Distributed Databases Questions Medium
A distributed commit protocol in distributed databases is a mechanism used to ensure the consistency and durability of transactions across multiple nodes or sites in a distributed database system. It is responsible for coordinating the commit or rollback of a transaction across all participating nodes, ensuring that all changes made by the transaction are either permanently applied or rolled back in a coordinated manner.
The distributed commit protocol typically involves a two-phase commit (2PC) protocol, which consists of two phases: the prepare phase and the commit phase. In the prepare phase, the coordinator node sends a prepare request to all participating nodes, asking them to vote on whether they can commit or abort the transaction. Each participating node then responds with its vote, indicating whether it can commit or abort.
Once the coordinator receives all the votes, it decides whether to commit or abort the transaction based on the votes received. If all participating nodes vote to commit, the coordinator proceeds to the commit phase, where it sends a commit request to all nodes, instructing them to permanently apply the changes made by the transaction. On the other hand, if any participating node votes to abort, the coordinator sends an abort request to all nodes, instructing them to rollback the changes made by the transaction.
The distributed commit protocol ensures that all participating nodes reach a consensus on whether to commit or abort a transaction, thereby maintaining the atomicity and durability properties of distributed transactions. It handles failures and ensures that all nodes agree on the outcome of the transaction, even in the presence of network failures or node crashes.