Detailed explanation of PHP coroutines: Go + Chan + Defer

PHP coroutine: Go Chan Defer

Swoole4 provides a powerful CSP# for the PHP language ##Coroutine programming mode. The bottom layer provides 3 keywords, which can easily implement various functions. The PHP coroutine

syntax provided by

• Swoole4 is borrowed from Golang, and I would like to express my sincere thanks to the GO development team Tribute
• PHP SwooleCoroutines can complement Golang very well. Golang: static language, rigorous, powerful and good in performance, PHP Swoole: dynamic language, flexible, simple and easy to use

This article is based on

Swoole-4.2. 9 and PHP-7.2.9 version

Keywords

• go: Create a coroutine
• chan: Create a channel
• defer: Delay task, executed when the coroutine exits, first in, last out

This The underlying implementation of

3 functions are all memory operations, without any IO resource consumption. Just like PHPArray is very cheap. You can use it directly if necessary. This is different from socket and file operations. The latter need to apply for ports and file descriptors from the operating system, and reading and writing may cause blocking IO waiting.

Recommended learning: "

PHP Video Tutorial"

Coroutine Concurrency

Use the

go function to make a Functions are executed concurrently. During the programming process, if a certain piece of logic can be executed concurrently, it can be placed in the gocoroutine for execution.

Sequential execution

function test1() 
{
    sleep(1);
    echo "b";
}
    
function test2() 
{
    sleep(2);
    echo "c";
}

test1();
test2();

Execution results:

htf@LAPTOP-0K15EFQI:~$ time php b1.php
bc
real    0m3.080s
user    0m0.016s
sys     0m0.063s
htf@LAPTOP-0K15EFQI:~$

In the above code,

test1 and test2 will be executed sequentially, which requires3It takes seconds to complete the execution.

Concurrent execution

Using

go to create a coroutine can make the two functions test1 and test2 become concurrent executions .

Swoole\Runtime::enableCoroutine();

go(function () 
{
    sleep(1);
    echo "b";
});
    
go(function () 
{
    sleep(2);
    echo "c";
});

Swoole\Runtime::enableCoroutine()The function is to use the stream, sleep,# provided by PHP ##pdo, mysqli, redis and other functions switch from synchronous blocking to asynchronous coroutine IOExecution results:

bchtf@LAPTOP-0K15EFQI:~$ time php co.php
bc
real    0m2.076s
user    0m0.000s
sys     0m0.078s
htf@LAPTOP-0K15EFQI:~$

You can see that it only took

2

seconds to complete the execution.

The sequential execution time is equal to the sum of the execution time of all tasks:

t1 t2 t3...
• The concurrent execution time is equal to the execution time of all tasks The maximum value:
max(t1, t2, t3, ...)
Coroutine communication

With

go

key After the word, concurrent programming is much simpler. At the same time, it brings new problems. If there are 2 coroutines executing concurrently, and another coroutine needs to rely on the execution results of these two coroutines, how to solve this problem? The answer is to use a channel (

Channel

). You can create a channel by using new chan in the Swoole4 coroutine. A channel can be understood as a queue with its own coroutine scheduling. It has two interfaces push and pop:

push
• : writes content to the channel, if it is full, it It will enter the waiting state and automatically recover when there is space
pop
• : Read the content from the channel. If it is empty, it will enter the waiting state and automatically recover when there is data
Using channels can easily achieve

Concurrency management

.

$chan = new chan(2);

# 协程1
go (function () use ($chan) {
    $result = [];
    for ($i = 0; $i < 2; $i++)
    {
        $result += $chan->pop();
    }
    var_dump($result);
});

# 协程2
go(function () use ($chan) {
   $cli = new Swoole\Coroutine\Http\Client('www.qq.com', 80);
       $cli->set(['timeout' => 10]);
       $cli->setHeaders([
       'Host' => "www.qq.com",
       "User-Agent" => 'Chrome/49.0.2587.3',
       'Accept' => 'text/html,application/xhtml+xml,application/xml',
       'Accept-Encoding' => 'gzip',
   ]);
   $ret = $cli->get('/');
   // $cli->body 响应内容过大，这里用 Http 状态码作为测试
   $chan->push(['www.qq.com' => $cli->statusCode]);
});

# 协程3
go(function () use ($chan) {
   $cli = new Swoole\Coroutine\Http\Client('www.163.com', 80);
   $cli->set(['timeout' => 10]);
   $cli->setHeaders([
       'Host' => "www.163.com",
       "User-Agent" => 'Chrome/49.0.2587.3',
       'Accept' => 'text/html,application/xhtml+xml,application/xml',
       'Accept-Encoding' => 'gzip',
   ]);
   $ret = $cli->get('/');
   // $cli->body 响应内容过大，这里用 Http 状态码作为测试
   $chan->push(['www.163.com' => $cli->statusCode]);
});

Execution results:

htf@LAPTOP-0K15EFQI:~/swoole-src/examples/5.0$ time php co2.php
array(2) {
  ["www.qq.com"]=>
  int(302)
  ["www.163.com"]=>
  int(200)
}

real    0m0.268s
user    0m0.016s
sys     0m0.109s
htf@LAPTOP-0K15EFQI:~/swoole-src/examples/5.0$

go

is used here to create 3 coroutines, coroutines 2 and coroutines Cheng 3 requests the homepages of qq.com and 163.com respectively. Coroutine 1 needs to get the result of Http request. chan is used here to achieve concurrency management.

Coroutine

1
• Loop twice to pop the channel, because the queue is empty, it will enter the waiting stateCoroutine
2
• After the execution of the coroutine 3 is completed, the data will push. The coroutine 1 gets the result and continues to execute
Delayed tasks

In coroutine programming, you may need to automatically execute some tasks and clean up when the coroutine exits. Similar to

register_shutdown_function

of PHP, it can be implemented using defer in Swoole4. <pre class="brush:php;toolbar:false">Swoole\Runtime::enableCoroutine(); go(function () {     echo &quot;a&quot;;     defer(function () {         echo &quot;~a&quot;;     });     echo &quot;b&quot;;     defer(function () {         echo &quot;~b&quot;;     });     sleep(1);     echo &quot;c&quot;; });</pre>Execution results:

htf@LAPTOP-0K15EFQI:~/swoole-src/examples/5.0$ time php defer.php
abc~b~a
real    0m1.068s
user    0m0.016s
sys     0m0.047s
htf@LAPTOP-0K15EFQI:~/swoole-src/examples/5.0$

Conclusion

Swoole4

The Go Chan Defer provided isPHP It brings a new CSP concurrent programming model. Flexible use of various features provided by Swoole4 can solve the design and development of various complex functions at work.

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