Efficiency: Taking a lock saves you from unnecessarily doing the same work twice (e.g. some expensive computation).
e.g. If the lock fails and two nodes end up doing the same piece of work, the result is a minor increase in cost (you end up paying 5 cents more to AWS than you otherwise would have)
e.g. SNS scenarios: A minor inconvenience (e.g. a user ends up getting the same email notification twice).
e.g. eCommerce website inventory control
Correctness: Taking a lock prevents concurrent processes from stepping on each othersβ toes and messing up the state of your system. If the lock fails and two nodes concurrently work on the same piece of data, the result is a corrupted file, data loss, permanent inconsistency, the wrong dose of a drug administered to a patient, or some other serious problem.
Requirementss
Exclusive
Avoid deadlock
High available
Reentrant
Comparison
Approach
Pros
Cons
Database
Easy to understand
High pressure on DB
Redis
Easy to understand
Not support blocking
Zookeeper
Support blocking
Rely on Zookeeper, high complexity
Curator
Easy to use
Rely on Zookeeper,
Redisson
Easy to use, support blocking
Usage example in oversell
Case 1: Subtract purchased count in program and update database to target count