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How to correctly use the curl_multi_close function to avoid memory leaks?
About the memory management issues and optimization methods of curl_multi_close
In PHP, cURL is a powerful tool for sending HTTP requests. However, when we use multiple concurrent requests, it becomes particularly important to manage the memory of those requests. Especially when concurrent requests are used with the curl_multi_* function family, the wrong resource release method can lead to memory leaks. curl_multi_close is a function that closes multiple cURL sessions, but if used improperly, it can still cause memory problems. This article will discuss how to correctly use curl_multi_close to avoid memory leaks, as well as some optimization methods.
PHP's cURL library provides a curl_multi_* function family for handling multiple concurrent requests. Common usages include:
curl_multi_init() : Initialize a cURL handle.
curl_multi_add_handle() : Adds the cURL handle to the multiple handle.
curl_multi_exec() : executes all cURL requests.
curl_multi_getcontent() : Get the response content of each request.
curl_multi_remove_handle() : Removes the completed request handle.
Once all requests are completed, we need to use curl_multi_close() to free up memory and close the multiple handles.
The purpose of curl_multi_close is to free all resources associated with multiple handles, but a memory leak can occur if all cURL handles are not removed correctly when calling this function, or if they are not closed completely. This is because PHP's garbage collection mechanism does not clean up the memory occupied by these handles immediately, especially when there are unclosed connections.
To avoid memory leaks, we need to make sure that each cURL handle is removed correctly and that when curl_multi_close is called, make sure that all resources have been released. Here is an example of using curl_multi_close correctly:
// initializationcURLMultiple handles
$multiCurl = curl_multi_init();
// Create multiplecURLHandle
$curlHandles = [];
for ($i = 0; $i < 5; $i++) {
$curlHandles[$i] = curl_init("https://gitbox.net/api/data?id=" . $i);
curl_setopt($curlHandles[$i], CURLOPT_RETURNTRANSFER, true);
curl_multi_add_handle($multiCurl, $curlHandles[$i]);
}
// Perform all requests
$running = null;
do {
curl_multi_exec($multiCurl, $running);
} while ($running > 0);
// Get the content of each request
foreach ($curlHandles as $ch) {
$response = curl_multi_getcontent($ch);
// Here you can process response data
echo $response . "\n";
}
// 移除Handle并关闭每个cURLresource
foreach ($curlHandles as $ch) {
curl_multi_remove_handle($multiCurl, $ch);
curl_close($ch);
}
// 最后关闭Multiple handles
curl_multi_close($multiCurl);
In this example:
We first initialize a cURL multi-handle $multiCurl .
Then create multiple cURL handles and add them to the multiple handles.
After all requests are completed, we get the response of each request through curl_multi_getcontent() .
Use curl_multi_remove_handle() to remove each individual cURL handle from multiple handles and close those handles with curl_close() .
Finally, we call curl_multi_close() to close the multiple handles and free the resource.
Memory management is an important issue in concurrent requests. Here are some optimization suggestions that can help avoid memory leaks:
Close the handle in time : After the request is completed, immediately call curl_multi_remove_handle() and curl_close() to ensure that each handle is closed in time.
Make sure that multiple handles are closed : do not miss closing separate cURL handles before curl_multi_close() . If left out, they will not be released, which may cause memory leaks.
Use curl_multi_select() : When there are many requests, you can use curl_multi_select() to reduce CPU usage and improve efficiency.
Regularly release memory : If the number of requests is very large, you can consider processing the request in batches to avoid processing too many requests at once, causing memory pressure.
curl_multi_close is a powerful tool for closing multiple cURL requests, but it is crucial to use it correctly to avoid memory leaks. By closing each cURL handle in time and ensuring that multiple handles are completely closed, we can effectively manage memory and avoid unnecessary waste of resources. Hopefully, the examples and optimization suggestions in this article can help you better use curl_multi_close to improve the performance and reliability of your code.
