Basic question 'bout reactphp

[RobertEcker]

Hi,

Sorry, for this - again - basic question about reactphp

To make my question more clear, I use this DNS lookup example:

<?php
$result = [];
$domains = ['domain1.com', 'domain2.xyz'];

foreach ($domains as $domain) {
    $result[] = dns_get_record($domain);
}

var_dump($result);

Can above example executed in parallel (to make it faster) with reactphp or not (and if yes, how with async? or event-loop? can you give me an additional hint)?
If I understand this stackoverflow post correctly, it can not (but I do not think so).

Thank you again.

[WyriHaximus]

That's easy, use react/dns

[RobertEcker]

Hi @WyriHaximus,

I know react/dns ... DNS was just an example ... it is more about a general question: how to execute own functions etc. in parallel with reactphp

[WyriHaximus]

Keep in mind that non of these functions can block, you'd still have to use non-blocking I/O functions for anything you do in here, but it comes down to:

$promises = [];
foreach (range(1, 13) as $i) {
    $promises[] = (async(function (int $i) {
        return $i;
    }))($i);
}

var_export(await($promises));

[RobertEcker]

thank you for the example
regarding "non of these functions can block": i do not fully understand because "dns_get_record" (in my example) blocks the next one/ones (because of waiting of the response) - or did you mean your example (then it is clear)

[WyriHaximus]

I meant functions like dns_get_record will block the event loop and thus everything else running in it. Which is why I suggested using react/dns. Let me rewrite your initial code with it, maybe that's clearer:

<?php
$result = [];
$domains = ['domain1.com', 'domain2.xyz'];

foreach ($domains as $domain) {
    $result[] = (async(function (string $domain) {
        return await($dns->resolve(domain));
    }))(domain);
}

var_dump(await($result));

That could be done simpler like this:

<?php
$result = [];
$domains = ['domain1.com', 'domain2.xyz'];

foreach ($domains as $domain) {
    $result[] = $dns->resolve(domain);
}

var_dump(await($result));

[RobertEcker]

Thank you again @WyriHaximus

That means the stackoverflow-post is correct? So reactphp is not forking processes to make it faster in general?

[RobertEcker]

ok maybe i should check react/dns how it is done there to make it possible for all functions?

[WyriHaximus]

We provide react/child-process to do such things, and I have a package or two allowing you to use child processes to run functions outside the current process. But that is not performant compared to staying in the current process alternatives that hook directly into the event loop.

The whole goal of reactphp is doing these things non-blocking at such a speed it looks like they are run in parallel.

[clue]

As @WyriHaximus pointed out, you can execute all blocking functions in a separate child process to avoid blocking the main process. For instance, you can use https://github.com/clue/reactphp-pq to execute the dns_get_record() function like this:

$executor = new Clue\React\Pq\Executor();
$dns_get_record = $executor->fun('dns_get_record');

$dns_get_record($domain)->then(function ($result) {
    var_dump($result);
}, function (Exception $e) {
    echo 'Error: ' . $e->getMessage() . PHP_EOL;
});

That said, I agree that this should usually be used as a last resort only as execution in child processes incurs some noticeable overhead (YMMV). For many common APIs, ReactPHP provides async alternatives that are implemented in pure PHP (see https://github.com/reactphp/reactphp/wiki/Users). For DNS queries, this would be the DNS component as suggested above.

I believe this has been answered, so I'm closing this for now. Please come back with more details if this problem persists and we can always reopen this 👍