Tarantool: Version Comparison

Tarantool uses one single thread for processing all transactions of a database instance, which is called 'transaction processor thread'. Thus the design is *lock-free*. Transactions occur in *fibers* on that single thread. A fiber is a set of instructions that may contain “yield” signals (yield can be either explicit or implicit, e.g., system calls). The transaction processor thread will execute all computer instructions until a yield, and then schedule a switch to another potentially ready fiber. This scheduling scheme is called *cooperative scheduling*. It means that unless a running fiber deliberately yields control, it cannot be preempted by other fibers. Thus, a transaction's author has the responsibility not to write long-running computations without a yield. When transaction commits, a yield happens and changes are written to WAL. A simple optimistic scheduler is used: the first transaction to commit wins. Any active transaction that has read a value modified by a committed transaction will be aborted. Moreover, Tarantool's cooperative scheduler implementation ensures that, in absence of yields, a multi-statement transaction is not preempted and thus will never be aborted.

Tarantool uses one single thread for processing all transactions of a database instance, which is called 'transaction processor thread'. Thus the design is **lock-free**. Transactions occur in **fibers** on that single thread. A fiber is a set of instructions that may contain “yield” signals (yield can be either explicit or implicit, e.g., system calls). The transaction processor thread will execute all computer instructions until a yield, and then schedule a switch to another potentially ready fiber. This scheduling scheme is called **cooperative scheduling**. It means that unless a running fiber deliberately yields control, it cannot be preempted by other fibers. Thus, a transaction's author has the responsibility not to write long-running computations without a yield. When transaction commits, a yield happens and changes are written to WAL. A simple optimistic scheduler is used: the first transaction to commit wins. Any active transaction that has read a value modified by a committed transaction will be aborted. Moreover, Tarantool's cooperative scheduler implementation ensures that, in absence of yields, a multi-statement transaction is not preempted and thus will never be aborted.