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@startuml

title Read flow for Secondary NodeStore
autonumber
hide footbox

participant "NodeStore\nClient" as NS
participant "Document\nNodeStore" as DNS
database "Cache"
database "Secondary Store" as SS
database Mongo

NS -> DNS : Read /a/b@r1

DNS -> SS : Read /a/b@r1
alt Found in Secondary Store
  SS -> DNS
  note over Cache
     Secondary Store has nodes under
     /a/b for revisions <= r1
  end note
  DNS -> NS : Read done from \nSecondary Store
  note left
      Further reads
      of children under
      /a/b would be done
      from Secondary Store
  end note
else Not in Secondary Store
  SS -> DNS :
  DNS -> Cache : Try to read from cache \n else load from Mongo
  alt Found in cache
   Cache -> DNS    : /a/b@r1 already in cache
   DNS -> NS       : Read done \n from memory cache
   else Not found in cache
    Cache -> Mongo : Read 2:/a/b from Mongo
    Mongo -> Cache : Return 2:/a/b
    Cache -> DNS   : Construct /a/b@r1\n and cache it
    DNS -> NS      : Read done \n from Mongo
    end
end

@enduml