Two-Phase Commit Protocol

The Two-Phase Commit Protocol is a distributed algorithm used in computer science to ensure the atomicity of transactions across multiple nodes in a distributed system. In a distributed system, where data is stored and processed on multiple machines, it is crucial to maintain consistency and ensure that all nodes agree on the outcome of a transaction.

The Two-Phase Commit Protocol achieves this by breaking down the transaction into two distinct phases: the prepare phase and the commit phase. In the prepare phase, the coordinator node sends a message to all participant nodes, asking them to prepare to commit the transaction. Each participant node then checks if it is able to commit the transaction successfully, and responds to the coordinator with a vote - either "yes" if it can commit, or "no" if it cannot.

Once the coordinator receives all the votes from the participant nodes, it decides whether to proceed with the commit phase or abort the transaction. If all participant nodes vote "yes," the coordinator sends a commit message to all nodes, instructing them to go ahead and commit the transaction. If any participant node votes "no," or if the coordinator encounters a failure, the coordinator sends an abort message to all nodes, instructing them to roll back the transaction.

The Two-Phase Commit Protocol ensures that all nodes in a distributed system agree on the outcome of a transaction, either committing it successfully or rolling it back completely. This guarantees the atomicity of transactions, meaning that either the entire transaction is completed successfully, or no changes are made at all. While the Two-Phase Commit Protocol is effective in ensuring consistency and reliability in distributed systems, it can introduce latency and performance overhead due to the need for coordination among multiple nodes.