Issues about Couchbase cluster

hi guys,
I met a issue about couchbase cluster connection, anyone who can give me some helps?
Following are details:

I setup 3 server nodes in 1 cluster, let's named ServerNodeA, ServerNodeB, ServerNodeC.
3 nodes join as a cluster, it works well.

At the client side (with Java), my connect code is like that:

List uris = new ArrayList();

uris.add(URI.create("http://ServerNodeA:8091/pools"));
uris.add(URI.create("http://ServerNodeB:8091/pools"));
uris.add(URI.create("http://ServerNodeC:8091/pools"));

CouchbaseConnectionFactory cf = new CouchbaseConnectionFactory(uris, "default", "");
CouchbaseClient client = new CouchbaseClient(cf);

For additional, in our project, we just connect the couchbase at the first time,
we will not close the connection, this is to avoid performance issue.

now the issue comes:
After the application start(it means the connection is already setup, we can get/save data),
If ServerNodeA down, and after the auto fail-over in cluster, the CouchbaseClient still not work;
but if ServerNodeB or ServerNodeC down, after the auto fail-over, the CouchbaseClient can works.

and if i change the order in the URI list(at the java code), the condition changes.
so we can find that if the 1st server node in the list down, the CouchbaseClient doesn't work.

So how can i resolve this problem?
thanks for your help.