[jbosscache-dev] Re: Non Blocking State Transfer Status (& Integration with JGroups)

[Brian Stansberry]

Jason T. Greene wrote:
> Hi All,
> 
> I wanted to summarize my initial research into NBST. The planned design 
> (outlined in the wiki: http://www.jboss.org/community/docs/DOC-10275) 
> only needs to block transactional activity once, at the end of the 
> process when sending the tx log. Unfortunately it appears that flush and 
> partial flush can not be used for this, since the application needs the 
> ability to send state (tx log) during the flush. I.e. transactions need 
> to be paused by only 2 nodes, while the transfer state. This however is 
> not a big deal because we can just do this in JBoss Cache using a normal 
> RPC message that flips a gate.
> 
> In addition, the state transfer and streaming state transfer facilities 
> in jgroups can not be used (since they are designed around blocking the 
> entire group). This means JBoss Cache needs to stream state itself. 
> Ideally this would be a separate point-to-point connection, since we 
> don't want to pollute multicast traffic with potentially huge volumes of 
> noise. Currently jgroups does not yet support a streaming API like this:
> https://jira.jboss.org/jira/browse/JGRP-653
> 
> IMO This leaves us with 3 options:
> 
> 1. Wait on JGRP-653 (upping its priority), also add requirements for a 
> p2p connection.
> 2. Implement our own p2p connection using tcp (probably using xnio).
> 3. Somehow enhance state transfer / partial flush to meet our needs
> 
> Option 1 seems to be a useful feature for other applications. Although 
> we need feedback from Bela and Vladimir about that.
> 
> Option 2 would give us more flexibility in the implementation, however 
> care has to be taken to ensure that communication can only happen 
> between group members (for security reasons), and that the network 
> address configurations are somehow reused.
> 
> Option 3 I am less found of, since we would likely end up adding a bunch 
> of JBoss Cache specific code to JGroups that no one else would use.
> 

Option 2 makes me nervous. Two separate communication frameworks, added 
dependencies, opening new sockets etc. Sounds like integration hassles 
for sure.

-- 
Brian Stansberry
Lead, AS Clustering
JBoss, a division of Red Hat
brian.stansberry at redhat.com