What Is Two-Phase Commit (2PC)?

Let us enlighten and amuse you with our explanation of the Two-Phase Commit (2PC). Let's pretend you and your pals are in a restaurant and need to order something to share. One of your pals objects to the lasagna just as you're about to serve it. Cheese allergies make lasagna unappealing. What are your next steps? Well, that's where two-party coordination comes in (also known as "coordinator"). This person has an ultimate say in what gets ordered. The organizer begins by polling the table, "Are you comfortable ordering the lasagna?" You are now in the "prepare" phase of 2PC, the first of its three stages. During this stage, everyone at the table answers the coordinator's questions with a "yes" or "no" to demonstrate that they are friends. If all parties are on board, the coordinator will go on to the "commit" phase. The coordinator cancels the deal if even a single person says "no," so you'll have to choose another option. The coordinator gives the ultimate go-ahead in the "commit" step, at which point everyone involved says something like, "Okay, let's order the lasagna". Everybody who had anything to do with the exchange needs to double-check their records, just like you're all writing this down on the menu. What if a friend claims they filmed it, only to backtrack and admit they were wrong? To ensure that the transaction is documented accurately and everyone involved is on the same page, a "write-ahead log" is used. There you have it: a summary of two-party negotiation (2PC). The protocol guarantees that either all parties to a transaction will commit to it or none will, thus eliminating the possibility of contradictions. It's the equivalent of reaching a consensus and getting everyone on board with a plan. That said, keep 2PC in mind the next time you and your pals want to settle on a dining establishment. It's a simple method to ensure nobody is unhappy or has a terrible impression.