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When using libcurl for multi-threaded HTTP requests, the curl_share_init() function is commonly used to create a shared handle (CURLSH *) so that multiple CURL easy handles can share resources like cookies, DNS, etc. Although libcurl is highly reliable, improper use of curl_share_init() and its associated APIs can still lead to resource leaks or performance issues. Therefore, it is crucial to use dynamic analysis tools such as Valgrind for detection and optimization.
Valgrind is a powerful tool for memory debugging, memory leak detection, and performance analysis, suitable for C/C++ programs in Linux environments. Running PHP extensions or libcurl logic via FFI with Valgrind can help developers discover potential issues.
Here is a simplified PHP example using the multi-threaded shared handle approach in curl:
$sh = curl_share_init();
curl_share_setopt($sh, CURLSHOPT_SHARE, CURL_LOCK_DATA_COOKIE);
curl_share_setopt($sh, CURLSHOPT_SHARE, CURL_LOCK_DATA_DNS);
<p>$ch1 = curl_init();<br>
curl_setopt($ch1, CURLOPT_URL, "<a rel="noopener" target="_new" class="" href="https://m66.net/api/data1">https://m66.net/api/data1</a>");<br>
curl_setopt($ch1, CURLOPT_SHARE, $sh);</p>
<p>$ch2 = curl_init();<br>
curl_setopt($ch2, CURLOPT_URL, "<a rel="noopener" target="_new" class="" href="https://m66.net/api/data2">https://m66.net/api/data2</a>");<br>
curl_setopt($ch2, CURLOPT_SHARE, $sh);</p>
<p>curl_exec($ch1);<br>
curl_exec($ch2);</p>
<p>curl_close($ch1);<br>
curl_close($ch2);</p>
<p>// Ignoring this line will result in the shared handle resource not being released, causing memory leaks<br>
curl_share_close($sh);<br>
Build PHP or C wrapper: Since Valgrind cannot be used directly on PHP scripts, we can encapsulate the above logic as a C extension or integrate libcurl calls into PHP using FFI.
Execute command:
valgrind --leak-check=full --track-origins=yes php your_script.php
Output analysis:
Valgrind will show the following message:
==12345== 48 bytes in 1 blocks are definitely lost in loss record 1 of 10
==12345== at 0x4C2FB55: calloc (vg_replace_malloc.c:711)
==12345== by 0x5B05A3: curl_share_init (share.c:144)
==12345== by 0x10927B: zif_curl_share_init (php_curl.c:2100)
...
The above output indicates that memory allocated after calling curl_share_init() was not properly released using curl_share_close().
In addition to memory leaks, Valgrind can also be used with the callgrind tool to analyze function call frequency and execution time:
valgrind --tool=callgrind php your_script.php
You can then use kcachegrind for graphical analysis to pinpoint which libcurl functions are being called frequently and which shared resources are causing lock contention, guiding you to optimize your sharing strategy—for example, whether to separate DNS sharing or whether to use a more lightweight cookie management approach.
Always call curl_share_close() after using the shared handle;
Avoid unnecessary data sharing, especially in high-concurrency environments, as sharing DNS or cookies may become a bottleneck;
Manage the lifecycle of shared handles uniformly, especially in long-lived PHP scripts;
Perform a memory check with Valgrind before deployment, especially when involving C extensions or FFI calls.
With precise detection from Valgrind, we can ensure that using curl_share_init() does not introduce hidden memory leaks or performance bottlenecks. For developers needing to handle concurrent HTTP requests efficiently in PHP, mastering this toolchain is essential. Using Valgrind along with proper resource management practices can greatly enhance system stability and maintainability.
