update:xhprof 支持创建固定大小集合

src/Mongo/MongoBase.php

@@ -99,6 +99,21 @@ abstract class MongoBase
                 );
             }
             $this->database = $this->client->selectDatabase($this->getDatabaseName());
+
+            // xhprof 需要 显示的创建固定大小的集合
+            $db_collection  = [];
+            if ($this->getDatabaseName() === 'xhprof') {
+                foreach ($this->database->listCollections() as $item){
+                    $db_collection[] = $item['name'];
+                }
+
+                if (!in_array($this->getCollectionName(), $db_collection, true)) {
+
+                    //默认创建固定20GB大小的集合
+                    $this->database->createCollection($this->getCollectionName(),['capped' => true,'size' => 21474836480]);
+                }
+            }
+
             $this->collection = $this->database->selectCollection($this->getCollectionName(), $this->getCollectionOptions());
         }
     }