Redis 4.x Cookbook

How to do it...

To understand Redis transactions, there is a scenario where we are going to organize a coupon codes seckilling, a quick sell out online, for a certain restaurant in Relp. There are only five coupon codes for this seckilling and we have a key, counts:seckilling, as a counter to hold the count of available coupon codes.

Here is the pseudo-code for this counter implementation:

//Initiate the count of coupon codes: 
SET("counts:seckilling",5);   
 
Start decreasing the counter: 
WATCH("counts:seckilling");   
count = GET("counts:seckilling"); 
MULTI();  
if count > 0 then 
           DECR("counts:seckilling",1); 
           EXEC();   
           if ret != null then 
                   print "Succeed!" 
              else 
                   print "Failed!" 
else 
  DISCARD();   
print "Seckilling Over!"