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From Sten Spans <s...@blinkenlights.nl>
Subject Re: HA redundant virtual router
Date Tue, 17 Sep 2013 07:07:30 GMT
On Mon, 16 Sep 2013, Sheng Yang wrote:

> The reason for no HA as I said before, due to the complexity. E.g, if there
> can be 3 routers in the network(which control network is down but not the
> guest network), and it would cause two of them with the same priority(at
> certain time). The doc is mainly for describing the current policy and
> reason, as the basic for possible improvement.
>
> I haven't thought much about redundant router with HA, but many times we're
> dealing with intermittent network issue, so you try to plug off then plug
> in the network cable to see if HA works as expect.
>
> The priority cannot changed on the fly, it's a parameter of keepalived
> process, which is running. So at least both router need to be stopped
> before priority reset. And it's not reset to minimum, since the value can
> go up or down based on the different cases.

Looking at the doc you wrote I see no mention of HAProxy.
Is this intentional?

A failure of HAProxy (which we've observed in practice) would
result in a loss of service for loadbalanced ports.

Currently I'm thinking of adding something like the following:

  diff -Nru keepalived.conf.templ.orig keepalived.conf.templ
--- keepalived.conf.templ.orig  2013-09-17 09:02:28.410646521 +0200
+++ keepalived.conf.templ       2013-09-17 09:03:34.131434084 +0200
@@ -19,6 +19,12 @@
     router_id [ROUTER_ID]
  }

+vrrp_script check_haproxy {
+    script "/usr/bin/killall -0 haproxy"
+    interval 5
+    weight 10
+}
+
  vrrp_script check_bumpup {
      script "[RROUTER_BIN_PATH]/check_bumpup.sh"
      interval 5
@@ -47,6 +53,7 @@
      }

      track_script {
+        check_haproxy
          check_bumpup
          heartbeat
      }


This would boost vrrp priorities if haproxy is running, trigger
a failover if it fails, and should be harmless on hosts not running 
haproxy.

-- 
Sten Spans

"There is a crack in everything, that's how the light gets in."
Leonard Cohen - Anthem

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