[ACE] What makes a sticky reset?

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Hi,


Our websites are loadbalanced thru our ACE modules and we are using the sticky feature.

Sticky is needed so that the customers session will retain the content of its shopping basket.


About 10% of our customers complain that the basket is emptied during a session, forcing them to start over. In our logs we indeed see that some users are balanced to another server during a session. Apparently in these cases the sticky feature is ignored somehow.


My question is, what are the possible triggers that the ACE uses to dismiss the sticky for a given session and start a new one?

Could it for example be caused by an html-page containing a link to another vip than the vip the page is originally served from?

Or could a simple spelling-error in a link be the trigger?


Looking forward to any answer.


Kind regards,

Anthony van Harten

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Gilles Dufour Wed, 01/06/2010 - 08:41
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Hi,


the first common mistake is the missing 'persistence rebalance' parameter-map which tells ACE to inspect every request of a TCP connection.

This is required when users are behind a proxy which does connection sharing.


Another common mistake is the size of the sticky table.

If you have not allocated enough resources, ACE deletes the oldest entries to insert the new one.

You won't see resource deny since ACE will simply erase old entries.

So make sure you have allocated minimum 10% of sitcky resource.


Finally, the sticky timeout itself is a possibility.


Gilles.

danilodicesare Sun, 01/10/2010 - 03:38
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Hi all,


i cannot understand why you said:


'the first common mistake is the missing 'persistence rebalance' parameter-map which tells ACE to inspect every request of a TCP connection.

This is required when users are behind a proxy which does connection sharing.'


i red from user guide this:


'With persistence rebalance enabled, each subsequent HTTP request on the same TCP connection is load balanced independently.'


as i can undesrtand i have not to apply a parameter-map with persistence rebalance if i've got e-commerce stuff or i'm wrong?




Das

Gilles Dufour Mon, 01/11/2010 - 00:52
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You need persistence rebalance for users connecting through a proxy.


A proxy will open one connection with your vip and send all client requests into this single connection.

But some clients have cookie X  while other have cookie Y.

If you do not have persistent rebalance ACE will only check the first request and assume all others will go to the same server.

Again, with proxy this is not true.


Enable the command  !


Gilles.

Peter Koltl Sun, 01/10/2010 - 12:55
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Which sticky method are you using? src-IP or cookie-based? I have seen in some Oracle portal that the server sometimes switched to a new cookie value during an user session so ACE had no chance to keep the session sticky. In similar cases it's worth capturing the error and prove which component fails.

johnwilliamscisco Thu, 05/20/2010 - 02:25
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Hi, I've a similar scenario with a Cisco 4710 in a dmz, running a vip that end users are hitting from behind proxy and nat.

I enabled Cookie-Insert and its pushing down a cookie to the browser now, just wondering if I need to add persistence-rebalance when you are using cookie-insert. from the command reference it seems like all user sessions would end up on one rserver if i did that. Looking to ensure the round-robin is still used.


Usage Guidelines

With persistence rebalance enabled, when successive GET requests result  in load balancing that chooses the same policy, the ACE sends the  request to the real server used for the last GET request. This behavior  prevents the ACE from load balancing every request and recreating the  server-side connection on every GET request, producing less overhead and  better performance.

Another effect of persistence rebalance is that header insertion and  cookie insertion, if enabled, occur for every request instead of only  the first request.


thanks

John W.

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