Migrate Milliner from crayfish+alpaca

[joecorall]

Summary

The original crayfish microservices crayfits, homarus, houdini, hypercube have scyllaridae equivalents defined in isle-buildkit.

The Milliner Crayfish microservice (which indexes drupal entities into Fedora) needs an alternative implementation in order to deprecate:

• https://github.com/Islandora/Crayfish
• https://github.com/Islandora/Crayfish-Commons
• https://github.com/Islandora/islandora-fedora-entity-mapper

The fcrepo indexing logic is currently split between alpaca, crayfish-commons, islandora-fedora-entity-mapper, and Milliner. The logic should consolidate into a single implementation to allow deprecating Crayfish, Crayfish-Commons, and islandora-fedora-entity-mapper

[kayakr]

@joecorall It would be good to simplify the architecture where possible. However, have you considered replacing fcrepo-indexer and blazegraph-indexer with a Search API-based indexer. Islandora already uses Search API to push (meta)data to Solr. It seems that we could use similar tooling to push to fcrepo and blazegraph. Drupal already knows how to serialize the repository item data as json-ld, and any indexing to external stores (fcrepo, blazegraph) can then use Drupal alter functions to allow implementations to modify/augment the data as needed. We also gain Search API UI for initiating a reindex etc. Also, we can add a query UI in due course, e.g. to do SPARQL against Blazegraph, or Fuseki, or whatever.

[joecorall]

@kayakr - I prefer your Search API-based approach for this.

I think we could start the implementation by just focusing on a search_api_fedora Drupal module that refactors Milliner using Search API plugin types.

Once that module is complete, we should be able to deprecate milliner and crayfish. We could then focus on a similar blazegraph/triplestore Search API module, but I do not believe that is required in order to deprecate crayfish and milliner.

[joecorall]

This is interesting and related to the conversation around blazegraph indexing (which should probably be a separate issue than this, but wanted to note this since I just came across it) https://www.drupal.org/project/triplestore_indexer