MDL-45724 cache: admin screen now shows store warnings

Implemented a means by which cache store instance can communicate
warnings due to things such as conflicting configurations etc.

cache/admin.php

@@ -52,7 +52,7 @@ $locks = cache_administration_helper::get_lock_summaries();
 
 $title = new lang_string('cacheadmin', 'cache');
 $mform = null;
-$notification = null;
+$notifications = array();
 $notifysuccess = true;
 
 if (!empty($action) && confirm_sesskey()) {
@@ -110,10 +110,10 @@ if (!empty($action) && confirm_sesskey()) {
 
             if (!array_key_exists($store, $stores)) {
                 $notifysuccess = false;
-                $notification = get_string('invalidstore', 'cache');
+                $notifications[] = array(get_string('invalidstore', 'cache'), false);
             } else if ($stores[$store]['mappings'] > 0) {
                 $notifysuccess = false;
-                $notification = get_string('deletestorehasmappings', 'cache');
+                $notifications[] = array(get_string('deletestorehasmappings', 'cache'), false);
             }
 
             if ($notifysuccess) {
@@ -250,10 +250,10 @@ if (!empty($action) && confirm_sesskey()) {
             $confirm = optional_param('confirm', false, PARAM_BOOL);
             if (!array_key_exists($lock, $locks)) {
                 $notifysuccess = false;
-                $notification = get_string('invalidlock', 'cache');
+                $notifications[] = array(get_string('invalidlock', 'cache'), false);
             } else if ($locks[$lock]['uses'] > 0) {
                 $notifysuccess = false;
-                $notification = get_string('deletelockhasuses', 'cache');
+                $notifications[] = array(get_string('deletelockhasuses', 'cache'), false);
             }
             if ($notifysuccess) {
                 if (!$confirm) {
@@ -280,6 +280,16 @@ if (!empty($action) && confirm_sesskey()) {
     }
 }
 
+// Stores can add notices to the cache configuration screen for things like conflicting configurations etc.
+// Here we check each cache to see if it has warnings.
+foreach ($stores as $store) {
+    if (!empty($store['warnings']) && is_array($store['warnings'])) {
+        foreach ($store['warnings'] as $warning) {
+            $notifications[] = array($warning, false);
+        }
+    }
+}
+
 $PAGE->set_title($title);
 $PAGE->set_heading($SITE->fullname);
 /* @var core_cache_renderer $renderer */
@@ -287,10 +297,7 @@ $renderer = $PAGE->get_renderer('core_cache');
 
 echo $renderer->header();
 echo $renderer->heading($title);
-
-if (!is_null($notification)) {
-    echo $renderer->notification($notification, ($notifysuccess)?'notifysuccess' : 'notifyproblem');
-}
+echo $renderer->notififications($notifications);
 
 if ($mform instanceof moodleform) {
     $mform->display();

cache/classes/store.php

@@ -338,4 +338,16 @@ abstract class cache_store implements cache_store_interface {
         // Any stores that have an issue with this will need to override the create_clone method.
         return clone($this);
     }
+
+    /**
+     * Can be overridden to return any warnings this store instance should make to the admin.
+     *
+     * This should be used to notify things like configuration conflicts etc.
+     * The warnings returned here will be displayed on the cache configuration screen.
+     *
+     * @return string[] Returns an array of warnings (strings)
+     */
+    public function get_warnings() {
+        return array();
+    }
 }

cache/locallib.php

@@ -709,7 +709,8 @@ abstract class cache_administration_helper extends cache_helper {
                     'nativelocking' => ($store instanceof cache_is_lockable),
                     'keyawareness' => ($store instanceof cache_is_key_aware),
                     'searchable' => ($store instanceof cache_is_searchable)
-                )
+                ),
+                'warnings' => $store->get_warnings()
             );
             if (empty($details['default'])) {
                 $return[$name] = $record;

cache/renderer.php

@@ -372,4 +372,24 @@ class core_cache_renderer extends plugin_renderer_base {
         $html .= html_writer::end_tag('div');
         return $html;
     }
+
+    /**
+     * Renders an array of notifications for the cache configuration screen.
+     *
+     * @param array $notifications
+     * @return string
+     */
+    public function notififications(array $notifications = array()) {
+        if (count($notifications) === 0) {
+            // There are no notifications to render.
+            return '';
+        }
+        $html = html_writer::start_div('notifications');
+        foreach ($notifications as $notification) {
+            list($message, $notifysuccess) = $notification;
+            $html .= $this->notification($message, ($notifysuccess) ? 'notifysuccess' : 'notifyproblem');
+        }
+        $html .= html_writer::end_div();
+        return $html;
+    }
 }

cache/stores/memcache/lang/en/cachestore_memcache.php

@@ -43,6 +43,7 @@ server.url.com
 ipaddress:port
 servername:port:weight
 </pre>';
+$string['sessionhandlerconflict'] = 'Warning: A memcache instance ({$a}) has being configured to use the same memcached server as sessions. Purging all caches will lead to sessions also being purged.';
 $string['testservers'] = 'Test servers';
 $string['testservers_desc'] = 'The test servers get used for unit tests and for performance tests. It is entirely optional to set up test servers. Servers should be defined one per line and consist of a server address and optionally a port and weight.
 If no port is provided then the default port (11211) is used.';

cache/stores/memcache/lib.php

@@ -437,4 +437,28 @@ class cachestore_memcache extends cache_store implements cache_is_configurable {
     public function my_name() {
         return $this->name;
     }
+
+    /**
+     * Used to notify of configuration conflicts.
+     *
+     * The warnings returned here will be displayed on the cache configuration screen.
+     *
+     * @return string[] Returns an array of warnings (strings)
+     */
+    public function get_warnings() {
+        global $CFG;
+        $warnings = array();
+        if (isset($CFG->session_memcached_save_path) && count($this->servers)) {
+            $bits = explode(':', $CFG->session_memcached_save_path, 3);
+            $host = array_shift($bits);
+            $port = (count($bits)) ? array_shift($bits) : '11211';
+            foreach ($this->servers as $server) {
+                if ($server[0] === $host && $server[1] === $port) {
+                    $warnings[] = get_string('sessionhandlerconflict', 'cachestore_memcache', $this->my_name());
+                    break;
+                }
+            }
+        }
+        return $warnings;
+    }
 }

cache/stores/memcached/lang/en/cachestore_memcached.php

@@ -57,6 +57,7 @@ server.url.com
 ipaddress:port
 servername:port:weight
 </pre>';
+$string['sessionhandlerconflict'] = 'Warning: A memcached instance ({$a}) has being configured to use the same memcached server as sessions. Purging all caches will lead to sessions also being purged.';
 $string['testservers'] = 'Test servers';
 $string['testservers_desc'] = 'The test servers get used for unit tests and for performance tests. It is entirely optional to set up test servers. Servers should be defined one per line and consist of a server address and optionally a port and weight.
 If no port is provided then the default port (11211) is used.';

cache/stores/memcached/lib.php

@@ -494,4 +494,29 @@ class cachestore_memcached extends cache_store implements cache_is_configurable
     public function my_name() {
         return $this->name;
     }
+
+    /**
+     * Used to notify of configuration conflicts.
+     *
+     * The warnings returned here will be displayed on the cache configuration screen.
+     *
+     * @return string[] Returns an array of warnings (strings)
+     */
+    public function get_warnings() {
+        global $CFG;
+        $warnings = array();
+        if (isset($CFG->session_memcached_save_path) && count($this->servers)) {
+            $bits = explode(':', $CFG->session_memcached_save_path, 3);
+            $host = array_shift($bits);
+            $port = (count($bits)) ? array_shift($bits) : '11211';
+
+            foreach ($this->servers as $server) {
+                if ((string)$server[0] === $host && (string)$server[1] === $port) {
+                    $warnings[] = get_string('sessionhandlerconflict', 'cachestore_memcached', $this->my_name());
+                    break;
+                }
+            }
+        }
+        return $warnings;
+    }
 }