django-sharded 0.1.2

快速启动

1. 添加“分片”作为安装的应用程序的第一个条目

   INSTALLED_APPS = [
       'sharded',
       ...
   ]
   

2. 运行python manage.py migrate将Shard.Shard添加到默认数据库

3. [可选]为SHARDED_DB_PREFIX设置一个值默认前缀是shard

   SHARDED_DB_PREFIX = 'shard_'
   

4. 将sharded.db.routers.ShardedRouter添加到数据库路由器设置：

   DATABASE_ROUTERS = ['sharded.db.routers.ShardedRouter',]
   

5. 设置所有可用碎片：

   #NOTE: Django Sharded accesses each shard using the name format '%s%03d' % (SHARDED_DB_PREFIX, n)
   DATABASES['shard_001'] = {
       'ENGINE': 'django.db.backends.postgresql_psycopg2',
       'NAME': 'shard',
       'USER': 'prjdbuser',
       'PASSWORD': 'supersecretpassword',
       'HOST': 'host.for.shard-001.com',
       'PORT': '5432',
   }
   DATABASES['shard_002'] = {
       'ENGINE': 'django.db.backends.postgresql_psycopg2',
       'NAME': 'shard_002',
       'USER': 'prjdbuser',
       'PASSWORD': 'supersecretpassword',
       'HOST': 'host.for.shard-002.com',
       'PORT': '5432',
   }
   DATABASES['shard_003'] = {
       'ENGINE': 'django.db.backends.postgresql_psycopg2',
       'NAME': 'shard_003',
       'USER': 'prjdbuser',
       'PASSWORD': 'supersecretpassword',
       'HOST': 'host.for.shard-002.com',
       'PORT': '5432',
   }
   DATABASES['shard_004'] = {
       'ENGINE': 'django.db.backends.postgresql_psycopg2',
       'NAME': 'shard',
       'USER': 'prjdbuser',
       'PASSWORD': 'supersecretpassword',
       'HOST': 'host.for.shard-004.com',
       'PORT': '5432',
   }
   
   #NOTE: If you use 'dj-database-url' or 'django-connection-url' (shameless self-plug),
   #      you can simplify the above using env vars like DATABASE_SHARD_nnn_URL
   import connection_url
   for shard in xrange(1,256):
       shard = '%s%03d' % ('shard_', shard) #TODO: Use SHARDED_DB_PREFIX if you've customized it above
       shard_env = 'DATABASE_' + shard.upper() + '_URL'
       if shard_env not in os.environ:
           break
       DATABASES.setdefault(shard, connection_url.config(shard_env))
   

6. 使用可选参数运行python manage.py initshard<；1..255>；以初始化碎片

7. 运行python manage.py updateshard<；1..255>；–以字节为单位的容量<；以跟踪碎片中的可用容量

8. 使用shardedmodel作为需要分片的模型的基础。相关模型将自动包含在同一个shard中，ForeignKey字段也将自动使用一个大整数列：

   from sharded.db import models
   from sharded.models import Shard
   
   class HelloManager(models.ShardedManager):
       use_for_related_fields = True
   
       def create(self, **kwargs):
           if not self._db:
               self._db = str(Shard.objects.most_free_shard())
           return super(HelloManager, self).create(**kwargs)
   
   class Hello(models.ShardedModel):
       a_random_field = models.IntegerField()
   
       objects = HelloManager()
   
   class Foo(models.Model):
       hello = models.ForeignKey(Hello)
   
   class Bar(models.Model):
       hello = models.OneToOneField(Hello)
   
   class Baz(models.ShardedModel):
       hello = models.ForeignKey(Hello)
   
   class Herp(models.Model): #Unsharded model
       derp = models.CharField(max_length=8)
   

9. 运行python manage.py makemigrations然后，python manage.py migrate–all在所有碎片上应用迁移

10. 添加要运行的cronjobpython manage.py update shard以定期更新碎片使用级别