Make nginx readiness endpoint dependant on a working socket to fpm

deploy/config/local/nginx/server.conf

@@ -116,6 +116,11 @@ server {
         set $skip_cache 1;
     }
 
+    # ...it's to the readiness endpoint
+    if ($request_uri = "/readiness") {
+        set $skip_cache 1;
+    }
+
     # ...it's from a logged in user, the cookie 'wordpress_no_cache' exists.
     if ($http_cookie ~* "comment_author|wordpress_[a-f0-9]+|wp-postpass|wordpress_no_cache|wordpress_logged_in") {
         set $skip_cache 1;
@@ -303,8 +308,18 @@ server {
     # LOCATIONS - heath
     ##
 
-    location ~ ^/(liveness|readiness)$ {
+    location = /liveness {
         return 200;
     }
 
+    location = /readiness {
+        # Make sure we can connect to php-fpm via the socket.
+        set $script_name /metrics/socket.php;
+
+        fastcgi_param SCRIPT_FILENAME $document_root$script_name;
+        include fastcgi_params;
+
+        fastcgi_pass fpm;
+    }
+
 }

deploy/config/server.conf

@@ -135,6 +135,11 @@ server {
         set $skip_cache 1;
     }
 
+    # ...it's to the liveness or readiness endpoint
+    if ($request_uri ~* "^(/liveness|/readiness)$" {
+        set $skip_cache 1;
+    }
+
     # ...it's from a logged in user, the cookie 'wordpress_no_cache' exists.
     if ($http_cookie ~* "comment_author|wordpress_[a-f0-9]+|wp-postpass|wordpress_no_cache|wordpress_logged_in") {
         set $skip_cache 1;
@@ -325,12 +330,26 @@ server {
     # LOCATIONS - health
     ##
 
-    location ~ ^/(liveness|readiness)$ {
+    location = /liveness {
         if ($ip_access_health = 0) {
             return 404;
         }
 
         return 200;
     }
 
+    location = /readiness {
+        if ($ip_access_health = 0) {
+            return 404;
+        }
+
+        # Make sure we can connect to php-fpm via the socket.
+        set $script_name /metrics/socket.php;
+
+        fastcgi_param SCRIPT_FILENAME $document_root$script_name;
+        include fastcgi_params;
+
+        fastcgi_pass fpm;
+    }
+
 }

public/metrics/service.php

@@ -34,7 +34,6 @@ class Metrics
      */
     public function __construct()
     {
-
         // Get the ip group of the incoming request.
         $ip_group = $_SERVER['HTTP_X_MOJ_IP_GROUP'] ?? 0;
 
@@ -49,36 +48,42 @@ public function __construct()
 
         $this->home_url = env('WP_HOME');
 
-        // Define an array of metrics that we want to generate.
+        // Define an array of metrics that we want to generate for all environments.
         $this->metrics_properties = [
-            'http_status_code_control' => [
-                'help' => 'The http status code when accessing an open site.',
-                'type' => 'gauge',
-                'callback' => [$this, 'getStatusCode'],
-                'args' => [$this::OPEN_URL]
-            ],
-            'http_status_code_invalid_header' => [
-                'help' => 'The http status code of when sending X-Moj-Ip-Group header.',
-                'type' => 'gauge',
-                'callback' => [$this, 'getStatusCode'],
-                'args' => [
-                    $this->home_url,
-                    ['headers' => ['X-Moj-Ip-Group' => 0]]
-                ]
-            ],
-            'http_status_code_health' => [
-                'help' => 'The http status code of /health.',
-                'type' => 'gauge',
-                'callback' => [$this, 'getStatusCode'],
-                'args' => ["{$this->home_url}/health"]
-            ],
             'http_status_code_wp_home' => [
                 'help' => 'The http status code when accessing this service via it\'s full url as defined in WP_HOME.',
                 'type' => 'gauge',
                 'callback' => [$this, 'getStatusCode'],
                 'args' => [$this->home_url]
             ]
         ];
+
+        if ('production' !== env('WP_ENV')) {
+            // Add other metrics for non-production.
+            $this->metrics_properties = array_merge($this->metrics_properties, [
+                'http_status_code_control' => [
+                    'help' => 'The http status code when accessing an open site.',
+                    'type' => 'gauge',
+                    'callback' => [$this, 'getStatusCode'],
+                    'args' => [$this::OPEN_URL]
+                ],
+                'http_status_code_invalid_header' => [
+                    'help' => 'The http status code of when sending X-Moj-Ip-Group header.',
+                    'type' => 'gauge',
+                    'callback' => [$this, 'getStatusCode'],
+                    'args' => [
+                        $this->home_url,
+                        ['headers' => ['X-Moj-Ip-Group' => 0]]
+                    ]
+                ],
+                'http_status_code_health' => [
+                    'help' => 'The http status code of /health.',
+                    'type' => 'gauge',
+                    'callback' => [$this, 'getStatusCode'],
+                    'args' => ["{$this->home_url}/health"]
+                ]
+            ]);
+        }
     }
 
     /**
@@ -140,6 +145,7 @@ public function serveMetrics(): void
     {
         header('Content-Type', 'text/plain');
         echo $this->getServiceMetrics();
+        unset($this->guzzle_client);
         exit();
     }
 }

public/metrics/socket.php

@@ -0,0 +1,3 @@
+<?php
+
+echo 'OK';