for example, the ticket grabbing rule, there is a ticket in the library, two requests come in at the same time, how to make the first request execute and then execute the second one, so that the result of the second request is the result of the first request operation?
redis is fine, but for message queues, professionals can use rabbitMQ
rabbitMQ. There is a queue square in which messages (tickets) are stored. If a request comes, messages (tickets) in the square can be distributed to the request (consumer)
for example, a ticket numbered '12306' is stored in the database, and a 12306
A comes first in the queue. The queue sends this 12306 to A. A took this message to operate the database
B came, at this time A may not have left, because the frequency is very fast, but there are no tickets in the queue, and then the queue tells B that there are no tickets left. B just go back first.
you don't have to be first-in, first-out, first-out, first-in, first-out, first-
can be implemented using koa middleware.
let app = require ("koa");
app.use (async (ctx,next) = > {
await next (); / / execute the first request
/ / execute the second request
})
the database is locked.
try to forward requests from each API to the same object module when listening for related requests. When executing, the module only needs to implement a list to store all requests, then execute them sequentially and then call back. Of course, this can encapsulate a layer of Promise on the outside.
to put it simply, this data structure allows you to store values in it and pass a callback function. When it is executed, it will only be executed by Synchronize and executed in turn, and the result will be returned through a callback. Wrap it with Promise.
Today, my brain is a little cold. After writing, I found that there seems to be some places that haven't turned around. For example, I have to re-use callback and Promise encapsulation for Mao in Synchronize mode. However, the scheme mentioned above should be achievable, as I did when I controlled concurrency.
this needs to be implemented in mq and simply in DB. Other schemes can only be implemented in one process, but not with more than one.
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