DocumentNodeStore background read/update operations synchronized?

[Stefan Egli]

Hi,

Just realized that DocumentNodeStore background read and update operations
are synchronized ­ which basically makes them be executed sequentially ­
which somewhat works against OAK-2624.

@Marcel, @Chetan, wdyt, do they have to be synchronized? Could this not be a
bottleneck concurrency-wise?

Cheers,
Stefan