Fix fiber support not loaded in open-telemetry/context (#829)

* Add missing autoload entry
* Fix fiber tests
* Trigger error if fiber support cannot be loaded

Author: Nevay

ZendObserverFiber.php

@@ -1,8 +1,6 @@
 <?php
 
-/** @noinspection PhpUndefinedClassInspection */
-/** @noinspection PhpUndefinedNamespaceInspection */
-/** @phan-file-suppress PhanUndeclaredClassReference */
+/** @noinspection PhpUndefinedMethodInspection */
 /** @phan-file-suppress PhanUndeclaredClassCatch */
 /** @phan-file-suppress PhanUndeclaredClassMethod */
 /** @phan-file-suppress PhanUndeclaredMethod */
@@ -11,43 +9,58 @@
 
 namespace OpenTelemetry\Context;
 
+use function extension_loaded;
 use FFI;
-use FFI\Exception;
+use const FILTER_VALIDATE_BOOLEAN;
+use function filter_var;
+use function is_string;
+use const PHP_VERSION_ID;
+use function sprintf;
+use function trigger_error;
 
-class ZendObserverFiber
+/**
+ * @internal
+ */
+final class ZendObserverFiber
 {
-    protected static $fibers = null;
-
-    public function isEnabled(): bool
+    public static function isEnabled(): bool
     {
-        return (
-            PHP_VERSION_ID >= 80100 &&
-            (in_array(getenv('OTEL_PHP_FIBERS_ENABLED'), ['true', 'on', '1'])) &&
-            class_exists(FFI::class)
-        );
+        $enabled = $_SERVER['OTEL_PHP_FIBERS_ENABLED'] ?? false;
+
+        return is_string($enabled)
+            ? filter_var($enabled, FILTER_VALIDATE_BOOLEAN)
+            : (bool) $enabled;
     }
 
-    /**
-     * @psalm-suppress UndefinedClass
-     */
-    public function init(): bool
+    public static function init(): bool
     {
-        if (null === self::$fibers) {
+        static $fibers;
+        if ($fibers) {
+            return true;
+        }
+
+        if (PHP_VERSION_ID < 80100 || !extension_loaded('ffi')) {
+            trigger_error('Context: Fiber context switching not supported, requires PHP >= 8.1 and the FFI extension');
+
+            return false;
+        }
+
+        try {
+            $fibers = FFI::scope('OTEL_ZEND_OBSERVER_FIBER');
+        } catch (FFI\Exception $e) {
             try {
-                $fibers = FFI::scope('OTEL_ZEND_OBSERVER_FIBER');
-            } catch (Exception $e) {
-                try {
-                    $fibers = FFI::load(__DIR__ . '/fiber/zend_observer_fiber.h');
-                } catch (Exception $e) {
-                    return false;
-                }
+                $fibers = FFI::load(__DIR__ . '/fiber/zend_observer_fiber.h');
+            } catch (FFI\Exception $e) {
+                trigger_error(sprintf('Context: Fiber context switching not supported, %s', $e->getMessage()));
+
+                return false;
             }
-            $fibers->zend_observer_fiber_init_register(fn (int $initializing) => Context::storage()->fork($initializing)); //@phpstan-ignore-line
-            $fibers->zend_observer_fiber_switch_register(fn (int $from, int $to) => Context::storage()->switch($to)); //@phpstan-ignore-line
-            $fibers->zend_observer_fiber_destroy_register(fn (int $destroying) => Context::storage()->destroy($destroying)); //@phpstan-ignore-line
-            self::$fibers = $fibers;
         }
 
+        $fibers->zend_observer_fiber_init_register(static fn (int $initializing) => Context::storage()->fork($initializing)); //@phpstan-ignore-line
+        $fibers->zend_observer_fiber_switch_register(static fn (int $from, int $to) => Context::storage()->switch($to)); //@phpstan-ignore-line
+        $fibers->zend_observer_fiber_destroy_register(static fn (int $destroying) => Context::storage()->destroy($destroying)); //@phpstan-ignore-line
+
         return true;
     }
 }

composer.json

@@ -19,7 +19,10 @@
     "autoload": {
         "psr-4": {
             "OpenTelemetry\\Context\\": "."
-        }
+        },
+        "files": [
+            "fiber/initialize_fiber_handler.php"
+        ]
     },
     "suggest": {
         "ext-ffi": "To allow context switching in Fibers"

fiber/initialize_fiber_handler.php

@@ -13,9 +13,7 @@
     return;
 }
 
-$observer = new ZendObserverFiber();
-
-if ($observer->isEnabled() && $observer->init()) {
+if (ZendObserverFiber::isEnabled() && ZendObserverFiber::init()) {
     // ffi fiber support enabled
 } else {
     Context::setStorage(new FiberBoundContextStorage(Context::storage()));