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From Matthieu Morel <mmo...@apache.org>
Subject Re: Question about dynamic application deployment
Date Thu, 03 Jan 2013 15:16:10 GMT
Hi Benjamin, some answers inline:

On Jan 3, 2013, at 15:55 , Benjamin Süß wrote:
> 
> in the overview about s4 v0.5 I there is a point mentioning "dynamic application deployment".
Unfortunately I could not find any further information about this so I have some questions:
> 
> 1.) In general, does this mean new applications can be added at cluster runtime?

We cannot have multiple S4 applications on the same logical cluster. But we can start with
"empty" nodes and dynamically deploy an application. This model facilitates porting the platform
to other infrastructures (e.g. Yarn), while keeping a common deployment scheme .

> 
> 2.) If so, how about updating existing applications

Currently we have to restart the nodes, and update the app reference in Zookeeper. (The existing
classloading machinery (inspired from Hadoop's) could probably be extended to support automatic
updating though).

> 
> 3.) If it is possible to update existing applications, what about data loss during updates?

You can recover previous state through checkpointing and recovery, but pending messages are
lost. 


Hope this helps,

Matthieu


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