DistributedPeerManager - Cannot determine a latest common bundle, search may be blocked Error on master node

[vtalanki]

Hi,

We have disabled [distributedSearch] in out splunk cluster's master and indexer nodes. With this we are seeing below issues

WARN in Master:

WARN  DistributedPeerManager - Cannot determine a latest common bundle, search may be blocked

ERROR in Indexers:

SearchPeerBundlesSetup - Cannot find bundles for search peer: <master_ip_node>

What we tried?

1. Enabled dist search in master alone(not on indexers) - both issues are gone
2. Enabled dist search on all indexers alone(not on master) - Can still see both the issues
3. Made an update to one of the apps and did apply-bundle - This is successful without any issues

So the solution seems to be enabling dist search on master.  But wanted to get more insight into this.

1. What does dist search mean on master and indexers?
2. Does master node needs to have dist search enabled?
3. In 'Cannot determine a latest common bundle' and 'Cannot find bundles for search peer' what does bundle mean here? I'm sure these are not knowledge bundles. 
4. Why indexer is treating master as search peer?