Does Persistence Override Availability?

[Robinson, Eric]

We have 2 tomcat servers behind an lvs+ldirectord load balancer. The
pertinent section of ldirectord.cf looks like this:

# Virtual Server for tomcat(site008), Outside to Inside
virtual=192.168.5.100:3008
        real=192.168.10.61:3008 masq
        real=192.168.10.62:3008 masq
        service=http
        request="/checkup.html"
        receive="site008_tomcat_is_up"
        scheduler=lblc
        protocol=tcp
        checktype=3
        persistent=360



Normally, ipvsadm looks something like this:

[root at lb1 ]# ipvsadm|grep 3008
TCP  extrovert.mydomain.com:3008 lblc persistent 360
  -> appftp2.mydomain.com:3008     Masq    1      1          4
  -> appftp1.mydomain.com:3008     Masq    1      2          6



We turned off one of the servers and now it looks like this, which is
expected:

[root at lb1 ]# ipvsadm|grep 3008
TCP  extrovert.mydomain.com:3008 lblc persistent 360
  -> appftp2.mydomain.com:3008     Masq    0      0          3
  -> appftp1.mydomain.com:3008     Masq    1      2          6


However, users who were connected to appftp2 got "page could not be
displayed" errors, which tells me that LVS is was still directing
traffic to the down server.

After a while, the situation cleared up. I assume this is because
ipvsadm started directing traffic to the up server.

Does anyone know why this would be happening? Is my persistent=360
statement causing ipvsadm to ignore the down state of the realserver?

--
Eric Robinson
Director of Information Technology
Physician Select Management, LLC
775.720.2082


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