Re: Load Balancing, no fail over when backend server is down?

Ryan Bowman <ryanlbowman@xxxxxxxxx> · Thu, 29 Mar 2012 10:14:20 -0600

That doesn't sound correct to me, the balancer-manager page has a
status column, and shows that one is OK, the other is Err. (see the
attached screen shot)

Apache knows that the backend server is having problems, shouldn't
Apache then know to send the requests to healthy nodes?

On Thu, Mar 29, 2012 at 12:34 AM, Anam Ali Khan <anamalikhan@xxxxxxxxx> wrote:
> I think Apache mod_proxy do not support health checking for backend servers.
>
> -Anam
>
> ________________________________
> From: Ryan Bowman <ryanlbowman@xxxxxxxxx>
> To: users@xxxxxxxxxxxxxxxx
> Sent: Thursday, 29 March 2012, 2:04
> Subject:  Load Balancing, no fail over when backend server is
> down?
>
> Greetings
>
> I have recently setup Apache load balancing to two backend JBoss
> (5.1.0.GA) servers. Communication over AJP, with Sticky Sessions, (no
> session replication on the Jboss servers). I'm having a problem with
> both Apache 2.2.21 (SUSE 11.3) and 2.4.1 (CentOS 5-something, I
> think).
>
> I shut off one of the jboss nodes, the balancer-manager page shows
> that node's status as Err, yet Apache is still forwarding requests to
> that server, which results in a 503.
>
> Now, I'm making some assumptions here, but they seem pretty reasonable
> to me - if one of the nodes is in error status, I assume Apache would
> not send requests to it, even with Sticky Sessions. If I leave my
> cookies as is (with the jvmRoute to the node that is down), I get a
> 503 page, which is extremely not useful, and contrary to one of the
> main reasons we put in the second JBoss server.
>
> In order to get Apache to send requests to the server that is
> available, I have to either delete/modify the browser cookie, or set
> the node status to disabled. We have monitoring in place for the
> balancer-manager page, to alert me if the status of a node changes so
> I can set it to disabled if I need to, but it seems like Apache should
> not be sending traffic, even sticky traffic, to down nodes.
>
> But what I want is that if the node is down that all requests would go
> to the up node, sticky sessions be damned. If the user's session is
> broken/reset in the server switch, that is a small thing compared to
> getting a 503 page, making them think the site is down.
>
> Can someone please tell me what am I doing wrong?
>
> <Proxy balancer://jbcluster>
>   BalancerMember ajp://jbtest1:8009 route=tn1 retry=0 loadfactor=1
>   BalancerMember ajp://jbtest2:8009 route=tn2 retry=0 loadfactor=1
>   ProxySet lbmethod=byrequests stickysession=JSESSIONID|jsessionid
> scolonpathdelim=On nofailover=Off
> </Proxy>
>
> ProxyPass /images !
> ProxyPass /apache-info !
> ProxyPass /apache-status !
> ProxyPass /balancer-manager !
>
> ProxyPassMatch
> ^(/|/cl/.*|/s/.*|/c/.*|/d/.*|/m/.*|/v/.*|/t/.*|/p/.*|/b/.*|/tw/.*)$
> balancer://jbcluster
>
> ProxyPassMatch (\.do.*|\.jsp)$ balancer://jbcluster
>
> ProxyPassMatch (.*/styles/.*\.css|/scripts/.*\.js|/pie/PIE.htc)$
> balancer://jbcluster
>
> thanks
> ryan
>
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