fdk-concept-harvester

The harvest process is triggered by messages from RabbitMQ with the routing key concept.*.HarvestTrigger, a message will call the method initiateHarvest in the class HarvesterActivity. The actual harvest will start when activitySemaphore has an available permit, when there are no available permits all messages will be queued by the semaphore.

The body of the trigger message has 3 relevant parameters:

• dataSourceId - Triggers the harvest of a specific source from fdk-harvest-admin
• publisherId - Triggers the harvest of all sources for the specified organization number.
• forceUpdate - Indicates that the harvest should be performed, even when no changes are detected in the source

A triggered harvest will download all relevant sources from fdk-harvest-admin, download everything from the source and try to read it as a RDF graph via a jena Model, TBX-sources will be transformed to RDF. If the source is successfully parsed as a jena Model it will be compared to the last harvest of the same source. The harvest process will continue if the source is not isomorphic to the last harvest or forceUpdate is true.

The actual harvest process will first find concepts, resources with the type skos:Concept, and collections, resources with the type skos:Collection, blank node concepts and collections will be ignored. A collection will also be generated from data about the source from fdk-harvest-admin, any concepts in the source that is not part of any collection, indicated by the predicate skos:member, will be added to this collection. When all collections and concepts have been found a recursive function will create a graph with every contained triple for all collections and concepts.

The process will save metadata for both concepts and collections:

• uri - The IRI for the resource, is used as the database id
• fdkId - The UUID used for the resource used in the context of FDK, is a generated hash of the uri if nothing else is set.
• isPartOf - Only relevant for concepts, is the uri of the collection it belongs to.
• removed - Only relevant for concepts, is set to true if the concept has been removed from the source.
• issued - The timestamp of the first time the resource was harvested
• modified - The timestamp of the last time a harvest of the resource found changes in the resource graph

All blank nodes will be skolemized in the resource graphs.

When all sources from the trigger has been processed a new rabbit message will be published with the routing key concepts.harvested, the message body will be a list of harvest reports, one report for each source from fdk-harvest-admin.

When the rabbit message has been published the semaphore permit is released and a new harvest trigger can be processed.

Requirements

• maven
• java 17
• docker
• docker-compose

Run tests

mvn verify

Run locally

docker-compose up -d
mvn spring-boot:run -Dspring-boot.run.profiles=develop

Then in another terminal e.g.

% curl http://localhost:8080/collections

Datastore

To inspect the MongoDB datastore, open a terminal and run:

docker-compose exec mongodb mongo
use admin
db.auth("admin","admin")
use conceptHarvester
db.collectionMeta.find()
db.conceptMeta.find()
db.turtle.find()