- A database transaction is a unit of work performed within a database management system. It is often composed of multiple operations (like inserts, updates, or deletes) that need to be executed together as a whole.
- A transaction typically ends with a commit (save changes) or a rollback (revert to the previous state).
- ACID properties ensure that database transactions are processed reliably:
- Atomicity: Ensures that all operations within a transaction are completed; if one operation fails, the entire transaction fails.
- Consistency: Ensures that a transaction brings the database from one valid state to another.
- Isolation: Ensures that transactions are executed in isolation from one another, preventing them from affecting each other's outcome.
- Durability: Once a transaction is committed, the changes are permanent, even in the event of a system failure.
- A protocol used to ensure atomicity in distributed systems where multiple nodes or services are involved in a transaction.
- Phase 1 (Prepare phase): The coordinator sends a request to all participants to prepare the transaction and report if they are ready to commit.
- Phase 2 (Commit phase): If all participants are ready, the coordinator sends a commit message. If any participant is not ready, a rollback is initiated to maintain consistency.
- A Saga is a pattern used to manage distributed transactions in a microservices architecture. Instead of using a two-phase commit, the saga pattern breaks the transaction into smaller, independent transactions.
- Each step of the saga has a corresponding compensation step to undo the work in case of failure.
- This pattern is useful in systems where 2PC would be too complex or slow.