Using Guzzle promises asyncronously - php

Question

I am attempting to use guzzle promises in order to make some http calls, to illustrate what I have, I have made this simple example where a fake http request would take 5 seconds:
$then = microtime(true);
$promise = new Promise(
function() use (&$promise) {
//Make a request to an http server
$httpResponse = 200;
sleep(5);
$promise->resolve($httpResponse);
});
$promise2 = new Promise(
function() use (&$promise2) {
//Make a request to an http server
$httpResponse = 200;
sleep(5);
$promise2->resolve($httpResponse);
});
echo 'PROMISE_1 ' . $promise->wait();
echo 'PROMISE_2 ' . $promise2->wait();
echo 'Took: ' . (microtime(true) - $then);
Now what I would want to do is start both of them, and then make both echo's await for the response. What actually happens is promise 1 fires, waits 5 seconds then fires promise 2 and waits another 5 seconds.
From my understanding I should maybe be using the ->resolve(); function of a promise to make it start, but I dont know how to pass resolve a function in which I would make an http call

Answer 1

By using wait() you're forcing the promise to be resolved synchronously: https://github.com/guzzle/promises#synchronous-wait
According to the Guzzle FAQ you should use requestAsync() with your RESTful calls:
Can Guzzle send asynchronous requests?
Yes. You can use the requestAsync, sendAsync, getAsync, headAsync,
putAsync, postAsync, deleteAsync, and patchAsync methods of a client
to send an asynchronous request. The client will return a
GuzzleHttp\Promise\PromiseInterface object. You can chain then
functions off of the promise.
$promise = $client->requestAsync('GET', 'http://httpbin.org/get');
$promise->then(function ($response) {
echo 'Got a response! ' . $response->getStatusCode(); });
You can force an asynchronous response to complete using the wait()
method of the returned promise.
$promise = $client->requestAsync('GET', 'http://httpbin.org/get');
$response = $promise->wait();

Answer 2

This question is a little old but I see no answer, so I'll give it a shot, maybe someone will find it helpful.
You can use the function all($promises).
I can't find documentation about this function but you can find its implementation here.
The comment above this function starts like this:
Given an array of promises, return a promise that is fulfilled when all the items in the array are fulfilled.
Sounds like what you are looking for, so you can do something like this:
$then = microtime(true);
$promises = [];
$promises[] = new Promise(
function() use (&$promise) {
//Make a request to an http server
$httpResponse = 200;
sleep(5);
$promise->resolve($httpResponse);
});
$promises[] = new Promise(
function() use (&$promise2) {
//Make a request to an http server
$httpResponse = 200;
sleep(5);
$promise2->resolve($httpResponse);
});
all($promises)->wait();
echo 'Took: ' . (microtime(true) - $then);
If this function isn't the one that helps you solve your problem, there are other interesting functions in that file like some($count, $promises), any($promises) or settle($promises).

Answer 3

You can use the function Utils::all($promises)->wait();
Here is code example for "guzzlehttp/promises": "^1.4"
$promises = [];
$key = 0;
foreach(something...) {
$key++;
$promises[$key] = new Promise(
function() use (&$promises, $key) {
// here you can call some sort of async operation
// ...
// at the end call ->resolve method
$promises[$key]->resolve('bingo');
}
);
}
$res = Utils::all($promises)->wait();
It is important that your operation in promise must be non-blocking if you want to get concurrent workflow. For example, sleep(1) is blocking operation. So, 10 promises with sleep(1) - together are going to wait 10 sec anyway.