corda / net.corda.flows / NotaryFlow / Service

Service

class Service : FlowLogic<Unit>

Checks that the timestamp command is valid (if present) and commits the input state, or returns a conflict if any of the input states have been previously committed.

Extend this class, overriding beforeCommit to add custom transaction processing/validation logic.

TODO: the notary service should only be able to see timestamp commands and inputs

Constructors

<init> Service(otherSide: Party, timestampChecker: TimestampChecker, uniquenessProvider: UniquenessProvider)

Checks that the timestamp command is valid (if present) and commits the input state, or returns a conflict if any of the input states have been previously committed.

Properties

otherSide val otherSide: Party
timestampChecker val timestampChecker: TimestampChecker
uniquenessProvider val uniquenessProvider: UniquenessProvider

Inherited Properties

logger val logger: Logger

This is where you should log things to.

progressTracker open val progressTracker: ProgressTracker?

Override this to provide a ProgressTracker. If one is provided and stepped, the framework will do something helpful with the progress reports. If this flow is invoked as a subflow of another, then the tracker will be made a child of the current step in the parent. If it's null, this flow doesn't track progress.

runId val runId: StateMachineRunId

Returns a wrapped UUID object that identifies this state machine run (i.e. subflows have the same identifier as their parents).

serviceHub val serviceHub: ServiceHub

Provides access to big, heavy classes that may be reconstructed from time to time, e.g. across restarts. It is only available once the flow has started, which means it cannnot be accessed in the constructor. Either access this lazily or from inside call.

stateMachine var stateMachine: FlowStateMachine<*>

Internal only. Reference to the Fiber instance that is the top level controller for the entire flow. When inside a flow this is equivalent to Strand.currentStrand. This is public only because it must be accessed across module boundaries.

Functions

beforeCommit open fun beforeCommit(stx: SignedTransaction): Unit

No pre-commit processing is done. Transaction is not checked for contract-validity, as that would require fully resolving it into a TransactionForVerification, for which the caller would have to reveal the whole transaction history chain. As a result, the Notary will commit invalid transactions as well, but as it also records the identity of the caller, it is possible to raise a dispute and verify the validity of the transaction and subsequently undo the commit of the input states (the exact mechanism still needs to be worked out).

call open fun call(): Unit

This is where you fill out your business logic. The returned object will usually be ignored, but can be helpful if this flow is meant to be used as a subflow.

Inherited Functions

getCounterpartyMarker open fun getCounterpartyMarker(party: Party): Class<*>

Return the marker Class which party has used to register the counterparty flow that is to execute on the other side. The default implementation returns the class object of this FlowLogic, but any Class instance will do as long as the other side registers with it.

receive open fun <R : Any> receive(receiveType: Class<R>, otherParty: Party): UntrustworthyData<R>

Suspends until the specified otherParty sends us a message of type receiveType.

fun <R : Any> receive(otherParty: Party): UntrustworthyData<R>

Suspends until the specified otherParty sends us a message of type R.

send open fun send(otherParty: Party, payload: Any): Unit

Queues the given payload for sending to the otherParty and continues without suspending.

sendAndReceive open fun <R : Any> sendAndReceive(receiveType: Class<R>, otherParty: Party, payload: Any): UntrustworthyData<R>

Serializes and queues the given payload object for sending to the otherParty. Suspends until a response is received, which must be of the given receiveType. Remember that when receiving data from other parties the data should not be trusted until it's been thoroughly verified for consistency and that all expectations are satisfied, as a malicious peer may send you subtly corrupted data in order to exploit your code.

fun <R : Any> sendAndReceive(otherParty: Party, payload: Any): UntrustworthyData<R>

Serializes and queues the given payload object for sending to the otherParty. Suspends until a response is received, which must be of the given R type.

subFlow open fun <R> subFlow(subLogic: FlowLogic<R>, shareParentSessions: Boolean = false): R

Invokes the given subflow. This function returns once the subflow completes successfully with the result returned by that subflows call method. If the subflow has a progress tracker, it is attached to the current step in this flow's progress tracker.

track fun track(): Pair<String, Observable<String>>?

Returns a pair of the current progress step, as a string, and an observable of stringified changes to the progressTracker.

Inheritors

ValidatingNotaryFlow class ValidatingNotaryFlow : Service

A notary commit flow that makes sure a given transaction is valid before committing it. This does mean that the calling party has to reveal the whole transaction history; however, we avoid complex conflict resolution logic where a party has its input states "blocked" by a transaction from another party, and needs to establish whether that transaction was indeed valid.