[infinispan-dev] Non-tx X-Site: doubts and opinions

[Pedro Ruivo]

Hi guys,

I'm digging in detail in X-Site code and I have a couple of 
doubts/comments.

*Note*: I'm talking about non-tx caches :)

First, I've noticed that we are forcing the /site_master/ node to have a 
reference to the cache in order to perform the modifications from other 
sites. IMO, it can be possible the user may not want to have that cache 
running that node. WDYT?

My idea is, if the /site_master/ has the reference to the cache, it can 
use, otherwise it multicast the command to all the nodes in the site. 
The nodes that does not have the cache (or if they are not primary owner 
of any key) will ignore the command :)

Second and finally, I find a couple of optimization that can be done. #1 
I've noticed that we are sending the conditional commands to the backup 
sites without checking if the command is successful in the originator 
site. I think we can save network bandwidth and time to avoid 
serializing the commands that will fail...

#2 Also, the originator is the node that sends the command to the other 
sites. IMO, it can generate inconsistencies because 2 or more nodes in 
/site_a/ can update the same key concurrently and other /site_b/ can 
receive the commands in different order (at least, I didn't see any 
protection mechanism against this case)
I think the backup to other sites should be sent by the /primary_owner/ 
(lock owner).

Thanks in advance for the feedback.

Cheers and Happy New Year :)
Pedro