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From Flavio Junqueira <...@apache.org>
Subject Re: ZK read-only issue
Date Wed, 13 Jul 2016 21:06:28 GMT
From the logs, it looks like the server the client is trying to connect to is behind compared
to last zxid the client has seen:

	Refusing session request for client / as it has seen zxid 0x3 our last zxid
is 0x0 client must try another server

I believe the behavior we currently have is that a client can connect to an RO server, but
the server must have a view at least as recent as the server. 


> On 12 Jul 2016, at 16:23, Benjamin Jaton <benjamin.jaton@gmail.com> wrote:
> Hello,
> I'm having problems using ZK in read-only mode.
> I am using a fresh install of ZK 3.5.1-alpha where I configure the installation to be
in a 3 nodes ensemble.
> I start this node only (QA-E8WIN11) with -Dreadonlymode.enabled=true.
> I see that the node QA-E8WIN11 starts the RO server properly:
> 2016-07-12 16:10:10,955 [myid:1] - INFO  [Thread-4:ReadOnlyZooKeeperServer@73] - Read-only
server started
> Then I make a read-only enabled client:
>         ZooKeeper zk = new ZooKeeper("QA-E8WIN12:2181,QA-E8WIN13:2181,QA-E8WIN11:2181",
45000, this, true);
>         System.out.println("Successfully established the connection with ZooKeeper");
>         zk.getData("/", false, null);
>         System.out.println("Done.");
> Note that only QA-E8WIN11 is started, the other 2 are not.
> When the ZK client picks QA-E8WIN11 first, it works.
> But when it picks a different node, it fails with:
> 16:10:13.338 org.apache.zookeeper.ZooKeeper:716 - Initiating client connection, connectString=QA-E8WIN12:2181,QA-E8WIN13:2181,QA-E8WIN11:2181
sessionTimeout=45000 watcher=TestZkReadOnly@68de145
> Successfully established the connection with ZooKeeper
> 16:10:13.475 org.apache.zookeeper.ClientCnxn:1138 - Opening socket connection to server
QA-E8WIN13/ <>. Will not attempt to authenticate
using SASL (unknown error)
> 16:10:28.469 org.apache.zookeeper.ClientCnxn:1251 - Client session timed out, have not
heard from server in 15001ms for sessionid 0x0, closing socket connection and attempting reconnect
> 16:10:28.574 org.apache.zookeeper.ClientCnxn:1138 - Opening socket connection to server
QA-E8WIN12/ <>. Will not attempt to authenticate
using SASL (unknown error)
> Exception in thread "main" org.apache.zookeeper.KeeperException$ConnectionLossException:
KeeperErrorCode = ConnectionLoss for /
>     at org.apache.zookeeper.KeeperException.create(KeeperException.java:99)
>     at org.apache.zookeeper.KeeperException.create(KeeperException.java:51)
>     at org.apache.zookeeper.ZooKeeper.getData(ZooKeeper.java:1753)
>     at org.apache.zookeeper.ZooKeeper.getData(ZooKeeper.java:1782)
>     at TestZkReadOnly.run(TestZkReadOnly.java:26)
>     at TestZkReadOnly.main(TestZkReadOnly.java:16)
> I'm attaching all the logs. The server and the client are on the same machine QA-E8WIN11.
> Any help would be greatly appreciated!
> Thanks,
> Benjamin Jaton
> <zkclient.log><zkserver.log>

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