My app includes the definition of a summary index in indexes.conf. When I am providing a copy of the app for clustered/distributed Splunk Enterprise environments, I like to split the app into two versions: one for the search heads and one for the indexers.
Regarding the summary index definition in indexes.conf, should I include the definition in the search head version of the app or the indexer version of the app? Does it matter either way? Should I only include it in the indexer version if the environment is configured to index the summary data on the indexers (i.e., the outputs.conf is configured to forward summary data to the indexers)?
Am I understanding you correctly in that defining the sumary index (or any index for that matter) in indexes.conf and loading that file on both search heads and indexers will not cause problems?
Having the indexes.conf definition on both the search heads and the indexers won't cause problems - both will create an empty index, but only the indexers will write data to it assuming your search heads forward their data.
For example, your search heads all have a main index, or _internal, or _audit, or _introspection... yet the data for those is only stored on the indexers.
The indexes.conf should be in Indexers (must). If your summary index searches are already available in the app (already created to use the summary indexes), then the indexes.conf is not required on Search Head. However if you want the summary index to be available for use (for other searches that want to use the same summary index), then you should keep a copy of Indexes.conf on Search Head as well (then only they'll appear on summary index dropdown on create search page).