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From Christopher Schultz <ch...@christopherschultz.net>
Subject Re: Is it possible to expire jvmRoute cookie
Date Thu, 06 Dec 2012 23:07:39 GMT
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Konstanti,

On 12/6/12 3:39 PM, Konstantin Kolinko wrote:
> 2012/12/6 Smith, Mitchell <mitchell.smith@cwc.com>:
>> 
>> I have a jvmRoute appended to my JSESSIONID to enable sticky
>> sessions at an application level.
>> 
>> I see often that users do not close browsers, resulting (even if
>> the tomcat session has expired) the user to be forwarded back to
>> the instance.
>> 
>> Is it possible to set an expiry for the jvmRoute / JSESSIONID to
>> be expired at the browser so after x amount of time since last
>> request the jvmRoute is not transmitted back to the application
>> apache load balancer. This would prevent users constantly being
>> directed to the same application node.
>> 
> 
> 1. Even if one can set expiration time for the session cookie 
> (configurable in a Servlet 3.0 compliant application), you cannot
> do anything if somebody publishes a link containing a jsessionid in
> it somewhere, e.g. on a forum.
> 
> What I can think of is to make the jvmroute itself temporary e.g.
> by changing it periodically.
> 
> 2. How one additional user can be a problem in such a system? If
> he accesses a heavy-loaded system the things will be slow for him,
> but faster for all others, who close their browsers regularly.

Let's take a pathological example:

Assumptions:
1. Cluster has 3 nodes (A, B, C)
2. Users never close their browsers

Let's say that server A is rock-solid and never goes down. Servers B
and C are running Gentoo Linux or Debian Sid or Microsoft Windows or
have flaky hardware and so they crash or need to be rebooted all the
time; perhaps daily.

Users on nodes B and C will constantly fail-over to node A.

Those users will stick on node A pretty much forever.

Therefore node A always gets most of the traffic, and nodes B and C
only get "new" users for a while before failing-over. Even if nodes B
and C can handle 1/3 of the load, they will get much less than that,
and node A will, over time, accumulate users without bound.

It would be nice to avoid this kind of situation.

> So one could recommend that if things go slow to close one's
> browser, clean caches, or even reboot. ;)

If I called tech support for a website and they told me I needed to
close my browser or reboot my computer to just to use their website, I
would assume that they were complete idiots. If I want to be lied to
about what the problem is, I'll call my home broadband provider.

- -chris
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