FDK dataset harvester

The harvest process is triggered by messages from RabbitMQ with the routing key dataset.*.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. 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 all catalogs, resources with the type dcat:Catalog, blank node catalogs will be ignored. And then find all datasets each catalog contains, indicated by the predicate dcat:dataset and type dcat:Dataset, blank node datasets will be ignored. When all catalogs and datasets have been found a recursive function will create a graph with every contained triple for all catalogs and datasets.

The process will save metadata for both datasets and catalogs:

• 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 datasets, is the uri of the catalog it belongs to.
• removed - Only relevant for datasets, is set to true if the dataset 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 datasets.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

docker-compose up -d --build

Then in the terminal e.g.

% curl http://localhost:8081/catalogs

maven

docker-compose up -d rabbitmq
docker-compose up -d mongodb
mvn spring-boot:run -Dspring-boot.run.arguments="--spring.profiles.active=develop"

Then in another terminal e.g.

% curl http://localhost:8080/catalogs