KolasuClient cannot be shared between threads

[alessiostalla]

In particular storeTree calls nodeConverter.clearNodesMapping() and that causes NPEs if other concurrent operations are using the mappings. Apart from that, in general, since the converter's node mappings are maps with no explicit provisions for multithreading, spurious errors may occur.

Of course a workaround is to create a new client for each thread, but that requires re-registering all the languages, we don't have a way to cache and reuse those.

[alessiostalla]

At a minimum, this should be documented.

[ftomassetti]

Would this be solved by making the nodeConverter thread-safe?

[alessiostalla]

No because it assumes mappings aren't cleared during its other operations