Added a wait-for-activation option to shared-store master HA policies.
This option is enabled by default to ensure unchanged server startup behavior.
If this option is enabled, ActiveMQServer.start() with a shared-store master server will not return
before the server has been activated.
If this options is disabled, start() will return after a background activation thread has been started.
The caller can use waitForActivation() to wait until server is activated, or just check the current activation status.
The failback process needs to be deterministic rather than relying on various
incarnations of Thread.sleep() at crucial points. Important aspects of this
change include:
1) Make the initial replication synchronization process block at the very
last step and wait for a response from the replica to ensure the replica has
as the necessary data. This is a critical piece of knowledge during the
failback process because it allows the soon-to-become-backup server to know
for sure when it can shut itself down and allow the soon-to-become-live
server to take over. Also, introduce a new configuration element called
"initial-replication-sync-timeout" to conrol how long this blocking will occur.
2) Set the state of the server as 'LIVE' only after the server is fully
started. This is necessary because once the soon-to-be-backup server shuts
down it needs to know that the soon-to-be-live server has started fully before
it restarts itself as the new backup. If the soon-to-be-backup server restarts
before the soon-to-be-live is fully started then it won't actually become a
backup server but instead will become a live server which will break the
failback process.
3) Wait to receive the announcement of a backup server before failing-back.
Bernd Gutjahr
Andy Taylor
Pat Fox
jbertram
Ville Skyttä
Martyn Taylor
Andy Taylor
Justin Bertram