[jboss-dev-forums] [JBoss AS Development] - Graceful Shutdown

[ALRubinger]

@see https://jira.jboss.org/jira/browse/JBBOOT-116

The objective discussed at the AS Design Meeting was to allow for all current requests and sessions to continue operating as expected while disallowing new ones.  Only after a subsystem has completed all of its pending work may it be brought out of service.

Initially we'd tossed around the idea of a registration API alongside jboss-bootstrap which would allow components to opt-in to receive a 2-phase event, and handle accordingly.  But this doesn't handle dependencies between subsystems:

Web request > Servlet > SLSB > JCA > MDB

This means that web must stop accepting requests before EJB3 does, else the request will break during the invocation.  For this Brian, Jesper and I have discussed leveraging the MC  dependency chain to do this a bit more intelligently.

The solution on the table is to add a "pre-stop" phase.  Subsystems may handle @PreStop lifecycle events, and MC will guarantee that these are fired in order (assuming the dependencies are explicitly and correctly declared between components).

So for instance: 

@PreStop
  | public void gracefulShutdownPrepare(){
  | // Shut down listener for new requests
  | listener.stop();
  | 
  | // Block until all current sessions have ended or are expired
  | while(hasCurrentSessions()){
  | Thread.sleep(1000);
  | }
  | 
  | // OK, go on to the next dep in the chain
  | return;
  | }

S,
ALR

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