Redis transaction

redis Business Complete... Is not supported acid Mechanism ,redis The process of transaction is divided into team formation and execution , An error occurred in a command in the process of forming a team , Then all errors are reported , An error occurred during execution , Still carry on , In addition to executing failed commands , Carry on , No, Transaction isolation level The concept of

Locking mechanism

Here is to redis Based on a single server , Lock is divided into optimistic lock and pessimistic lock

Optimism lock

Optimistic locks are distinguished by version numbers ,redis Transaction monitoring key, If I found key The version number before and after changes , Then the transaction execution fails , and redis The lock of a transaction is an optimistic lock

Pessimistic locking

Nothing to say. , Total occlusion , Native redis Can't achieve

Monitor one at a time key, Open two transactions , When the transaction is executed key Version number of changed , Then the transaction execution fails

Defects of two locking mechanisms

Optimism lock ： In a highly concurrent environment , It will lead to inventory problems （ Because of the high concurrency key The version of is modified by multiple transactions , Therefore, the competition will lead to the failure of transaction execution ）

Pessimistic locking ： Insufficient concurrency