PHP - data access concurrency testing

Question

Imagine that you have interfaces which describe the data access layer of your application. You haven't decided yet what kind of storing mechanism you want to use, you just want to make sure, that whatever you choose, it will handle concurrent requests well. For that you have to write concurrency tests against those interfaces.

I think a schematic concurrency test should be something like this:

public function testMoneyIsNotLostByConcurrentTransfers(){
    $accountRepository = DataAccessLayer::getBankAccountRepository();
    $accountOfTom = $accountRepository->create(array(
        'owner' => 'Tom',
        'balance' => new Money(10000)
    ));
    $accountOfBob = $accountRepository->create(array(
        'owner' => 'Bob',
        'balance' => new Money(10000)
    ));
    $accountOfSusanne = $accountRepository->create(array(
        'owner' => 'Susanne',
        'balance' => new Money(10000)
    ));

    $this->concurrentExecution(
        function () use ($accountOfTom, $accountOfBob){
            $accountOfTom->transfer($accountOfBob, new Money(5000));
        },
        function() use ($accountOfTom, $accountOfSusanne){
            $accountOfSusanne->transfer($accountOfTom, new Money(5000));
        }
    );

    $this->assertEquals($accountOfTom->getBalanceAmount(), 10000);
    $this->assertEquals($accountOfBob->getBalanceAmount(), 15000);
    $this->assertEquals($accountOfSusanne->getBalanceAmount(), 5000);
}

Is it possible to write such tests, test runner in PHP? Or is there any existing tool which can help by concurrency testing in PHP?

Answer 1

I could not find any test runner for such concurrency tests. I found only paratest, which can run independent tests, like unit tests parallel.

According to PHP - parallel task runner the best option I think is using pthreads with debug_backtrace. I think it will be hard even with that. I am looking forward the installing problems, thread safety, resource sharing difficulties, backtrace bugs, etc... I will have a great time I am sure...:S

I found async calls in the pthreads examples.

If I ever manage to solve this, I will share it on github and add a link here. Until then...

update

I just realized that I don't need multi thread or multi process applications to test concurrency. For example I can start two transactions with 2 database connections from the same php file. What I need is add event triggering for the statements the db driver does, so I can add breakpoints and wait the other task wherever I want. File locking is just the same... So coroutines or some hand made multi tasking and statement logging is just enough...

Answer 2

Concurrency should be built into your saving mechanism, not the execution layer.

For example, if you are using SQL, instead of setting the variable use += and -=.