Dynamically change database connection Yii

Question

I'm working on a project where multiple websites will be run from one Yii installation. Each website will have his own database though, so the database connection must be dynamically.

What i did, i created a BeginRequestBehavior which will be launched 'onBeginRequest'. Here i will check which url has been called and determine the matching database (not in my code yet) and create (or overwrite) the 'db' component.

<?php
class BeginRequestBehavior extends CBehavior
{

    /**
     * Attaches the behavior object to the component.
     * @param CComponent the component that this behavior is to be attached to
     * @return void
     */

    public function attach($owner)
    {

        $owner->attachEventHandler('onBeginRequest', array($this, 'switchDatabase'));

    }

    /**
     * Change database based on current url, each website has his own database.
     * Config component 'db' is overwritten with this value
     * @param $event event that is called
     * @return void
     */

    public function switchDatabase($event)
    {
        // Here some logic to check which url has been called..

        $db = Yii::createComponent(array(
            'class' => 'CDbConnection',
            'connectionString' => 'mysql:host=localhost;dbname=test',
            'emulatePrepare' => true,
            'username' => 'secret',
            'password' => 'verysecret',
            'charset' => 'utf8',
            'enableProfiling' => true,
            'enableParamLogging' => true
        ));

        Yii::app()->setComponent('db', $db);

    }
}

It's working fine, but is this the correct approach? In other approaches i see people creating their own 'MyActiveRecord' (extending CActiveRecord) for their models and putting the db component in a property. Why do they do it? I'm afraid the database connection will be made too many times than necessary this way.

Answer 1

A much cooler way to use multiple db connection when using yii:

In other words, you need 1 main db to store user profile and a db connection;

For the other slave dbs, you need a single setting; You will switch the db connection when needed. I switch it in my eg using the user id.

I have generated using gii the model for a slave db table, and i think that all your slave db have the same table structure, and on top of that model, i use another class, as shown here;

    'db' => array(
        'class' => 'PortalDbConnection',
        'connectionString' => 'mysql:host=localhost;dbname=mydb',
        'username' => 'dev',
        'password' => '123456',
        'tablePrefix' => '',
        'emulatePrepare' => true,
        'enableParamLogging' => true,
        'enableProfiling' => true,
        'charset' => 'utf8',
    ),
    'dbx' => array(
        'connectionString' => 'mysql:host=localhost;dbname=mydb1',
        'username' => 'dev',
        'password' => '123456',
        'charset' => 'utf8',
        'tablePrefix' => '',
        'autoConnect' => false,
        'class' => 'CDbConnection', //this may be the reason you get errors! always set this
    ),

and now, the php code for your model:

<?php

class DomainSlaveM extends Domain {

    public static function model($className = __CLASS__) {
        return parent::model($className);
    }

    public static $server_id = 1;
    public static $slave_db;

public function getDbConnection() {
    self::$slave_db = Yii::app()->dbx;
    if (self::$slave_db instanceof CDbConnection) {
        self::$slave_db->active = false;
        $config = require(Yii::app()->getBasePath() . '/config/location/flavius.php');
        $connectionString = $config['components']['dbx']['connectionString'];
        self::$slave_db->connectionString = sprintf($connectionString, self::$server_id);
        self::$slave_db->setActive(true);
        return self::$slave_db;
    }
    else
        throw new CDbException(Yii::t('yii', 'Active Record requires a "db" CDbConnection application component.'));
}

    }

and use it like this:

    public function createDomainSlaveM($model) {
//switch the db connection; $server_id gets values, from 1 to N
            DomainSlaveM::$server_id = $model->user_id;
            $model_domain_slave_m = new DomainSlaveM();
            $model_domain_slave_m->attributes = $model->attributes;
            if ($model_domain_slave_m->validate() && $model_domain_slave_m->save()) {
                //ok
            } else {
                //bad
            }
        }

Answer 2

I use a model function for define her DB connection:

public static $conection; // Model attribute

public function getDbConnection(){

    if(self::$conection!==null)
        return self::$conection;

    else{
        self::$conection = Yii::app()->db2; // main.php - DB config name

        if(self::$conection instanceof CDbConnection){
            self::$conection->setActive(true);
            return self::$conection;
        }
        else
            throw new CDbException(Yii::t('yii',"Active Record requires a '$conection' CDbConnection application component."));
    }
}

main.php :

 'db'=>array( 
    'connectionString' => 'mysql:host=192.168.1.*;dbname=database1',
    'emulatePrepare' => true,
    'username' => 'root',
    'password' => 'password',
    'charset' => 'utf8',
    'enableProfiling'=>true,
    'enableParamLogging' => true,
),
'db2'=>array(
    'class'=>'CDbConnection',
    'connectionString' => 'mysql:host=192.168.1.*;dbname=database2',
    'emulatePrepare' => true,
    'username' => 'root',
    'password' => 'password',
    'charset' => 'utf8',
),