最近在做游戏服务分层的时候，一直想把mysql的访问独立成一个单独的服务DBGate，原因如下:

1. 请求收拢到DBGate，可以使DBGate变为无状态的，方便横向扩展

2. 当请求量或者存储量变大时，mysql需要做分库分表，DBGate可以内部直接处理，外界无感知
3. 通过restful限制对数据请求的形式，仅支持简单的get/post/patch/put 进行增删改查，并不支持复杂查询。这个也是和游戏业务的特性有关，如果网站等需要复杂查询的业务，对此并不适合
4. DBGate使用多进程模式，方便控制与mysql之间的链接数，进行mysql访问量阀值保护
5. 方便在DBGate上进行访问量统计，慢查询统计、权限控制等等一系列逻辑
6. 目前是使用python，以后要使用其他语言进行mysql操作时，只要进行标准的http请求即可，不会出现不兼容的情况

当然坏处也是有的：

1. 首当其冲就是单次请求的响应时间变长，毕竟中间加了一层服务，并且还是http格式

2. 部署上比原来复杂了一些，很多对mysql直接操作的思维需要进行转变，一开始可能会有些不适

不过总的来说，还是利大于弊，所以最终还是决定搭建DBGate

当然，我们不可能去手工挨个写每个库表对应的restful服务，值得庆幸的是django和flask都提供了对应的解决方案，我们一个个介绍.
Flask

参考链接: flask-restless

flask-restless使用方法比较简单，我直接贴一下代码即可:

-- coding: utf-8 --

import datetime
from flask import Flask
from flask_sqlalchemy import SQLAlchemy
from flask_restless import APIManager

app = Flask(name)
db = SQLAlchemy(app)
restless = APIManager(app, flask_sqlalchemy_db=db)

class User(db.Model):
"""
user
"""

id = db.Column(db.Integer, primary_key=True)  
username = db.Column(db.String(255), unique=True, nullable=False)  
password = db.Column(db.String(255), nullable=False)  
create_time = db.Column(db.DateTime, nullable=False, default=datetime.datetime.utcnow)  
login_time = db.Column(db.DateTime)

restless.create_api(User, methods=['GET', 'POST', 'DELETE', 'PATCH', 'PUT'], results_per_page=100)

db.create_all()

if name == 'main':
app.run(port=25000)

-- coding: utf-8 --

import datetime
from flask import Flask
from flask_sqlalchemy import SQLAlchemy
from flask_restless import APIManager

app = Flask(name)
db = SQLAlchemy(app)
restless = APIManager(app, flask_sqlalchemy_db=db)

class User(db.Model):
"""
user
"""

id = db.Column(db.Integer, primary_key=True)  
username = db.Column(db.String(255), unique=True, nullable=False)  
password = db.Column(db.String(255), nullable=False)  
create_time = db.Column(db.DateTime, nullable=False, default=datetime.datetime.utcnow)  
login_time = db.Column(db.DateTime)  

restless.create_api(User, methods=['GET', 'POST', 'DELETE', 'PATCH', 'PUT'], results_per_page=100)

db.create_all()

if name == 'main':
app.run(port=25000)

其对应的restful操作如下:

获取用户列表: GET /user
添加用户: POST /user
获取单个用户: GET /user/1
覆盖单个用户: PUT /user/1
修改单个用户: PATCH /user/1

获取用户列表: GET /user
添加用户: POST /user
获取单个用户: GET /user/1
覆盖单个用户: PUT /user/1
修改单个用户: PATCH /user/1

注意:

• 在http请求中，记得加入header: Content-Type: application/json

• flask-restless中，PUT和PATCH一样，都是传入什么字段，只修改什么字段，不会完全覆盖

Django

参考链接: Django REST framework

Django用起来要更复杂一些，也因为django版自带了一个可视化的操作页面，如下:

1. 在settings中添加:

    REST_FRAMEWORK = {
      # Use hyperlinked styles by default.
      # Only used if the `serializer_class` attribute is not set on a view.
      'DEFAULT_MODEL_SERIALIZER_CLASS':
        'rest_framework.serializers.HyperlinkedModelSerializer',

      # Use Django's standard `django.contrib.auth` permissions,
      # or allow read-only access for unauthenticated users.
      'DEFAULT_PERMISSION_CLASSES': [
        #'rest_framework.permissions.DjangoModelPermissionsOrAnonReadOnly',
        'rest_framework.permissions.IsAdminUser',
      ]
    }

    REST_FRAMEWORK = {
      # Use hyperlinked styles by default.
      # Only used if the `serializer_class` attribute is not set on a view.
      'DEFAULT_MODEL_SERIALIZER_CLASS':
        'rest_framework.serializers.HyperlinkedModelSerializer',

      # Use Django's standard `django.contrib.auth` permissions,
      # or allow read-only access for unauthenticated users.
      'DEFAULT_PERMISSION_CLASSES': [
        #'rest_framework.permissions.DjangoModelPermissionsOrAnonReadOnly',
        'rest_framework.permissions.IsAdminUser',
      ]
    }

2. 通过startapp建立一个app: demo
3. 修改demo的models:

    class User(models.Model):
      # key是保留字
      password = models.IntegerField()
      nick = models.CharField(max_length=255)
      create_time = models.DateTimeField(default=datetime.datetime.now)

    class User(models.Model):
      # key是保留字
      password = models.IntegerField()
      nick = models.CharField(max_length=255)
      create_time = models.DateTimeField(default=datetime.datetime.now)

4. 在demo下新建serializers.py

    from rest_framework import serializers  
    from models import User


    class UserSerializer(serializers.ModelSerializer):
      class Meta:
        model = User

    from rest_framework import serializers
    from models import User


    class UserSerializer(serializers.ModelSerializer):
      class Meta:
        model = User

5. 在demo下修改views.py

    from django.shortcuts import render
    from rest_framework import viewsets

    from serializers import UserSerializer
    from models import User


    class UserViewSet(viewsets.ModelViewSet):
      queryset = User.objects.all()
      serializer_class = UserSerializer

    from django.shortcuts import render
    from rest_framework import viewsets

    from serializers import UserSerializer
    from models import User


    class UserViewSet(viewsets.ModelViewSet):
      queryset = User.objects.all()
      serializer_class = UserSerializer

6. 在demo下新建urls.py

    import os.path
    from django.conf.urls import patterns, include, url
    from django.conf.urls.static import static
    from django.conf import settings
    import views

    from rest_framework import routers

    appname = os.path.basename(os.path.dirname(os.path.abspath(__file__)))

    router = routers.DefaultRouter()
    router.register('users', views.UserViewSet, appname)

    urlpatterns = patterns('',
                url(r'^', include(router.urls)),
    )

    import os.path
    from django.conf.urls import patterns, include, url
    from django.conf.urls.static import static
    from django.conf import settings
    import views

    from rest_framework import routers

    appname = os.path.basename(os.path.dirname(os.path.abspath(__file__)))

    router = routers.DefaultRouter()
    router.register('users', views.UserViewSet, appname)

    urlpatterns = patterns('',
                url(r'^', include(router.urls)),
    )

7. 在mysite.urls下include demo.urls和rest_framework.urls

    urlpatterns = patterns('',
      url(r'^demo/', include('demo.urls')),
      url(r'^admin/', include(admin.site.urls)),
      url(r'^api-auth/', include('rest_framework.urls', namespace='rest_framework'))
    )

    urlpatterns = patterns('',
      url(r'^demo/', include('demo.urls')),
      url(r'^admin/', include(admin.site.urls)),
      url(r'^api-auth/', include('rest_framework.urls', namespace='rest_framework'))
    )

8. 执行初始化数据操作:

    python manage.py syncdb

    python manage.py syncdb

之后访问: http://127.0.0.1:8000/demo 即可看到如下界面了:

对应的测试代码如下:

    import json
    import requests
    from urlparse import urljoin

    BASE_URL = 'http://127.0.0.1:16500/'
    AUTH = ('admin', 'admin')


    def test_get_user_list():
      rsp = requests.get(urljoin(BASE_URL, '/demo/users/'), auth=AUTH, headers={
        'Accept': 'application/json'
      })
      assert rsp.ok


    def test_post_user_list():
      json_data = dict(
        password=0,
        nick='oo',
        create_time='2014-03-3T03:3:3'
      )
      rsp = requests.post(urljoin(BASE_URL, '/demo/users/'), auth=AUTH, headers={
        'Accept': 'application/json',
        'Content-Type': 'application/json',
      }, data=json.dumps(json_data))
      assert rsp.ok


    def test_get_user():
      rsp = requests.get(urljoin(BASE_URL, '/demo/users/1'), auth=AUTH, headers={
        'Accept': 'application/json',
        'Content-Type': 'application/json',
      })
      assert rsp.ok


    def test_put_user():
      json_data = dict(
        password=100,
        nick='xx',
        create_time='2014-03-3T03:3:3'
      )
      # 注意最后的 /
      rsp = requests.put(urljoin(BASE_URL, '/demo/users/1/'), auth=AUTH, headers={
        'Accept': 'application/json',
        'Content-Type': 'application/json',
        }, data=json.dumps(json_data),
      )
      assert rsp.ok, rsp.status_code

Django REST framework 是严格区分PUT和PATCH的，这一点和flask-restless 不一样，需要注意。

OK，就这样。