I think this is so that the thread that calls shutdown() is guaranteed to see the latest value of acceptor. The thread that calls shutdown() is typically different from the thread that calls startup() where acceptor is initialized.
Thanks, Jun On Tue, Mar 31, 2015 at 4:54 PM, Gwen Shapira <gshap...@cloudera.com> wrote: > Hi, > > In SocketServer.scala, acceptor is defined as a volatile var: > > https://github.com/apache/kafka/blob/trunk/core/src/main/scala/kafka/network/SocketServer.scala#L54 > > My understanding is that @volatile is used to protect variables that > are accessed and modified by multiple threads. However, it looks like > acceptor variable is only accessed by the main KafkaServer thread. > > Am I missing anything? What are we protecting the acceptor from? > > The reason I'm asking is that when modifying the code for multi-port > access, I turned a single acceptor var into a ConcurrentHashMap. > However, if there are no threads accessing this variable, it probably > doesn't need to be a ConcurrentHashMap, and it probably doesn't need > to be a volatile either. > > Debugging concurrency issues after the fact is tricky, so it will be > nice if someone who worked on this can comment :) > > Gwen >
