CODEWITHSUNDEEP
phplaravelconcurrencylaravel-5
Alex A.
Alex A.

Reputation: 39

Laravel events fired from different HTTP requests sync or async

Two HTTP requests received by a server with a PHP app that uses Laravel 5.2. Both fired the same type of Event. Both events intercepted by a single Listener.

Q1: Will events processed one after another in the order they were received by Listener (synchronously) or they will process concurrently?

Q2: Does there a way (or to do it in another way if Q1 answer is sync) synchronize any function between requests? I mean to be sure that no matter how many requests were received simultaneously, the function can be executed only by one request at the time

UPD. The issue what I'm trying to solve: my app should authenticate in a 3d party service. This is critical to establish only one session which will be used by other parts of the application. I want to store an access token for a session in DB. So this operation is not atomic: 1. Try to get token from DB. 2. If token does not exists: 2A. Authenticate and receive token. 2B. Store token in DB. 3. Return token

Upvotes: 0

Views: 703

Answers (1)

Flame
Flame

Reputation: 7580

Events are not a good way to fire functions in series. However, in PHP (and also Javascript) event callbacks are executed in the order their events have been triggered (so 1 -> 2 results in a -> b).

You'll have to elaborate on why you want to execute a function only by one request at a time. Likely you are looking for a locking or transaction mechanism, which is a RDBMS/SQL feature that prevents editting of records while they have not yet been saved. That way, when 2 requests happen to reach the same PHP function at the same time, you can have them wait on the database until a certain transaction completes, such that no overlap in reads or writes can take place.

See https://laravel.com/docs/5.8/queries#pessimistic-locking and https://laravel.com/docs/5.8/database#database-transactions for the Laravel implementation. There is more information on the MySQL website (assuming InnoDB is being used) :

https://dev.mysql.com/doc/refman/8.0/en/innodb-locking-reads.html

Upvotes: 1

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