Hi.

**The problem**
I've configured elasticsearch for Cross Cluster Search (CCS). It works well in most cases. But I can't get a correct behaviour in a situation when a remote node becomes unavailable [by pulling a network cable off]: CCS requests start hanging up.
The expected behaviour is to get some results from available CCS nodes.

The CCS simplified deployment scheme
node1/cluster1[1 shard]/index1
node2/cluster2[1 shard]/index1

The desired behaviour
node1 can do CCS requests to index1 of node1 and node2
node2 can do CCS requests to index1 of node1 and node2

**Interesting behaviour particular qualities**
Case 1
1. node1, node2: ES are working
2. node2: pull the network cable off
3. node1: the CCS query to node2:index1 is hanging up

Case 2
1. node2: ES is working, the node is not available (by the cable) for node1
2. node1: ES is restated
3. node1: make a CCS query to node2:index1 and get a result (w/o node2 data)
4. node2: insert the network cable
5. node1: make a CCS query to node2:index1 and get a result (w/ node2 data)
6. node2: pull the network cable off
7. node1: the CCS query to node2:index1 is hanging up
 
**The used configuration**
node1.elasticsearch.yml

node1.cluster.settings

The node2 settings are similar.

**Environment**
Linux
ES 6.2.2
Java 9.X

Thank you in advance.

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