What is the purpose of the @Transactional(propagation = Propagation.REQUIRES_NEW)?

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Introduction

In Spring's transaction management, the @Transactional annotation is used to define the transaction boundary for methods that need to participate in a transaction. One of the most useful attributes of @Transactional is propagation, which defines how transactions should behave when multiple transactional methods are involved.

When you set the propagation level to Propagation.REQUIRES_NEW, it tells Spring to suspend the current transaction (if one exists) and start a new transaction for the method. This can be helpful in scenarios where you want to ensure that a particular operation is executed within its own independent transaction, regardless of the outer transaction’s success or failure.

In this guide, we'll explore the purpose of @Transactional(propagation = Propagation.REQUIRES_NEW), how it works, and when to use it.

Purpose of @Transactional(propagation = Propagation.REQUIRES_NEW)

The Propagation.REQUIRES_NEW setting in the @Transactional annotation is used when you need to force a new transaction to start, suspending any existing transaction (if present) for the method being executed.

Key Characteristics:

  • Suspends the current transaction: If there is an active transaction, it is suspended, and a new transaction is started for the method that is annotated with @Transactional(propagation = Propagation.REQUIRES_NEW).
  • Independent Transaction: The method is executed in its own new transaction, and it does not depend on the outcome of the existing transaction.
  • Transaction Isolation: This behavior isolates the inner transaction from the outer transaction, meaning that changes made in the inner transaction are not affected by the outer transaction’s commit or rollback.

Use Case:

  • Nested Transactions: You may need a method to execute in its own independent transaction, regardless of the outer transaction’s result. For example, if you want to perform an operation (like logging or auditing) that should succeed independently of the main business logic transaction.
  • Rolling back a specific operation: If you want to ensure that a specific operation can fail or succeed independently, even if the outer transaction fails.

Example of @Transactional(propagation = Propagation.REQUIRES_NEW)

Here’s a simple example to demonstrate the usage of Propagation.REQUIRES_NEW:

Example: Independent Transaction for Logging

Consider an e-commerce system where you want to ensure that user activity is always logged in a separate transaction, regardless of whether the main transaction (like a purchase) succeeds or fails.

Explanation:

  • The placeOrder method starts a transaction, and the order is saved to the repository. If anything goes wrong within this method, the transaction will be rolled back, including the save operation.
  • However, the logOrderActivity method is annotated with @Transactional(propagation = Propagation.REQUIRES_NEW). This means the logging is performed in a new transaction, independent of the outer transaction (placeOrder). Even if the placeOrder transaction fails and rolls back, the logging will still be committed because it’s in a separate transaction.

Example with Nested Transactions:

In a case where you have nested business logic and you want to ensure that certain operations (like creating records in different tables) always succeed or fail independently:

In this case, even if the payment transaction fails and rolls back, the notification is sent in a separate transaction and will not be rolled back.

When to Use Propagation.REQUIRES_NEW

You would typically use @Transactional(propagation = Propagation.REQUIRES_NEW) when:

  1. Independent Transactions: You need a specific method to execute in its own isolated transaction, independent of the parent transaction.
    • For example, when logging or auditing data that should always be persisted, even if the main transaction fails.
  2. Transaction Suspension: You want to suspend the current transaction temporarily and start a new one, typically for specific actions that need to be isolated.
  3. Multiple Data Sources: You may need to handle operations across different data sources where the failure of one should not affect the other. For example, a primary database and a logging database.
  4. Rollback Scenarios: You want one part of the transaction (such as payment processing) to be rolled back if there’s an error, but other actions (such as sending notifications or logging) should proceed independently and not be affected.

Key Considerations

  • Nested Transactions: Although @Transactional(propagation = Propagation.REQUIRES_NEW) suspends the current transaction and starts a new one, Spring does not support real nested transactions. That is, the inner transaction cannot be part of the outer transaction in terms of rollback behavior. If an inner transaction fails, it will not automatically trigger a rollback of the outer transaction.
  • Performance Impact: Starting a new transaction can introduce overhead due to the need to manage multiple transactions, especially in high-throughput systems. It is important to use REQUIRES_NEW judiciously, as it can increase the complexity and resource usage of the system.
  • Isolation: REQUIRES_NEW provides a higher degree of transaction isolation because it isolates the inner transaction from the outer one. This is beneficial in cases where you need to ensure certain operations always succeed independently.

Conclusion

The @Transactional(propagation = Propagation.REQUIRES_NEW) annotation in Spring is used to execute a method in its own independent transaction, suspending any current transaction. This is particularly useful in scenarios where you need to isolate certain operations, such as logging, notifications, or certain business logic, from the success or failure of the main transaction.

By using REQUIRES_NEW, Spring provides flexibility for more complex transaction management patterns, ensuring that certain operations are always executed, even if other parts of the system fail or need to be rolled back.

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