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New Member

what happens if the service is down ??

HI

we have 3 web servers load balanced using a CSS.

The content which get to CSS is balanced among these three services.

Suppose a request came in from Customer A and css redireicts that to say service#1 and the process is going on and Customer A is is waiting for the output from service#1.

meanwhile if service#1 dies. what happens to the process??

Will the Customer A gets the output or it just hangs ??

will that process is redirected to another sercvice.

5 REPLIES
Cisco Employee

Re: what happens if the service is down ??

when the service goes down, the flows associated with this service are removed. So, next packet from client will be RESETed by the CSS so the client

should/will reopen a connection and will be loadbalanced to another server.

Gilles.

New Member

Re: what happens if the service is down ??

Is this a recent change?

There is a flow-reset-reject command under the rule to send a TCP reset if the address is unreachable - what is meant by unreachable is not defined. Is it the lack of a routing entry or an invalid ARP entry.

I had understood that the CSS will not take down sessions to services which have failed or are suspended. Letting any existing sessions complete after suspending a service is a gracefull way to take a server down.

Cisco Employee

Re: what happens if the service is down ??

I'm glad you corrected me.

I gave an answer based on something I read and apparently it was erroneous.

I went into the lab and confirmed what you mentioned.

The CSS will not touch existing flows when a service goes down or when you suspend it manually.

The flow-reset-reject command is described at

http://www.cisco.com/en/US/products/hw/contnetw/ps789/prod_release_note09186a00800ba0c6.html

I'm still trying to clarify this part.

Gilles.

Cisco Employee

Re: what happens if the service is down ??

ok - here you go for the flow-reset-reject.

It only works with layer 5 rule (url command) and it does send

a reset to active connection when the service goes down.

From internal doc and verified with lab test.

Gilles

New Member

Re: what happens if the service is down ??

Would this be applicable in the following scenario?

The content rule is a layer 5 rule (advanced-balance ssl, application ssl) and there are three services. If one of the services is suspended, and the content rule has the flow-reset-reject command configured, would all clients receive a RST?  This would terminate their flow and force a new connection to one of the services that is still active. 

Basically, looking for a means to override the graceful shutdown because it takes too long.

Thanks,

Rob

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