A process cannot connect to port 9102 opened by the indexer. Those are the ports that, by default, should be opened by the indexer:
netstat -lnp | grep indexer tcp6 0 0 :::9100 :::* LISTEN 30575/indexer tcp6 0 0 :::9101 :::* LISTEN 30575/indexer tcp6 0 0 :::9102 :::* LISTEN 30575/indexer
In my case it was because the indexer could not talk to the projector that was not started because port 9999 was already in use (so projector could not start and indexer was trying to talk to that other service using port 9999):
netstat -lnp | grep 9999 tcp6 0 0 :::9999 :::* LISTEN 30566/projector
In /opt/couchbase/var/lib/couchbase/logs/projector.log I could actually notice:
[Error] pram[:9999] listen failed listen tcp :9999: bind: address already in use
Note: in my case, the problem was with a simple node and the N1QL query to create a primary index timing out. Not sure that solving your indexer issue will solve your problem, but it will at least make logs easier to read