Console
.
WriteLine
(
"The name of the bike is: "
+
value
+
"."
);
Note:
The following pattern is discouraged in favor of
the Redlock algorithm
which is only a bit more complex to implement, but offers better guarantees and is fault tolerant.
The command
SET resource-name anystring NX EX max-lock-time
is a simple way to implement a locking system with Redis.
A client can acquire the lock if the above command returns
OK
(or retry after some time if the command returns Nil), and remove the lock just using
DEL
.
The lock will be auto-released after the expire time is reached.
It is possible to make this system more robust modifying the unlock schema as follows:
Instead of setting a fixed string, set a non-guessable large random string, called token.
Instead of releasing the lock with
DEL
, send a script that only removes the key if the value matches.
This avoids that a client will try to release the lock after the expire time deleting the key created by another client that acquired the lock later.
An example of unlock script would be similar to the following:
if redis.call("get",KEYS[1]) == ARGV[1]
return redis.call("del",KEYS[1])
return 0
The script should be called with EVAL ...script... 1 resource-name token-value
Return information
If GET was not specified, any of the following:
Nil reply: Operation was aborted (conflict with one of the XX/NX options). The key was not set.
Simple string reply: OK: The key was set.
If GET was specified, any of the following:
Nil reply: The key didn't exist before the SET. If XX was specified, the key was not set. Otherwise, the key was set.
Bulk string reply: The previous value of the key. If NX was specified, the key was not set. Otherwise, the key was set.
If GET was not specified, any of the following:
Null reply: Operation was aborted (conflict with one of the XX/NX options). The key was not set.
Simple string reply: OK: The key was set.
If GET was specified, any of the following:
Null reply: The key didn't exist before the SET. If XX was specified, the key was not set. Otherwise, the key was set.
Bulk string reply: The previous value of the key. If NX was specified, the key was not set. Otherwise, the key was set.
Starting with Redis version 2.6.12: Added the EX, PX, NX and XX options.
Starting with Redis version 6.0.0: Added the KEEPTTL option.
Starting with Redis version 6.2.0: Added the GET, EXAT and PXAT option.
Starting with Redis version 7.0.0: Allowed the NX and GET options to be used together.
