[ZOOKEEPER-1495] ZK client hangs when using a function not available on the server.

• Type: Bug
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 3.4.2, 3.3.5
• Fix Version/s: 3.4.6, 3.5.0
• Component/s: server

Environment

all

• Hadoop Flags: Reviewed
• Assignee: Nicolas Liochon
• Reporter: Nicolas Liochon
• Created: 28/Jun/12 07:51
• Updated: 13/Mar/14 18:16
• Resolved: 25/Jan/13 01:37

Description

This happens for example when using zk#multi with a 3.4 client but a 3.3 server.

The issue seems to be on the server side: the servers drops the packets with an unknown OpCode in ZooKeeperServer#submitRequest

public void submitRequest(Request si) {
    // snip
    try {
        touch(si.cnxn);
        boolean validpacket = Request.isValid(si.type); // ===> Check on case OpCode.*
        if (validpacket) {
            // snip
        } else {
            LOG.warn("Dropping packet at server of type " + si.type);
            // if invalid packet drop the packet.
        }
    } catch (MissingSessionException e) {
        if (LOG.isDebugEnabled()) {
            LOG.debug("Dropping request: " + e.getMessage());
        }
    }
}

The solution discussed in ZOOKEEPER-1381 would be to get an exception on the client side then & close the session.

Issue Links

• is related to: HBASE-5843 Improve HBase MTTR - Mean Time To Recover
• relates to: ZOOKEEPER-1381 Add a method to get the zookeeper server version from the client