How to restrict observer node from doing any transaction

Question

need to implement corda node which is pure observer means which persist states but wont participate with other nodes for any transaction.

In order to acheive it i did followning thing:

Made 3 nodes as follow:

PartyA - Nodes contain cordApp jar including transactional flow, observerflow and Contract and states

PartyB - Nodes contain cordApp jar including transactional flow, observerflow and Contract and states

Observer - Nodes contain contract and State along with observer flow only.

On observer node all transactional nodes removed intentionally so that observer wont able to transact with other node.

After nodes start up, performed transaction from PartyA to PartyB by keeping Observer node as observer. It works perfectly.

Now i tried same thing from PartyA to observer and keep PartyB as observer. I expected transaction will get failed but transaction got committed on observer node even though observer node has no transactional flows.

When i tried to perform transaction from observer to PartyA then it gives error as no flow found which is expected.

Example i am using have ownable state and simple initiating flows are used.

My question is how one directional transaction worked with observer inspite of no flows on observer.

How can i prevent observer from not doing any transaction with other nodes, just act as pure observer.

Joel Joel · Accepted Answer · 2018-11-01T11:36:04

As of Corda 3, the node actually installs default flow responders when it starts up for the four following flows:

FinalityFlow
NotaryChangeFlow
ContractUpgradeFlow.Initiate
SwapIdentitiesFlow

This is done in AbstractNode.installCoreFlows:

private fun installCoreFlows() {
    installCoreFlow(FinalityFlow::class, ::FinalityHandler)
    installCoreFlow(NotaryChangeFlow::class, ::NotaryChangeHandler)
    installCoreFlow(ContractUpgradeFlow.Initiate::class, ::ContractUpgradeHandler)
    installCoreFlow(SwapIdentitiesFlow::class, ::SwapIdentitiesHandler)
}

Thus the observer node will still be able to receive and record transactions as part of calls to FinalityFlow.

In a future version of Corda, this default FinalityFlow handler will be removed. Nodes will have to explicitly create a flow that receives and stores a transaction, allowing you to implement the behaviour above.

How to restrict observer node from doing any transaction

1 Answers