Error when chaining composite data souces

[pheyvaer]

Server configuration chains two composite data sources: composite data source A refers to composite data source B. Composite data source B refers to 1 HDT data source and 2 Turtle data sources.

The following SPARQL query executed via the ldf-clientagainst data source A results in a 502 after a certain amount of results have returned.

SELECT ?s ?n WHERE {?s <http://schema.org/name> ?n}

When executing this query directly against data source B or the HDT data source no error occurs.

[rubensworks]

The QPF branch contains fixes for this (831bd4231e46f8185c12d836904914efa5d82494) and other related issues (https://github.com/LinkedDataFragments/Server.js/commits/feature-qpf-latest/lib/datasources/CompositeDatasource.js).

@RubenVerborgh Should we backport these fixes? Or just wait until the 3.0.0 release?

[RubenVerborgh]

If we can backport with cherry-pick, I suggest to add this to develop. If not, @pheyvaer, is it a problem for you to work with the feature-qpf-branch?

[pheyvaer]

@RubenVerborgh At the moment it is not an urgent fix. I've circumvented the problem by replacing composite data source A by A' that refers to the data sources from B. So a bit of duplicate configuration is added, but it is not a showstopper.

[rubensworks]

@RubenVerborgh It won't be a clean cherry-pick, because the datasource is already graph-based at that point.

[RubenVerborgh]

Let's not do it then.