Outputs.conf need to point to each indexer in your instance, not the cluster master. The cluster master doesn't designate to members where to index, but where to search.
OK, thanks. I will make the configuration of outputs.conf accordingly. It does seem that this mechanism adds to the management complexity of forwarding the internal search head member data to the index cluster (which is indicated as a best practice), especially if the members of an index cluster are going to grow as the index cluster needs to grow for capacity/performance reasons.
On the other hand, using shc deployers to push the configuration changes to the shc members reduces some of this administrative burden, I suppose.
It's kind of too bad that the outputs.conf can't just point to the index cluster master node and let some internal mechanisms between the index cluster master and the shc members take care of the forwarding interactions, but if that's not how it works that's just the way it is - lol.
Outputs.conf need to point to each indexer in your instance, not the cluster master. The cluster master doesn't designate to members where to index, but where to search.