have a direct-routed Piranha/LVS cluster that I would like
to load balance between real servers svr1 and svr2. As a test I’m
using the telnet service. For my setup, I’m using WRR, no load
monitoring right now, direct-route, weights of 1 on both svr1 and svr2, using
virtual ip address of test_vip. Also have I have ip_forward turned on on
my router machine (say it’s on host rtr1). Kernel: “2.6.9-42.0.10.ELsmp
#1 SMP Fri Feb 16 17:17:21 EST 2007”. I also have an iptables rule in the
nat table, PREROUTING chain for my telnet service and test_vip on both real
servers saying to “REDIRECT”. If I get on another machine, say client1, and telnet to
test_vip, everything works fine … meaning each subsequent connection goes
to the next server in the cluster: svr1, svr2, svr1, svr2, … However, if I run my telnet client from one of my real
servers, say svr2 connecting to my service’s virtual IP, test_vip, I will
get connected to the other real server (svr1) fine when the round-robin
schedule says I should go there, but when the schedule points me back to my
host (svr2), my connection hangs. ipvsadm -l reports that a connection
did go through the ipvs tables, but it does not connect. Same thing will happen if I start from svr1…. Works to
svr2, but hangs trying to come back to svr1, the source machine. Bottom line: it works if client is run from non-real-server
machines, and half the time if client is run from a real server machine but the
other half of the time (when redirected to itself), it hangs. (I recognize “half”
is because I just have 2 real servers.) Any clues as to why it won’t work consistently when balanced
back to itself? (Extra note: I say it works from non-real-server machines…
not completely true: doesn’t work from the router machine, rtr1, as that
always goes back to itself, rtr1, ignoring the ipvs tables apparently as
ipvsadm -l never shows the connection in its statistics… Apparently the
virtual IP address being local short-circuits the ipvs table operations). TIA. |
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