feat: instrument wordpress plugins' callbacks on demand (#799)

Improve agent's performance by adding two new toggles around WordPress
instrumentation:
- `newrelic.framework.wordpress.plugins` - indicates if WordPress hooks
callback functions, implemented in WordPress core, plugins and themes,
are to be instrumented.
- `newrelic.framework.wordpress.hooks_threshold` - sets the WordPress
hook's execution duration threshold above which the hook execution will
be captured; used when WordPress hooks callback functions are not
instrumented.

By default, WordPress hooks callback functions are not instrumented and
`newrelic.framework.wordpress.hooks_threshold` is set at 1ms. This
allows to identify which hooks take up most time during request
processing. If more details are needed, i.e. which plugins are the
slowest, `newrelic.framework.wordpress.plugins` need to be set to
`true`.

agent/fw_wordpress.c

@@ -215,6 +215,21 @@ static void free_wordpress_metadata(void* metadata) {
   nr_free(metadata);
 }
 
+static inline void nr_wordpress_hooks_create_metric(nr_segment_t* segment,
+                                       const char* hook_name) {
+  if (NULL == segment) {
+    return;
+  }
+  // need to capture 'now' because segment has not finished yet and therefore
+  // can't use segment->stop_time
+  nrtime_t now = nr_txn_now_rel(segment->txn);
+  nrtime_t duration = nr_time_duration(segment->start_time, now);
+  if (duration >= NRINI(wordpress_hooks_threshold)) {
+    // only create metrics for hooks above threshold
+    nr_wordpress_create_metric(segment, NR_WORDPRESS_HOOK_PREFIX, hook_name);
+  }
+}
+
 static char* nr_wordpress_plugin_from_function(zend_function* func TSRMLS_DC) {
   const char* filename = NULL;
   size_t filename_len;
@@ -452,6 +467,9 @@ NR_PHP_WRAPPER(nr_wordpress_exec_handle_tag) {
 
       NRPRG(wordpress_tag) = nr_wordpress_clean_tag(tag);
       NR_PHP_WRAPPER_CALL;
+      if (0 == NRINI(wordpress_plugins)) {
+        nr_wordpress_hooks_create_metric(auto_segment, NRPRG(wordpress_tag));
+      }
       NRPRG(wordpress_tag) = old_tag;
       if (NULL == NRPRG(wordpress_tag)) {
         NRPRG(check_cufa) = false;
@@ -541,6 +559,9 @@ NR_PHP_WRAPPER(nr_wordpress_apply_filters) {
       NRPRG(wordpress_tag) = nr_wordpress_clean_tag(tag);
 
       NR_PHP_WRAPPER_CALL;
+      if (0 == NRINI(wordpress_plugins)) {
+        nr_wordpress_hooks_create_metric(auto_segment, NRPRG(wordpress_tag));
+      }
       NRPRG(wordpress_tag) = old_tag;
       if (NULL == NRPRG(wordpress_tag)) {
         NRPRG(check_cufa) = false;
@@ -644,14 +665,15 @@ void nr_wordpress_enable(TSRMLS_D) {
 
     nr_php_wrap_user_function(NR_PSTR("do_action_ref_array"),
                               nr_wordpress_exec_handle_tag TSRMLS_CC);
-
+    if (0 != NRINI(wordpress_plugins)) {
 #if ZEND_MODULE_API_NO < ZEND_7_4_X_API_NO
-    nr_php_add_call_user_func_array_pre_callback(
-        nr_wordpress_call_user_func_array TSRMLS_CC);
+      nr_php_add_call_user_func_array_pre_callback(
+          nr_wordpress_call_user_func_array TSRMLS_CC);
 #else
-    nr_php_wrap_user_function(NR_PSTR("add_filter"),
-                                nr_wordpress_add_filter);
+      nr_php_wrap_user_function(NR_PSTR("add_filter"),
+                                  nr_wordpress_add_filter);
 #endif
+    }
   }
 }
 

agent/php_newrelic.h

@@ -268,6 +268,8 @@ nrinistr_t browser_monitoring_loader; /* newrelic.browser_monitoring.loader */
 
 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 */
 nrinistr_t
     wordpress_hooks_skip_filename; /* newrelic.framework.wordpress.hooks_skip_filename
                                     */

agent/php_nrini.c

@@ -2206,6 +2206,22 @@ STD_PHP_INI_ENTRY_EX("newrelic.framework.wordpress.hooks",
                      zend_newrelic_globals,
                      newrelic_globals,
                      nr_on_off_dh)
+STD_PHP_INI_ENTRY_EX("newrelic.framework.wordpress.hooks_threshold",
+                     "1ms",
+                     NR_PHP_REQUEST,
+                     nr_time_mh,
+                     wordpress_hooks_threshold,
+                     zend_newrelic_globals,
+                     newrelic_globals,
+                     0)
+STD_PHP_INI_ENTRY_EX("newrelic.framework.wordpress.plugins",
+                     "0",
+                     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.hooks_skip_filename",
                      "",
                      NR_PHP_REQUEST,

agent/scripts/newrelic.ini.template

@@ -1166,6 +1166,23 @@ newrelic.daemon.logfile = "/var/log/newrelic/newrelic-daemon.log"
 ;
 ;newrelic.framework.wordpress.hooks = true
 
+; Setting: newrelic.framework.wordpress.hooks_threshold
+; Type   : time specification string ("500ms", "1s750ms" etc)
+; Scope  : per-directory
+; Default: 1ms
+; Info   : Sets the threshold above which the New Relic agent will record a
+;          wordpress hooks.
+;
+;newrelic.framework.wordpress.hooks_threshold = 1ms
+
+; Setting: newrelic.framework.wordpress.plugins
+; Type   : boolean
+; Scope  : per-directory
+; Default: false
+; Info   : Indicates if WordPress plugins are to be instrumented.
+;
+;newrelic.framework.wordpress.plugins = false
+
 ; Setting: newrelic.application_logging.enabled
 ; Type   : boolean
 ; Scope  : per-directory

tests/integration/frameworks/wordpress/test_wordpress_apply_filters.php

@@ -13,6 +13,7 @@
 
 /*INI
 newrelic.framework = wordpress
+newrelic.framework.wordpress.hooks_threshold = 0
 */
 
 /*EXPECT

tests/integration/frameworks/wordpress/test_wordpress_do_action.php

@@ -13,6 +13,7 @@
 
 /*INI
 newrelic.framework = wordpress
+newrelic.framework.wordpress.hooks_threshold = 0
 */
 
 /*EXPECT

tests/integration/frameworks/wordpress/test_wordpress_transaction_name_hooks_on.php

@@ -16,6 +16,7 @@
 /*INI
 newrelic.framework = wordpress
 newrelic.framework.wordpress.hooks = true
+newrelic.framework.wordpress.hooks_threshold = 0
 */
 
 /*ENVIRONMENT