django數據庫分庫migrate

最近在研究微服務和分佈式，設計到了數據庫分庫，記錄一下
首先，建立多個數據庫，若是是已經生成的數據庫，能夠分庫，這裏我是新建立的項目，恰好能夠用來嘗試
我是用docker建立的mysql數據庫容器
拉取docker鏡像：
docker pull mysql:5.7
建立容器：
docker run --name=mysql5.7 -p 13306:3306 -e MYSQL_ROOT_PASSWORD=123456 -d mysql:5.7
建立多個mysql容器以後，django配置好相應數據庫，我這裏分紅了三個數據庫，一個是默認，放django的user，group，permission，session之類的，另一個是order和sale兩個app的，這裏我打算下一步微服務的時候再拆開，這裏先記錄分庫的事情，數據庫代碼以下：

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.mysql',
        'HOST': '192.168.1.112',
        'PORT': '13308',
        'NAME': 'default',
        'USER': 'root',
        'PASSWORD': '0123456789',
        'TEST': {
            'MIRROR': 'default'
        }
    },
    'sale': {
        'ENGINE': 'django.db.backends.mysql',
        'HOST': '192.168.1.112',
        'PORT': '13306',
        'NAME': 'sale',
        'USER': 'root',
        'PASSWORD': '0123456789',
        'TEST': {
            'MIRROR': 'default'
        }
    },
    'order': {
        'ENGINE': 'django.db.backends.mysql',
        'HOST': '192.168.1.112',
        'PORT': '13307',
        'NAME': 'order',
        'USER': 'root',
        'PASSWORD': '0123456789',
        'TEST': {
            'MIRROR': 'default'
        }
    }
}

分庫以後，在settings.py同級目錄下，建立一個databaserouter

DATABASE_MAPPING = {
    # example:
    # 'app_name':'database_name',
    'sale': 'sale',
    'order': 'order',
    'admin': 'default',
    'auth': 'default',
    'contenttypes': 'default',
    'sessions': 'default',
}


class DBAppsRouter(object):
    def db_for_read(self, model, **hints):
        """"Point all read operations to the specific database."""
        if model._meta.app_label in DATABASE_MAPPING:
            return DATABASE_MAPPING[model._meta.app_label]
        return None

    def db_for_write(self, model, **hints):
        """Point all write operations to the specific database."""
        if model._meta.app_label in DATABASE_MAPPING:
            return DATABASE_MAPPING[model._meta.app_label]
        return None

    def allow_relation(self, obj1, obj2, **hints):
        """Allow any relation between apps that use the same database."""
        db_obj1 = DATABASE_MAPPING.get(obj1._meta.app_label)
        db_obj2 = DATABASE_MAPPING.get(obj2._meta.app_label)
        if db_obj1 and db_obj2:
            if db_obj1 == db_obj2:
                return True
            else:
                return False
        return None

    def allow_syncdb(self, db, model):
        """Make sure that apps only appear in the related database."""

        if db in DATABASE_MAPPING.values():
            return DATABASE_MAPPING.get(model._meta.app_label) == db
        elif model._meta.app_label in DATABASE_MAPPING:
            return False
        return None

    def allow_migrate(self, db, app_label, model=None, **hints):
        """
        Make sure the auth app only appears in the 'auth_db'
        database.
        """
        if db in DATABASE_MAPPING.values():
            return DATABASE_MAPPING.get(app_label) == db
        elif app_label in DATABASE_MAPPING:
            return False
        return None

這裏必定要把DATABASE_MAPPING裏面的app名字和app名字對應，否則會讀寫不到，具體能夠看上述代碼，而後在模型類後面給每一個模型添加一個app_label：

class Meta:
        app_label = 'order'

最後就是migrate數據庫了，先makemigrations order,而後migrate --database order
後面sale app同樣