Added support for readonly connections

Author: samnotsowise

CHANGELOG.md

@@ -1,5 +1,10 @@
 # Change Log
 
+### 1.5.2
+
+* Added:    Read/Write connection splitting support
+* Added:    Read only connection stem settings
+
 ### 1.5.1
 
 * Fixed:    MysqlJsonColumn now supports $decodeAsArrays

src/Repositories/MySql/MySql.php

@@ -107,7 +107,8 @@ protected function fetchMissingObjectData(Model $object, $uniqueIdentifier, $rel
 
         $data = self::returnFirstRow(
             "SELECT * FROM `" . $table . "` WHERE `{$schema->uniqueIdentifierColumnName}` = :id",
-            ["id" => $uniqueIdentifier]
+            ["id" => $uniqueIdentifier],
+            self::getReadOnlyConnection()
         );
 
         if ($data != null) {
@@ -301,12 +302,13 @@ public function createCursorForCollection(RepositoryCollection $collection)
             $sql = preg_replace("/^SELECT /", "SELECT SQL_CALC_FOUND_ROWS ", $sql);
         }
 
-        $statement = static::executeStatement((string)$sql, $params);
+        $connection = self::getReadOnlyConnection();
+        $statement = static::executeStatement((string)$sql, $params, $connection);
 
         $count = $statement->rowCount();
 
         if ($hasLimit){
-            $count = static::returnSingleValue("SELECT FOUND_ROWS()");
+            $count = static::returnSingleValue("SELECT FOUND_ROWS()", [], $connection);
         }
 
         $cursor = new MySqlCursor($statement, $this, $count, $collection->additionalColumns);

src/Repositories/PdoRepository.php

@@ -44,6 +44,8 @@ abstract class PdoRepository extends Repository
      */
     protected static $defaultConnection = null;
 
+    protected static $readOnlyConnection = null;
+
     private static $pdoParamAliasesUsed = [];
 
     /**
@@ -81,11 +83,46 @@ public static function getDefaultConnection()
             $databaseSettings = StemSettings::singleton();
 
             self::$defaultConnection = static::getConnection($databaseSettings);
+
+            if ($databaseSettings->stickyWriteConnection) {
+                self::$readOnlyConnection = self::$defaultConnection;
+            }
         }
 
         return self::$defaultConnection;
     }
 
+    public static function getReadOnlyConnection()
+    {
+        if (self::$readOnlyConnection === null) {
+            $databaseSettings = StemSettings::singleton();
+
+            if (
+                // readonly port/host are different to default
+                $databaseSettings->readOnlyHost !== $databaseSettings->host
+                || $databaseSettings->readOnlyPort !== $databaseSettings->port
+            ) {
+                $readOnlySettings = clone StemSettings::singleton();
+                $readOnlyMap = [
+                    'host' => 'readOnlyHost',
+                    'port' => 'readOnlyPort',
+                    'username' => 'readOnlyUsername',
+                    'password' => 'readOnlyPassword',
+                ];
+                foreach ($readOnlyMap as $primaryProp => $readOnlyProp) {
+                    if ($readOnlySettings->$readOnlyProp) {
+                        $readOnlySettings->$primaryProp = $readOnlySettings->$readOnlyProp;
+                    }
+                }
+                self::$readOnlyConnection = static::getConnection($readOnlySettings);
+            } else {
+                self::$readOnlyConnection = self::getDefaultConnection();
+            }
+        }
+
+        return self::$readOnlyConnection;
+    }
+
     /**
      * @param StemSettings $dbSettings
      * @return \PDO
@@ -104,6 +141,13 @@ public static function resetDefaultConnection()
         self::$defaultConnection = null;
     }
 
+    /**
+     * Discards the default connection.
+     */
+    public static function resetReadOnlyConnection()
+    {
+        self::$readOnlyConnection = null;
+    }
 
     /**
      * A collection of PDO objects for each active connection.
@@ -231,7 +275,11 @@ public static function executeInsertStatement($sql, $namedParameters = [], $conn
      */
     public static function returnSingleValue($statement, $namedParameters = [], $connection = null)
     {
-        $statement = self::executeStatement($statement, $namedParameters, $connection);
+        $statement = self::executeStatement(
+            $statement,
+            $namedParameters,
+            $connection !== null ? $connection : self::getReadOnlyConnection()
+        );
 
         return $statement->fetchColumn(0);
     }
@@ -246,7 +294,11 @@ public static function returnSingleValue($statement, $namedParameters = [], $con
      */
     public static function returnFirstRow($statement, $namedParameters = [], $connection = null)
     {
-        $statement = self::executeStatement($statement, $namedParameters, $connection);
+        $statement = self::executeStatement(
+            $statement,
+            $namedParameters,
+            $connection !== null ? $connection : self::getReadOnlyConnection()
+        );
 
         return $statement->fetch(\PDO::FETCH_ASSOC);
     }

src/StemSettings.php

@@ -32,6 +32,16 @@ class StemSettings extends Settings
     public $password = "";
     public $database = "";
 
+    // allows connections to be split so that reads and writes
+    public $readOnlyHost = "";
+    public $readOnlyPort = "";
+    public $readOnlyUsername = "";
+    public $readOnlyPassword = "";
+
+    // Useful if you intend to read immediately after writing and your read only connection has lag (eg replication).
+    // This will probably make read only connections pointless if writes happen throughout reads (eg db logging).
+    public $stickyWriteConnection = false;
+
     /**
      * @var \DateTimeZone
      */