corda / net.corda.core.flows / FlowLogic

FlowLogic

abstract class FlowLogic<out T>

A sub-class of FlowLogic implements a flow using direct, straight line blocking code. Thus you can write complex flow logic in an ordinary fashion, without having to think about callbacks, restarting after a node crash, how many instances of your flow there are running and so on.

Invoking the network will cause the call stack to be suspended onto the heap and then serialized to a database using the Quasar fibers framework. Because of this, if you need access to data that might change over time, you should request it just-in-time via the serviceHub property which is provided. Don't try and keep data you got from a service across calls to send/receive/sendAndReceive because the world might change in arbitrary ways out from underneath you, for instance, if the node is restarted or reconfigured!

Additionally, be aware of what data you pin either via the stack or in your FlowLogic implementation. Very large objects or datasets will hurt performance by increasing the amount of data stored in each checkpoint.

If you'd like to use another FlowLogic class as a component of your own, construct it on the fly and then pass it to the subFlow method. It will return the result of that flow when it completes.

If your flow (whether it's a top-level flow or a subflow) is supposed to initiate a session with the counterparty and request they start their counterpart flow, then make sure it's annotated with InitiatingFlow. This annotation also has a version property to allow you to version your flow and enables a node to restrict support for the flow to that particular version.

Constructors

<init>

FlowLogic()

A sub-class of FlowLogic implements a flow using direct, straight line blocking code. Thus you can write complex flow logic in an ordinary fashion, without having to think about callbacks, restarting after a node crash, how many instances of your flow there are running and so on.

Properties

logger

val logger: Logger

This is where you should log things to.

ourIdentity

val ourIdentity: Party

Specifies the identity to use for this flow. This will be one of the multiple identities that belong to this node. This is the same as calling ourIdentityAndCert.party.

ourIdentityAndCert

val ourIdentityAndCert: PartyAndCertificate

Specifies the identity, with certificate, to use for this flow. This will be one of the multiple identities that belong to this node.

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 e.g record to the audit service. 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 java.util.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.

Functions

call

abstract fun call(): T

This is where you fill out your business logic.

checkFlowPermission

fun checkFlowPermission(permissionName: String, extraAuditData: Map<String, String>): Unit

Flows can call this method to ensure that the active FlowInitiator is authorised for a particular action. This provides fine grained control over application level permissions, when RPC control over starting the flow is insufficient, or the permission is runtime dependent upon the choices made inside long lived flow code. For example some users may have restricted limits on how much cash they can transfer, or whether they can change certain fields. An audit event is always recorded whenever this method is used. If the permission is not granted for the FlowInitiator a FlowException is thrown.

flowStackSnapshot

fun flowStackSnapshot(): FlowStackSnapshot?

Returns a shallow copy of the Quasar stack frames at the time of call to flowStackSnapshot. Use this to inspect what objects would be serialised at the time of call to a suspending action (e.g. send/receive). Note: This logic is only available during tests and is not meant to be used during the production deployment. Therefore the default implementation does nothing.

getFlowInfo

fun getFlowInfo(otherParty: Party): FlowInfo

Returns a FlowInfo object describing the flow otherParty is using. With FlowInfo.flowVersion it provides the necessary information needed for the evolution of flows and enabling backwards compatibility.

initiateFlow

fun initiateFlow(party: Party): FlowSession

Creates a communication session with party. Subsequently you may send/receive using this session object. Note that this function does not communicate in itself, the counter-flow will be kicked off by the first send/receive.

persistFlowStackSnapshot

fun persistFlowStackSnapshot(): Unit

Persists a shallow copy of the Quasar stack frames at the time of call to persistFlowStackSnapshot. Use this to track the monitor evolution of the quasar stack values during the flow execution. The flow stack snapshot is stored in a file located in {baseDir}/flowStackSnapshots/YYYY-MM-DD/{flowId}/ where baseDir is the node running directory and flowId is the flow unique identifier generated by the platform.

receive

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

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

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

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

recordAuditEvent

fun recordAuditEvent(eventType: String, comment: String, extraAuditData: Map<String, String>): Unit

Flows can call this method to record application level flow audit events

send

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

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

sendAndReceive

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.

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.

subFlow

open fun <R> subFlow(subLogic: FlowLogic<R>): R

Invokes the given subflow. This function returns once the subflow completes successfully with the result returned by that subflow's 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(): DataFeed<String, String>?

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

waitForLedgerCommit

fun waitForLedgerCommit(hash: SecureHash): SignedTransaction

Suspends the flow until the transaction with the specified ID is received, successfully verified and sent to the vault for processing. Note that this call suspends until the transaction is considered valid by the local node, but that doesn't imply the vault will consider it relevant.

Inheritors

AbstractCashFlow

abstract class AbstractCashFlow<out T> : FlowLogic<T>

Initiates a flow that produces an Issue/Move or Exit Cash transaction.

Acceptor

abstract class Acceptor<in T> : FlowLogic<Void?>

Authorise

class Authorise : FlowLogic<Void?>

Authorise a contract state upgrade.

Buyer

class Buyer : FlowLogic<SignedTransaction>

CashConfigDataFlow

class CashConfigDataFlow : FlowLogic<CashConfiguration>

Flow to obtain cash cordapp app configuration.

Client

class Client : FlowLogic<List<TransactionSignature>>

A flow to be used by a party for obtaining signature(s) from a NotaryService ascertaining the transaction time-window is correct and none of its inputs have been used in another completed transaction.

CollectSignatureFlow

class CollectSignatureFlow : FlowLogic<List<TransactionSignature>>

Get and check the required signature.

CollectSignaturesFlow

class CollectSignaturesFlow : FlowLogic<SignedTransaction>

The CollectSignaturesFlow is used to automate the collection of counter-party signatures for a given transaction.

DataVendingFlow

sealed class DataVendingFlow : FlowLogic<Void?>

Deauthorise

class Deauthorise : FlowLogic<Void?>

Deauthorise a contract state upgrade. This will remove the upgrade authorisation from persistent store (and prevent any further upgrade)

FetchDataFlow

sealed class FetchDataFlow<T : NamedByHash, in W : Any> : FlowLogic<Result<T>>

An abstract flow for fetching typed data from a remote peer.

FinalityFlow

class FinalityFlow : FlowLogic<SignedTransaction>

Verifies the given transaction, then sends it to the named notary. If the notary agrees that the transaction is acceptable then it is from that point onwards committed to the ledger, and will be written through to the vault. Additionally it will be distributed to the parties reflected in the participants list of the states.

Instigator

abstract class Instigator<out S : ContractState, out T : ContractState, out M> : FlowLogic<StateAndRef<T>>

The Instigator assembles the transaction for state replacement and sends out change proposals to all participants (Acceptor) of that state. If participants agree to the proposed change, they each sign the transaction. Finally, Instigator sends the transaction containing all participants' signatures to the notary for signature, and then back to each participant so they can record it and use the new updated state for future transactions.

Primary

abstract class Primary : FlowLogic<SignedTransaction>

Abstracted bilateral deal flow participant that initiates communication/handshake.

ReceiveStateAndRefFlow

class ReceiveStateAndRefFlow<out T : ContractState> : FlowLogic<List<StateAndRef<T>>>

The ReceiveStateAndRefFlow should be called in response to the SendStateAndRefFlow.

ReceiveTransactionFlow

class ReceiveTransactionFlow : FlowLogic<SignedTransaction>

The ReceiveTransactionFlow should be called in response to the SendTransactionFlow.

ResolveTransactionsFlow

class ResolveTransactionsFlow : FlowLogic<List<SignedTransaction>>

Resolves transactions for the specified txHashes along with their full history (dependency graph) from otherSide. Each retrieved transaction is validated and inserted into the local transaction storage.

Secondary

abstract class Secondary<U> : FlowLogic<SignedTransaction>

Abstracted bilateral deal flow participant that is recipient of initial communication.

Seller

class Seller : FlowLogic<SignedTransaction>

Service

abstract class Service : FlowLogic<Void?>

A flow run by a notary service that handles notarisation requests.

SignTransactionFlow

abstract class SignTransactionFlow : FlowLogic<SignedTransaction>

The SignTransactionFlow should be called in response to the CollectSignaturesFlow. It automates the signing of a transaction providing the transaction: