[Fiware-tech-help] Questions regarding FIWARE setup (Orion, QL, CrateDB)

[Jakob Schnell]

Hey,

I'm currently setting up a FIWARE backend using docker, following the
"Querying Time Series Data" tutorial. I am a bit confused by how the FIWARE
components are supposed to behave on a restart of the system.

My setup consists of a Context Broker (Orion), QuantumLeap and a CrateDB for
data persistence, and I have created subscriptions for possible incoming
data. Assume that some data has been entered and persisted into CrateDB.

If I now restart the running docker containers, if I understood correctly,
Orion won't have any data anymore, the subscriptions will be gone and I haven't
found a way to get QuantumLeap to query the CrateDB for the data entered.

That would mean that I have to create all subscriptions anew and that I have to
query CrateDB directly for any "historical" data, which makes the system rather
clunky to use. All restarts would require manual interaction or some sort of
automating the creation of subscriptions, and all advantages of NGSI-v2 are
lost if CrateDB has to be queried directly.

Is there a way to persist subscriptions? Can I get QuantumLeap or Orion to
return the data saved in the CrateDB?

On a related note, could you explain what the purpose of the MongoDB connected
to Orion and the Redis connected to QuantumLeap is? Would the system work
without either of these?

Thanks for your help,
Best regards,
Jakob Schnell

-- 
Jakob Schnell
HeiGIT gGmbH
Heidelberg Institute for Geoinformation Technology at Heidelberg University

https://heigit.org | jakob.schnell at heigit.org | phone +49-6221-533 482

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