Servers randomly stop processing requests

[ian.a.lawrence]

Hi,

We have a Cisco ACE and 8 web servers in a server farm. The load balancing predictor is set for least connections. Randomly any one of the 8 servers will stop prcessing the requests and they queue up inbound to the server. The way to clear the queue is to take that server out of service with "no inservice" and at that point the queue starts to clear down. The server can then be put back inservice and works fine. Is there anything on the ACE that could cause this behaviour.

Many thanks.

[ajayku2]

Hi,

It looks more like server issue. Check if in that situation server is hitting its limit. You can also define on ACE how many connection ACE should send to server.

Ideally when you do no inservice. No new connection goes to rserver and the number of connection starts going down making space for new connection or the connection in the queue.

regards,

Ajay Kumar

[Jorge Bejarano]

Ian,

It might be possible your servers are getting more connections than they can handle.

You may test with another predictor method just to see how it behaves with a different distribution of connections, additionally you may specify the amount of connections which a specific server can handle.

Jorge

[ian.a.lawrence]

Many thanks for the feedback.

Jorge, when you say "you may specify the amount of connections which a specific server can handle", is this configurable on the ACE device?

Regards,

Ian.

[ajayku2]

Hi Ian,

Here it is

To prevent the real server from becoming overloaded, configure connection limits.

host1/Admin(config-rserver-host)# conn-limit max 20000000 min 
15000000

As per the documentation:

Configuring Real Server Connection Limits

To prevent a real server from being overburdened, you can limit the   maximum number of active connections to the server. You can set the   maximum and minimum connection thresholds by using the conn-limit command in either real server host or real server redirect configuration mode. The syntax of this command is as follows:

conn-limit max maxconns min minconns

regards,

Ajay Kumar

[ian.a.lawrence]

Ajay,

I will try this. Very helpful of you.

Much appreciate.

Ian.

[Jorge Bejarano]

Ian,

Ajay already posted what I was talking about.

Jorge