Added warning log for Xdebug incompatibility (#1256)

agent/native/ext/lifecycle.cpp

@@ -414,12 +414,19 @@ void elasticApmRequestInit()
     enableAccessToServerGlobal();
     bool preloadDetected = requestCounter == 1 ? detectOpcachePreload() : false;
 
-    if (config && config->debugDiagnosticsFile && !preloadDetected && requestCounter <= 2) {
+    if (!preloadDetected && requestCounter <= 2) {
         if (ELASTICAPM_G(globals)->sharedMemory_->shouldExecuteOneTimeTaskAmongWorkers()) {
-            try {
-                elasticapm::utils::storeDiagnosticInformation(elasticapm::utils::getParameterizedString(config->debugDiagnosticsFile), *(ELASTICAPM_G(globals)->bridge_));
-            } catch (std::exception const &e) {
-                ELASTIC_APM_LOG_WARNING( "Unable to write agent diagnostics: %s", e.what() );
+            using namespace std::string_view_literals;
+            if ( ELASTICAPM_G( globals )->bridge_->isExtensionLoaded( "xdebug"sv ) ) {
+                ELASTIC_APM_LOG_WARNING( "Xdebug is loaded, which is not supported by the Elastic APM Agent. This may lead to stability or memory issues");
+            }
+
+            if (config && config->debugDiagnosticsFile) {
+                try {
+                    elasticapm::utils::storeDiagnosticInformation(elasticapm::utils::getParameterizedString(config->debugDiagnosticsFile), *(ELASTICAPM_G(globals)->bridge_));
+                } catch (std::exception const &e) {
+                    ELASTIC_APM_LOG_WARNING( "Unable to write agent diagnostics: %s", e.what() );
+                }
             }
         }
     }

agent/native/libcommon/code/PhpBridgeInterface.h

@@ -22,7 +22,7 @@ class PhpBridgeInterface {
     virtual std::string getPhpInfo() const = 0;
 
     virtual std::string_view getPhpSapiName() const = 0;
-
+    virtual bool isExtensionLoaded(std::string_view extensionName) const = 0;
 };
 
 }

agent/native/libphpbridge/code/Debugging.cpp

@@ -5,11 +5,15 @@
 #include <main/SAPI.h>
 #include <Zend/zend_modules.h>
 #include <Zend/zend_extensions.h>
+#include <Zend/zend_string.h>
 
 namespace elasticapm::php {
 
 using namespace std::string_view_literals;
 
+bool PhpBridge::isExtensionLoaded(std::string_view extensionName) const {
+    return zend_hash_str_find(&module_registry, extensionName.data(), extensionName.length()) != nullptr;
+}
 static int getModuleData(zval *item, void *arg) {
     zend_module_entry *module = (zend_module_entry *)Z_PTR_P(item);
 
@@ -64,7 +68,7 @@ std::string PhpBridge::getPhpInfo() const {
 
     std::string output;
     phpInfoTempBuffer = &output;
-    
+
     auto orig_php_info_as_text = sapi_module.phpinfo_as_text;
     sapi_module.phpinfo_as_text = 1;
 

agent/native/libphpbridge/code/PhpBridge.h

@@ -17,6 +17,7 @@ class PhpBridge : public PhpBridgeInterface {
     std::string getPhpInfo() const final;
 
     std::string_view getPhpSapiName() const final;
+    bool isExtensionLoaded(std::string_view extensionName) const final;
 
 protected:
     zend_class_entry *findClassEntry(std::string_view className) const;

docs/setup.asciidoc

@@ -120,3 +120,8 @@ the installation directory of the agent (by default `/opt/elastic/apm-agent-php`
 must be located within a path included in the
 https://www.php.net/manual/en/ini.core.php#ini.open-basedir[`open_basedir`] value.
 Otherwise, the agent will not be loaded correctly.
+
+[discrete]
+[[limitation-xdebug]]
+==== `Xdebug` stability and memory issues
+We strongly advise against running the agent alongside the xdebug extension. Using both extensions simultaneously can lead to stability issues in the instrumented application, such as memory leaks. It is highly recommended to disable xdebug, preferably by preventing it from loading in the `php.ini` configuration file.