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## Summary This change deals with multiple issues: * Errors that occur during flow initialisation. * Errors that occur when handling the outcome of an existing flow error. * Failures to rollback and close a database transaction when an error occurs in `TransitionExecutorImpl`. * Removal of create and commit transaction actions around retrying a flow. ## Errors that occur during flow initialisation Flow initialisation has been moved into the try/catch that exists inside `FlowStateMachineImpl.run`. This means if an error is thrown all the way out of `initialiseFlow` (which should rarely happen) it will be caught and move into a flow's standard error handling path. The flow should then properly terminate. `Event.Error` was changed to make the choice to rollback be optional. Errors during flow initialisation cause the flow to not have a open database transaction. Therefore there is no need to rollback. ## Errors that occur when handling the outcome of an existing flow error When an error occurs a flow goes to the flow hospital and is given an outcome event to address the original error. If the transition that was processing the error outcome event (`StartErrorPropagation` and `RetryFlowFromSafePoint`) has an error then the flow aborts and nothing happens. This means that the flow is left in a runnable state. To resolve this, we now retry the original error outcome event whenever another error occurs doing so. This is done by adding a new staff member that looks for `ErrorStateTransitionException` thrown in the error code path of `TransitionExecutorImpl`. It then takes the last outcome for that flow and schedules it to run again. This scheduling runs with a backoff. This means that a flow will continually retry the original error outcome event until it completes it successfully. ## Failures to rollback and close a database transaction when an error occurs in `TransitionExecutorImpl` Rolling back and closing the database transaction inside of `TransitionExecutorImpl` is now done inside individual try/catch blocks as this should not prevent the flow from continuing. ## Removal of create and commit transaction actions around retrying a flow The database commit that occurs after retrying a flow can fail which required some custom code just for that event to prevent inconsistent behaviour. The transaction was only needed for reading checkpoints from the database, therefore the transaction was moved into `retryFlowFromSafePoint` instead and the commit removed. If we need to commit data inside of `retryFlowFromSafePoint` in the future, a commit should be added directly to `retryFlowFromSafePoint`. The commit should occur before the flow is started on a new fiber.
Corda
Corda is an open source blockchain project, designed for business from the start. Only Corda allows you to build interoperable blockchain networks that transact in strict privacy. Corda's smart contract technology allows businesses to transact directly, with value.
Features
- Smart contracts that can be written in Java and other JVM languages
- Flow framework to manage communication and negotiation between participants
- Peer-to-peer network of nodes
- "Notary" infrastructure to validate uniqueness and sequencing of transactions without global broadcast
- Enables the development and deployment of distributed apps called CorDapps
- Written in Kotlin, targeting the JVM
Getting started
- Read the Getting Started documentation
- Run the Example CorDapp
- Read about Corda's Key Concepts
- Follow the Hello, World! tutorial
Useful links
- Project Website
- Mailing List
- Documentation
- Stack Overflow Tag
- Slack Channel
- Meetups
- Training Courses
Contributing
Corda is an open-source project and contributions are welcome!
To find out how to contribute, please see our contributing docs.
License
Acknowledgements
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