Solution to multi-threading problem in php fsockopen [Translation]

Solution to multi-threading problem in php fsockopen [Translation]_PHP Tutorial

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Release： 2016-07-21 15:22:55

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Question:
Is there a way to implement multi-threading in php?
Suppose you are writing a PHP application based on multiple servers. The ideal situation is to send requests to multiple servers at the same time, rather than one after another.
Is it possible?
Answer:
When someone wants to implement concurrency functions, they usually think of using fork or spawn threads, but when they find that PHP does not support multi-threading, they may change their minds and use some insufficient A good language, such as perl.
In fact, in most cases, you don't need to use fork or thread, and you will get better performance than using fork or thread.
Suppose you want to build a service to check n running servers to make sure they are still functioning normally. You might write code like this:

Copy code The code is as follows:

 
$hosts = array("host1.sample.com", "host2.sample.com", "host3.sample.com"); 
$timeout = 15; $status = array(); 
foreach ($hosts as $host) { 
$errno = 0; 
$errstr = ""; 
$s = fsockopen($host, 80, $errno, $errstr, $timeout); 
if ( $s) { 
$status[$host] = "Connectedn"; 
fwrite($s, "HEAD / HTTP/1.0rnHost: $hostrnrn"); 
do { 
$data = fread($s, 8192); 
if (strlen($data) == 0) { break; } 
$status[$host] .= $data; 
} while (true); fclose ($s); 
} else { 
$status[$host] = "Connection failed: $errno $errstrn"; 
} 
} 
print_r($status); 
?> 

It works fine, but extend this code to manage a large number of The server will take a long time.
So we have to abandon this code; we can establish an asynchronous connection - no need to wait for fsockopen to return connection status. PHP still needs to resolve the hostname (so it's more sensible to use the ip directly), but it will return immediately after opening a connection, and then we can connect to the next server.
There are two ways to achieve this; in PHP5, you can use the new stream_socket_client() function to directly replace fsocketopen(). For versions before PHP5, you need to do it yourself and use sockets extension to solve the problem.
The following is the solution in PHP5:

Copy the code The code is as follows:

 
 $hosts = array("host1.sample.com", "host2.sample.com", "host3.sample.com"); 
$timeout = 15; 
$status = array(); 
$sockets = array(); 
foreach ($hosts as $id => $host) { 
$s = stream_socket_client("$host:80", $errno, $errstr, $timeout,STREAM_CLIENT_ASYNC_CONNECT |STREAM_CLIENT_CONNECT); 
if ($s) { 
$sockets[$id] = $s; 
$status[$id] = "in progress"; 
} else { 
 $status[$id] = "failed, $errno $errstr"; 
} 
} 
while (count($sockets)) { 
$read = $write = $sockets; 
$n = stream_select($read, $write, $e = null, $timeout); 
if ($n > 0) { 
foreach ($read as $r) { 
$id = array_search($r, $sockets); 
$data = fread($r, 8192); 
if (strlen($data) == 0) { 
if ($status[$id] == "in progress") { 
$status[$id] = "failed to connect"; 
} 
fclose($r); 
unset($sockets[$id]); 
} else { 
$status[$id] .= $data; 
} 
} 
foreach ($write as $w) { 
$id = array_search($w , $sockets); 
fwrite($w, "HEAD / HTTP/1.0rnHost: " . $hosts[$id] . "rnrn"); 
$status[$id] = "waiting for response" ; 
} 
} else { 
foreach ($sockets as $id => $s) { 
$status[$id] = "timed out " . $status[$id]; 
} 
break; 
} 
} 
foreach ($hosts as $id => $host) { 
echo "Host: $hostn"; echo "Status: " . $status[$id] . "nn"; 
} 
?> 

We use stream_select() to wait for the connection event of sockets opening. stream_select() calls the system's select(2) function to work: the first three parameters are the arrays of streams you want to use; you can read, write and get exceptions from them (for the three parameters respectively). stream_select() can wait for an event to occur by setting the $timeout (seconds) parameter - when the event occurs, the corresponding socket data will be written to the parameters you passed in.
The following is the implementation of PHP 4.1.0 and later. If you have included sockets (ext/sockets) support when compiling PHP, you can use similar code as above, but you need to add the functions of the streams/filesystem function above. Implemented using ext/sockets function. The main difference is that we use the following function instead of stream_socket_client() to establish the connection:

Copy code The code is as follows:

 
// This value is correct for Linux, other systems have other values ​​
define('EINPROGRESS', 115); 
function non_blocking_connect($host, $port , &$errno, &$errstr, $timeout) { 
$ip = gethostbyname($host); 
$s = socket_create(AF_INET, SOCK_STREAM, 0); 
if (socket_set_nonblock($s) ) { 
$r = @socket_connect($s, $ip, $port); 
if ($r || socket_last_error() == EINPROGRESS) { 
$errno = EINPROGRESS; return $s; 
} 
} 
$errno = socket_last_error($s); 
$errstr = socket_strerror($errno); 
socket_close($s); 
return false; 
 } 
?> 

Now replace stream_select() with socket_select(), fread() with socket_read(), fwrite() with socket_write(), and socket_close( ) to replace fclose() to execute the script!
The advancement of PHP5 is that you can use stream_select() to process almost all streams - for example, you can use it to receive keyboard input by include STDIN and save it into an array, and you can also receive it from a pipe opened by proc_open() data.
If you want PHP4.3.x to have the function of processing streams, I have prepared a patch for you to make fsockopen work asynchronously. This patch is deprecated and will not appear in the officially released PHP version. I included the implementation of the stream_socket_client() function in the patch, through which you can make your script compatible with PHP5.