Re: [infinispan-dev] Blocking issue in TO State Transfer

Adding inifinispan-dev, as other people might be interested in this as well. On 26 Feb 2013, at 10:57, Pedro Ruivo wrote: > hi, > > I found the blocking problem with the state transfer this morning. It > happens because of the reordering of a regular and OOB message. > > Below, is a simplification of what is happening for two nodes > > A: total order broadcasts rebalance_start > > B: (incoming thread) delivers rebalance_start > B: has no segments to request so the rebalance is done > B: sends async request with rebalance_confirm (unicast #x) > B: sends the rebalance_start response (unicast #x+1) (the response is > a regular message) > > A: receives rebalance_start response (unicast #x+1) > A: in UNICAST2, it detects the message is out-of-order and blocks the > response in the sender window (i.e. the message #x is missing) > A: receives the rebalance_confirm (unicast #x) > A: delivers rebalance_confirm. Infinispan blocks this command until > all the rebalance_start responses are received ==> this originates a > deadlock! (because the response is blocked in unicast layer) wondering why does this happen: the "rebalance_start response" (regular unicast #x+1) should not wait for the rebalance_confirm (OOB message) as there's no ordering between them, but be passed up the stack by jgroups.