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;
+    }
+
 }

public/metrics/service.php

@@ -140,6 +140,7 @@ 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';