Inconsistent reads from a HA Fuseki ensemble
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Hi @afs,
I realized now an issue running several HA Fuseki instances.
If my observation is correct a rdf-delta instance will return a query immediately even so its version is not up to date with respect to available patches. They are only starting a sync when the receive any kind of update or in pre-defined time intervals (this is at least my understanding).
If you run rdf-delta instances behind a load balancer which is most probably the way, most people would operate such a HA ensemble, this means you will get non-repeatable reads which can cause real issues (depending on the use case, of course).
Assume an application performs some operation based on he content of the triples in Fuseki, this will create issues.
This could be circumvented, if also queries would trigger a sync first. I could imagine, having a configuration parameter which allows to specify that also queries will trigger a sync.
What do you think?
Sorry just realized that synchronisation is also triggered when a rdf-delta instance is receiving a query.