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Hat-tip to https://github.com/sbridges for pointing this out
It turns out there is an edge case that exists when creating sequential-ephemeral nodes. The creation can succeed on the server, but the server can crash before the created node name is returned to the client. However, the ZK session is still valid so the ephemeral node is not deleted. Thus, there is no way for the client to determine what node was created for them.
Putting the create builder into protected-ephemeral-sequential mode works around this. The name of the node that is created is prefixed with a GUID. If node creation fails the normal retry mechanism will occur. On the retry, the parent path is first searched for a node that has the GUID in it. If that node is found, it is assumed to be the lost node that was successfully created on the first try and is returned to the caller.