π Protocol Overview β The Two-Phase Commit (2PC) protocol is a distributed algorithm used to ensure that a transaction is either committed or aborted across all participating nodes in a distributed system.
1οΈβ£ Prepare Phase β In this phase, the coordinator sends a prepare request to all participants. Each participant prepares to commit the transaction and logs the changes but does not commit yet. They respond with a vote to commit or abort.
2οΈβ£ Commit Phase β If all participants vote to commit, the coordinator sends a commit request to all. If any participant votes to abort, the coordinator sends an abort request. Participants then commit or abort based on the coordinator's decision.
βοΈ Consistency β 2PC ensures strict consistency across services by coordinating a global commit, making it suitable for scenarios requiring atomic transactions.
β οΈ Challenges β The protocol can introduce performance bottlenecks and single points of failure, especially if the coordinator fails during the process.
Protocol Phases
π Prepare Phase β The coordinator sends a prepare request to all participants. Participants prepare the transaction, log changes, and respond with a commit or abort vote.
π Commit Phase β If all votes are to commit, the coordinator sends a commit request. If any vote is to abort, an abort request is sent. Participants act based on the coordinator's final decision.
π Timing β The protocol requires careful timing and coordination to ensure all participants are ready to commit simultaneously.
π Logging β Participants log their actions during the prepare phase to ensure they can commit or abort as instructed.
π Rollback β If any participant votes to abort, the entire transaction is rolled back to maintain consistency.
Advantages and Disadvantages
β Advantage - Consistency β 2PC provides strict consistency, ensuring all nodes agree on the transaction outcome.
β Disadvantage - Performance β The protocol can cause performance bottlenecks due to the need for coordination and potential delays.
β Disadvantage - Single Point of Failure β The coordinator is a single point of failure, which can disrupt the entire transaction process if it fails.
β Advantage - Atomicity β Ensures that a transaction is fully completed or not at all, maintaining data integrity.
β Disadvantage - Complexity β Implementing 2PC can be complex, requiring careful management of transaction states and logs.
Use Cases
π¦ Bank Transfers β Ensures atomic transfer of funds between accounts in different banking systems.
ποΈ Distributed Databases β Coordinates commits across multiple database nodes to ensure data consistency.
π¦ Inventory Management β Synchronizes stock levels across different locations or systems to prevent overselling.
π³ Payment Processing β Ensures all parts of a payment transaction are completed or none at all.
π Financial Transactions β Used in scenarios where financial data integrity is critical and must be maintained across systems.
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