[jboss-user] [JBossCache] - Re: Buddy replication behavior

[manik.surtani@jboss.com]

Correct, this is what is expected.

You need to 

1) enable gravitation explicitly if you want to pull data out of a potential backup scenario (this is necessary as a separate option to prevent calls trying to gravitate data for data that does not exist.  E.g., If I try 


  | String[] s = {"/one", "/two", "/three", "/four", "/five",
  |                     "/six", "/seven", "/eight", "/nine", "/ten"};
  | 
  | for (String fqn : s) cache[1].get(fqn);
  | 

I don't want expensive network calls (esp. if the cluster is big) to go out when looking for nodes four to ten.  

This is why when you know about a view-change event (perhaps by using a listener) you can execute gravitate calls.

2)  Gravitation should not happen automatically - only when a gravitation call occurs, and even then, only for the node being called.  This is to prevent a "network storm" when a node dies.  Let's assume each node has 1GB of data.  If a node dies, I don't want 1GB of network traffic of data being gravitated, since this may then kill other nodes or cause the network to be unresponsive.  

This is why this happens lazily, when a node is requested.

Hope this helps,
Manik

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