WADI and cluster restart

[Marcin Kwiatkowski-3]

Hello,

Does wadi detect graceful server restart (jetty in my case) and migrate
sessions from that node (not by a failover detection) to another before it
goes down?

I'm evaluating wadi usage with jetty in context of my applications. Sometimes
i need to apply hotfix while keeping application going and i'm doing it by
restarting cluster in few parts so that there are always some active nodes. I
can't lose any session data, so i need to be sure that on massive server
restart session will migrate, so if only copies of session are on those nodes,
they won't be lost.

Storing session data in database is not an option - i need memory only
replication.

Pozdrawiam,
--
Marcin Kwiatkowski

[Gianny Damour-2]

Hi Marcin,

When a node is gracefully stopped, WADI indeed migrates sessions to  
the other nodes.  No sessions are lost.

Thanks,
Gianny

On 01/11/2009, at 6:54 AM, Marcin Kwiatkowski wrote:

> Hello,
>
> Does wadi detect graceful server restart (jetty in my case) and  
> migrate
> sessions from that node (not by a failover detection) to another  
> before it
> goes down?
>
> I'm evaluating wadi usage with jetty in context of my applications.  
> Sometimes
> i need to apply hotfix while keeping application going and i'm  
> doing it by
> restarting cluster in few parts so that there are always some  
> active nodes. I
> can't lose any session data, so i need to be sure that on massive  
> server
> restart session will migrate, so if only copies of session are on  
> those nodes,
> they won't be lost.
>
> Storing session data in database is not an option - i need memory only
> replication.
>
> Pozdrawiam,
> --
> Marcin Kwiatkowski
>

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[Marcin Kwiatkowski-3]

On Saturday 31 October 2009 22:53:54 Gianny Damour wrote:

> When a node is gracefully stopped, WADI indeed migrates sessions to
> the other nodes.  No sessions are lost.

Yeap, I know that, but imagine such a scenario. Let's say I have cluster of 8
nodes, all shares the same application. And now I want to perform restart. To
speed up the restart cluster is divided into 2 groups so it restarts nodes 1,
2, 3 and 4 at once first, when they are online nodes then nodes 5, 6, 7 and 8
are restarted. Now let's say i duplicate session to 1 node. What will happen
when session is on nodes 1 and 2 during restart? I guess it'll migrate but it
might not be optimal - session may migrate to nodes 3 and 4 which are be also
restarted at about the same time. Will that work ok and sessions won't be
lost? But even if that will work - is there a way to avoid that unnecessary
migrations and inform WADI in some way that that some nodes will go offline
soon and it should migrate all sessions to other nodes?

Pozdrawiam,
--
Marcin Kwiatkowski

[Gianny Damour-2]

OK. I now see. This is not a feature provided out-of-the-box.

This is hopefully relatively easy to implement if deemed necessary.

If this is something you are really keen to have, then let me know  
and I will implement it.

Thanks,
Gianny

On 04/11/2009, at 12:59 AM, Marcin Kwiatkowski wrote:

> On Saturday 31 October 2009 22:53:54 Gianny Damour wrote:
>
>> When a node is gracefully stopped, WADI indeed migrates sessions to
>> the other nodes.  No sessions are lost.
>
> Yeap, I know that, but imagine such a scenario. Let's say I have  
> cluster of 8
> nodes, all shares the same application. And now I want to perform  
> restart. To
> speed up the restart cluster is divided into 2 groups so it  
> restarts nodes 1,
> 2, 3 and 4 at once first, when they are online nodes then nodes 5,  
> 6, 7 and 8
> are restarted. Now let's say i duplicate session to 1 node. What  
> will happen
> when session is on nodes 1 and 2 during restart? I guess it'll  
> migrate but it
> might not be optimal - session may migrate to nodes 3 and 4 which  
> are be also
> restarted at about the same time. Will that work ok and sessions  
> won't be
> lost? But even if that will work - is there a way to avoid that  
> unnecessary
> migrations and inform WADI in some way that that some nodes will go  
> offline
> soon and it should migrate all sessions to other nodes?
>
> Pozdrawiam,
> --
> Marcin Kwiatkowski
>
>

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