on resync client should generate session expired exception if there is no
server in cluster with acceptable zxid
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Key: ZOOKEEPER-583
URL: https://issues.apache.org/jira/browse/ZOOKEEPER-583
Project: Zookeeper
Issue Type: Bug
Components: c client, java client
Affects Versions: 3.2.1, 3.1.1
Reporter: Patrick Hunt
Fix For: 3.3.0
Both the c and java clients attempt to connect to a server in the cluster by
iterating through
a randomized list of servers as listed in the connect string passed to the
zookeeper_init (c)
or ZooKeeper constructor (java). The clients do this indefinitely, until
successfully connecting
to a server or until the client is close()ed. Additionally if a client is
disconnected from a server
it will attempt to reconnect to another server in the cluster, in this case it
will only connect
to a server that has the same, or higher, zxid as seen by the client on the
previous server that
it was connected to (this ensures that the client never sees old data).
In some weird cases (in particular where operators reset the server database,
clearing out the
existing snapshots and txnlogs) existing clients will now see a much lower zxid
(due to the
epoch number being reset) regardless of the server that the client attempts to
connect to. In this
case the current client will iterate essentially forever.
Instead the client should throw session expired in this case (notify any
watchers). After iterating
through all of the servers in the list, if none of the servers have an
acceptable zxid the client
should expire the session and shut down the handle. This will ensure that the
client will eventually
shutdown in this unusual, but possible (esp with server operators who don't
also control the
clients) situation.
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