feat: instrument wordpress core callbacks on demand (#802)

Improve agent's performance by adding a new toggle around WordPress
instrumentation:

* `newrelic.framework.wordpress.core` - indicates if WordPress hooks
callback functions, implemented in WordPress core, are to be
instrumented.

By default WordPress hook callbacks from WordPress core are not
instrumented because it increases agent's overhead. It is however
possible to enable this instrumentation with INI setting.

agent/fw_wordpress.c

@@ -337,10 +337,12 @@ NR_PHP_WRAPPER(nr_wordpress_wrap_hook) {
 #endif
 
   NR_PHP_WRAPPER_CALL;
-
-  nr_wordpress_create_metric(auto_segment, NR_WORDPRESS_HOOK_PREFIX,
-                             NRPRG(wordpress_tag));
-  nr_wordpress_create_metric(auto_segment, NR_WORDPRESS_PLUGIN_PREFIX, plugin);
+  if (NULL != plugin || NRINI(wordpress_core)) {
+    nr_wordpress_create_metric(auto_segment, NR_WORDPRESS_HOOK_PREFIX,
+                               NRPRG(wordpress_tag));
+    nr_wordpress_create_metric(auto_segment, NR_WORDPRESS_PLUGIN_PREFIX,
+                               plugin);
+  }
 }
 NR_PHP_WRAPPER_END
 
@@ -631,20 +633,23 @@ NR_PHP_WRAPPER(nr_wordpress_add_filter) {
   if (true == wrap_hook) {
     nruserfn_t* callback_wraprec;
     zval* callback = nr_php_arg_get(2, NR_EXECUTE_ORIG_ARGS);
-    /* the callback here can be any PHP callable. nr_php_wrap_generic_callable
-   * checks that a valid callable is passed */
-    callback_wraprec = nr_php_wrap_generic_callable(callback, nr_wordpress_wrap_hook);
-
-    // We can cheat here: wraprecs on callables are always transient, so if
-    // there's a wordpress_plugin_theme set we know it's from this transaction,
-    // and we don't have any issues around a possible multi-tenant setup.
-    if (callback_wraprec && NULL == callback_wraprec->wordpress_plugin_theme) {
-      // Unlike Drupal, we don't free the wordpress_plugin_theme, since we know
-      // it's transient anyway, and we only set the field if it was previously
-      // NULL.
-      zend_function* fn = nr_php_zval_to_function(callback);
-      callback_wraprec->wordpress_plugin_theme
-          = nr_wordpress_plugin_from_function(fn);
+    zend_function* zf = nr_php_zval_to_function(callback);
+    if (NULL != zf) {
+      char* wordpress_plugin_theme = nr_wordpress_plugin_from_function(zf);
+      if (NULL != wordpress_plugin_theme || NRINI(wordpress_core)) {
+        callback_wraprec = nr_php_wrap_callable(zf, nr_wordpress_wrap_hook);
+        // We can cheat here: wraprecs on callables are always transient, so if
+        // there's a wordpress_plugin_theme set we know it's from this
+        // transaction, and we don't have any issues around a possible
+        // multi-tenant setup.
+        if (NULL != callback_wraprec
+            && NULL == callback_wraprec->wordpress_plugin_theme) {
+          // Unlike Drupal, we don't free the wordpress_plugin_theme, since we
+          // know it's transient anyway, and we only set the field if it was
+          // previously NULL.
+          callback_wraprec->wordpress_plugin_theme = wordpress_plugin_theme;
+        }
+      }
     }
     nr_php_arg_release(&callback);
   }

agent/php_newrelic.h

@@ -270,6 +270,7 @@ nrinibool_t drupal_modules;  /* newrelic.framework.drupal.modules */
 nrinibool_t wordpress_hooks; /* newrelic.framework.wordpress.hooks */
 nrinitime_t wordpress_hooks_threshold; /* newrelic.framework.wordpress.hooks_threshold */
 nrinibool_t wordpress_plugins; /* newrelic.framework.wordpress.plugins */
+nrinibool_t wordpress_core;  /* newrelic.framework.wordpress.core */
 nrinistr_t
     wordpress_hooks_skip_filename; /* newrelic.framework.wordpress.hooks_skip_filename
                                     */

agent/php_nrini.c

@@ -2215,13 +2215,21 @@ STD_PHP_INI_ENTRY_EX("newrelic.framework.wordpress.hooks_threshold",
                      newrelic_globals,
                      0)
 STD_PHP_INI_ENTRY_EX("newrelic.framework.wordpress.plugins",
-                     "0",
+                     "1",
                      NR_PHP_REQUEST,
                      nr_boolean_mh,
                      wordpress_plugins,
                      zend_newrelic_globals,
                      newrelic_globals,
                      nr_on_off_dh)
+STD_PHP_INI_ENTRY_EX("newrelic.framework.wordpress.core",
+                     "0",
+                     NR_PHP_REQUEST,
+                     nr_boolean_mh,
+                     wordpress_core,
+                     zend_newrelic_globals,
+                     newrelic_globals,
+                     nr_on_off_dh)
 STD_PHP_INI_ENTRY_EX("newrelic.framework.wordpress.hooks_skip_filename",
                      "",
                      NR_PHP_REQUEST,

agent/scripts/newrelic.ini.template

@@ -1178,10 +1178,18 @@ newrelic.daemon.logfile = "/var/log/newrelic/newrelic-daemon.log"
 ; Setting: newrelic.framework.wordpress.plugins
 ; Type   : boolean
 ; Scope  : per-directory
-; Default: false
+; Default: true
 ; Info   : Indicates if WordPress plugins are to be instrumented.
 ;
-;newrelic.framework.wordpress.plugins = false
+;newrelic.framework.wordpress.plugins = true
+
+; Setting: newrelic.framework.wordpress.core
+; Type   : boolean
+; Scope  : per-directory
+; Default: false
+; Info   : Indicates if WordPress core hook callbacks are to be instrumented.
+;
+;newrelic.framework.wordpress.core = false
 
 ; Setting: newrelic.application_logging.enabled
 ; Type   : boolean

tests/integration/frameworks/wordpress/mock-wordpress-app.php

@@ -0,0 +1,38 @@
+<?php
+
+/* A simple mock of a WordPress app */
+
+require_once __DIR__.'/wp-config.php';
+
+// Register core action
+add_action("wp_init", "wp_core_action_1");
+add_action("wp_init", "wp_core_action_2");
+add_action("wp_init", "wp_core_action_3");
+add_action("wp_init", "wp_core_action_4");
+
+/* Emulate loading custom plugin and theme */
+require_once __DIR__.'/wp-content/plugins/mock-plugin1.php';
+require_once __DIR__.'/wp-content/plugins/mock-plugin2.php';
+require_once __DIR__.'/wp-content/themes/mock-theme1.php';
+require_once __DIR__.'/wp-content/themes/mock-theme2.php';
+
+// Register custom plugin action
+add_action("wp_loaded", "plugin1_action_1");
+add_action("wp_loaded", "plugin2_action_1");
+
+// Emulate WordPress initialization:
+do_action("wp_init");
+do_action("wp_loaded");
+
+// Register custom theme filter
+add_filter("the_content", "wp_core_filter_1");
+
+// Register custom theme filter
+add_filter("template_include", "theme1_identity_filter");
+add_filter("template_include", "theme2_identity_filter");
+
+// Emulate WordPress loading a template to render a page:
+$template = apply_filters("template_include", "./path/to/templates/page-template.php");
+
+// Emulate WordPress rendering the content for the page:
+$content = apply_filters("the_content", "Lore ipsum HTML");

tests/integration/frameworks/wordpress/test_wordpress_00.php

@@ -0,0 +1,54 @@
+<?php
+/*
+ * Copyright 2020 New Relic Corporation. All rights reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/*DESCRIPTION
+Test WordPress default instrumentation. The agent should:
+ - detect WordPress framework
+ - name the web transaction as an 'Action' named after the template used to generate the page
+ - detect custom plugins and themes
+ - generate hooks metrics but only when hook executes functions from custom
+   plugin or theme; the agent must not generate hooks metrics when hook executes
+   functions from wordpress core
+No errors should be generated.
+*/
+
+/*SKIPIF
+<?php
+// This test checks if add_filter is instrumented and this function is only
+// instrumented in PHPs 7.4 because it is used to wrap hook callback functions.
+// Older PHPs use call_user_func_array instrumentation to wrap hook callbacks.
+if (version_compare(PHP_VERSION, '7.4', '<')) {
+    die("skip: PHP >= 7.4 required\n");
+}
+*/
+
+/*ENVIRONMENT
+REQUEST_METHOD=GET
+*/
+
+/*EXPECT_METRICS_EXIST
+Supportability/framework/WordPress/detected
+WebTransaction/Action/page-template
+Supportability/InstrumentedFunction/apply_filters
+Supportability/InstrumentedFunction/do_action
+Supportability/InstrumentedFunction/add_filter
+Framework/WordPress/Hook/wp_loaded
+Framework/WordPress/Hook/template_include
+Framework/WordPress/Plugin/mock-plugin1
+Framework/WordPress/Plugin/mock-plugin2
+Framework/WordPress/Plugin/mock-theme1
+Framework/WordPress/Plugin/mock-theme2
+*/
+
+/*EXPECT_METRICS_DONT_EXIST
+Framework/WordPress/Hook/wp_init
+Framework/WordPress/Hook/the_content
+*/
+
+/*EXPECT_ERROR_EVENTS null */
+
+/* WordPress mock app */
+require_once __DIR__.'/mock-wordpress-app.php';

tests/integration/frameworks/wordpress/test_wordpress_00.php7.php

@@ -0,0 +1,46 @@
+<?php
+/*
+ * Copyright 2020 New Relic Corporation. All rights reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/*DESCRIPTION
+Test WordPress default instrumentation. The agent should:
+ - detect WordPress framework
+ - name the web transaction as an 'Action' named after the template used to generate the page
+ - detect custom plugins and themes
+ - generate hooks metrics but only when hook executes functions from custom
+   plugin or theme; the agent must not generate hooks metrics when hook executes
+   functions from wordpress core
+No errors should be generated.
+*/
+
+/*SKIPIF
+*/
+
+/*ENVIRONMENT
+REQUEST_METHOD=GET
+*/
+
+/*EXPECT_METRICS_EXIST
+Supportability/framework/WordPress/detected
+WebTransaction/Action/page-template
+Supportability/InstrumentedFunction/apply_filters
+Supportability/InstrumentedFunction/do_action
+Framework/WordPress/Hook/wp_loaded
+Framework/WordPress/Hook/template_include
+Framework/WordPress/Plugin/mock-plugin1
+Framework/WordPress/Plugin/mock-plugin2
+Framework/WordPress/Plugin/mock-theme1
+Framework/WordPress/Plugin/mock-theme2
+*/
+
+/*EXPECT_METRICS_DONT_EXIST
+Framework/WordPress/Hook/wp_init
+Framework/WordPress/Hook/the_content
+*/
+
+/*EXPECT_ERROR_EVENTS null */
+
+/* WordPress mock app */
+require_once __DIR__.'/mock-wordpress-app.php';

tests/integration/frameworks/wordpress/test_wordpress_01.php

@@ -0,0 +1,47 @@
+<?php
+/*
+ * Copyright 2020 New Relic Corporation. All rights reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/*DESCRIPTION
+Test WordPress instrumentation when hooks are not instrumented. The agent should:
+ - detect WordPress framework
+ - name the web transaction as an 'Action' named after the template used to generate the page
+The agent should not:
+ - detect custom plugins and themes
+ - generate hooks metrics
+No errors should be generated.
+*/
+
+/*INI
+newrelic.framework.wordpress.hooks = false
+*/
+
+/*ENVIRONMENT
+REQUEST_METHOD=GET
+*/
+
+/*EXPECT_METRICS_EXIST
+Supportability/framework/WordPress/detected
+WebTransaction/Action/page-template
+Supportability/InstrumentedFunction/apply_filters
+*/
+
+/*EXPECT_METRICS_DONT_EXIST
+Supportability/InstrumentedFunction/do_action
+Supportability/InstrumentedFunction/add_filter
+Framework/WordPress/Hook/wp_loaded
+Framework/WordPress/Hook/template_include
+Framework/WordPress/Plugin/mock-plugin1
+Framework/WordPress/Plugin/mock-plugin2
+Framework/WordPress/Plugin/mock-theme1
+Framework/WordPress/Plugin/mock-theme2
+Framework/WordPress/Hook/wp_init
+Framework/WordPress/Hook/the_content
+*/
+
+/*EXPECT_ERROR_EVENTS null */
+
+/* WordPress mock app */
+require_once __DIR__.'/mock-wordpress-app.php';

tests/integration/frameworks/wordpress/test_wordpress_02.php

@@ -0,0 +1,53 @@
+<?php
+/*
+ * Copyright 2020 New Relic Corporation. All rights reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/*DESCRIPTION
+Test WordPress instrumentation when hooks are instrumented but custom plugins are not.
+This setting is not very useful unless wordpress core performance is to be observed.
+The agent should:
+ - detect WordPress framework
+ - name the web transaction as an 'Action' named after the template used to generate the page
+ - generate hooks metrics for all callback functions executions that last longer than
+   threshold duration; the execution time of callback functions from wordpress core,
+   custom plugins and themes is captured.
+The agent should not:
+ - detect and report custom plugins and themes
+No errors should be generated.
+*/
+
+/*INI
+newrelic.framework.wordpress.hooks = true
+newrelic.framework.wordpress.plugins = false
+newrelic.framework.wordpress.hooks_threshold = 0
+*/
+
+/*ENVIRONMENT
+REQUEST_METHOD=GET
+*/
+
+/*EXPECT_METRICS_EXIST
+Supportability/framework/WordPress/detected
+WebTransaction/Action/page-template
+Supportability/InstrumentedFunction/apply_filters
+Supportability/InstrumentedFunction/do_action
+Framework/WordPress/Hook/wp_loaded
+Framework/WordPress/Hook/template_include
+Framework/WordPress/Hook/wp_init
+Framework/WordPress/Hook/the_content
+*/
+
+/*EXPECT_METRICS_DONT_EXIST
+Supportability/InstrumentedFunction/add_filter
+Framework/WordPress/Plugin/mock-plugin1
+Framework/WordPress/Plugin/mock-plugin2
+Framework/WordPress/Plugin/mock-theme1
+Framework/WordPress/Plugin/mock-theme2
+*/
+
+/*EXPECT_ERROR_EVENTS null */
+
+/* WordPress mock app */
+require_once __DIR__.'/mock-wordpress-app.php';