Error 500 when returning a cached result

[adrianbenavides]

After an endpoint is correctly cached, subsequent calls may fail with an error 500.

Here is the php log:

php_1        | [29-Apr-2018 16:52:16] WARNING: [pool www] child 78 said into stderr: "NOTICE: PHP message: PHP Fatal error:  Uncaught Exception: Serialization of 'Closure' is not allowed in /var/www/html/web/wp/wp-includes/functions.php:440"
php_1        | [29-Apr-2018 16:32:19] WARNING: [pool www] child 87 said into stderr: "Stack trace:"
php_1        | [29-Apr-2018 16:32:19] WARNING: [pool www] child 87 said into stderr: "#0 /var/www/html/web/app/object-cache.php(1130): serialize(Object(WP_REST_Response))"
php_1        | [29-Apr-2018 16:32:19] WARNING: [pool www] child 87 said into stderr: "#1 /var/www/html/web/app/object-cache.php(836): WP_Object_Cache->maybe_serialize(Object(WP_REST_Response))"
php_1        | [29-Apr-2018 16:32:19] WARNING: [pool www] child 87 said into stderr: "#2 /var/www/html/web/app/object-cache.php(227): WP_Object_Cache->set('/wp-json/wp-api...', Object(WP_REST_Response), 'rest_api', 600)"
php_1        | [29-Apr-2018 16:32:19] WARNING: [pool www] child 87 said into stderr: "#3 /var/www/html/web/app/plugins/wp-rest-api-object-cache/src/RestApi/RestDispatch.php(225): wp_cache_set('/wp-json/wp-api...', Object(WP_REST_Response), 'rest_api', 600)"
php_1        | [29-Apr-2018 16:32:19] WARNING: [pool www] child 87 said into stderr: "#4 /var/www/html/web/app/plugins/wp-rest-api-object-cache/src/RestApi/RestDispatch.php(146): Dwnload\WpRestApi\RestApi\RestDispatch->getCachedResult(Object(WP_REST_Server), Object(WP_REST_Request), '/wp-json/wp-api...', 'rest_api')"
php_1        | [29-Apr-2018 16:32:19] WARNING: [pool www] child 87 said into stderr: "#5 /var/www/html/vendor/thefrosty/wp-utilities/src/Plugin/HooksTrait.php(145): Dwnload\WpRestApi\RestApi\RestDispatch->preDispatch..."
php_1        | 172.18.0.8 -  29/Apr/2018:16:32:18 +0000 "GET /index.php" 500

Also, there is a warning message:

php_1        | [29-Apr-2018 16:27:21] WARNING: [pool www] child 87 said into stderr: "NOTICE: PHP message: PHP Warning:  call_user_func_array() expects parameter 1 to be a valid callback, cannot access protected method Dwnload\WpRestApi\WpAdmin\Admin::renderPage() in /var/www/html/web/wp/wp-includes/class-wp-hook.php on line 286"
php_1        | [29-Apr-2018 16:27:21] WARNING: [pool www] child 87 said into stderr: "NOTICE: PHP message: PHP Stack trace:"
php_1        | [29-Apr-2018 16:27:21] WARNING: [pool www] child 87 said into stderr: "NOTICE: PHP message: PHP   1. {main}() /var/www/html/web/wp/wp-admin/options-general.php:0"
php_1        | [29-Apr-2018 16:27:21] WARNING: [pool www] child 87 said into stderr: "NOTICE: PHP message: PHP   2. require_once() /var/www/html/web/wp/wp-admin/options-general.php:10"
php_1        | [29-Apr-2018 16:27:21] WARNING: [pool www] child 87 said into stderr: "NOTICE: PHP message: PHP   3. do_action($tag = *uninitialized*, $arg = *uninitialized*) /var/www/html/web/wp/wp-admin/admin.php:224"
php_1        | [29-Apr-2018 16:27:21] WARNING: [pool www] child 87 said into stderr: "NOTICE: PHP message: PHP   4. WP_Hook->do_action($args = *uninitialized*) /var/www/html/web/wp/wp-includes/plugin.php:453"
php_1        | [29-Apr-2018 16:27:21] WARNING: [pool www] child 87 said into stderr: "NOTICE: PHP message: PHP   5. WP_Hook->apply_filters($value = *uninitialized*, $args = *uninitialized*) ****

Using

• wp-rest-api-object-cache: 1.2.0
• WordPress Version: 4.9.5
• PHP Version: 7.2.5
• MySQL Version: 5.5.5
• Server Software: nginx/1.13.12

[adrianbenavides]

I've found what was causing the error 500: I forgot to uninstall the Redis Object plugin before testing this one.

The warning message is still there though and I can't see the content of the plugins' admin page.