merlimat opened a new issue #13304:
URL: https://github.com/apache/pulsar/issues/13304


   
   
   
   ## Motivation
   
   After all the work done for PIP-45 that was already included in 2.8 and 2.9
   releases, it enabled the concept of re-acquirable resource locks and leader
   election.
   
   Another important change was to avoid doing any deferrable metadata operation
   when we know that we are not currently connected to the metadata service.
   
   Finally, that enabled to stabilize in 2.9 the configuration setting that 
allows
   brokers to continue operating in a safe mode when the session with ZooKeeper
   is expired.
   
   The way it works is that, when we lose a ZooKeeper session, the data plane 
will
   continue to work undisturbed, relying the BookKeeper fencing to avoid any
   inconsistencies.
   
   New topics are not be able to get started, but existing topics will see no
   impact.
   
   The original intention for shutting down the brokers was to ensure that we
   would automatically go back to a consistent state, with respect to which
   resources are "owned" in ZooKeeper by a given broker.
   
   With the re-acquirable resource locks, that problem was solved and thoroughly
   tested to be robust.
   
   ## Proposed changes
   
   In 2.10 release, for the setting:
   
   ```properties
   # There are two policies to apply when broker metadata session expires: 
session expired happens, "shutdown" or "reconnect".
   # With "shutdown", the broker will be restarted.
   # With "reconnect", the broker will keep serving the topics, while 
attempting to recreate a new session.
   zookeeperSessionExpiredPolicy=shutdown
   ```
   
   Change its default value to `reconnect`.
   


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