Redis implements optimistic lock

Pessimistic locking ： I think it's going to go wrong all the time , Lock whatever you do , Affect performance .

Optimism lock ： I don't think anything will go wrong at any time , So don't lock it , When updating, judge whether the data has been modified .

redis Realization ：

Access thread 1

# 0 moment 
set in 100
# 1 moment 
set out 0
# 2 moment 
watch in
# 3 moment 
multi
# 4  moment 
decrby in 20
# 5 moment 
incrby out 20
# 6 moment 
exec
....

# 10 moment 
set in 1000

Access thread 2：

#  moment 7
watch in
#  moment 8
decrby in 10
#  moment 9
incrby out 10
....
#  moment 11
exec
#  At this time, the transaction execution fails 

have access to watch Achieve optimistic lock , Before updating the value , Will get and compare this value , Be similar to version Field .

If you fail , Then you can execute unwatch, And use... Again watch To monitor .