django – Postgres到Ubuntu Docker容器连接不起作用

[编辑]：我可以在没有任何自己的自定义代码的情况下重现这一点.我刚刚创建了一个运行Ubuntu 14.04的新的Linode映像,并根据 Docker’s website的步骤安装了Docker.

然后我跑了：

docker run -d --name db postgres

并且可以看到它在运行：

$docker ps
CONTAINER ID        IMAGE               COMMAND                CREATED             STATUS              PORTS               NAMES
9d335e8fc70b        postgres            "/docker-entrypoint.   7 minutes ago       Up 7 minutes        5432/tcp            db

然后我启动一个交互式Ubuntu容器,链接到db,并尝试通过nc和curl测试链接：

$docker run -it --link db ubuntu /bin/bash
root@eb02f4e7b89e:/# apt-get install curl
...
root@eb02f4e7b89e:/# curl http://$DB_PORT_5432_TCP_ADDR:$DB_PORT_5432_TCP_PORT/
curl: (7) Failed to connect to 172.17.0.2 port 5432: Connection timed out

我错过了什么？

我正在尝试将postgres容器与运行Django的应用程序容器相关联,但它似乎没有正确链接.

启动容器的命令是：

$docker run -d --name db postgres
$docker run -d --name web --link db -p 8000:80 test_image

这两个容器似乎运行良好：

$docker ps
CONTAINER ID        IMAGE                           COMMAND                CREATED             STATUS              PORTS                  NAMES
5838047eb14c        test_image                      "/test/.docker/st      40 minutes ago      Up 40 minutes       0.0.0.0:8000->80/tcp   web                 
d2d6754430a2        postgres                        "/docker-entrypoint.   44 minutes ago      Up 44 minutes       5432/tcp               db

似乎正确联系：

$docker inspect -f "{{ .HostConfig.Links }}" web
[/db:/web/db]

但是,当我尝试在Web容器中运行“python manage.py migrate”时,它似乎无法连接到postgres容器：

# python manage.py migrate
Traceback (most recent call last):
  File "manage.py",line 10,in <module>
    execute_from_command_line(sys.argv)
  File "/usr/local/lib/python2.7/dist-packages/django/core/management/__init__.py",line 338,in execute_from_command_line
    utility.execute()
  File "/usr/local/lib/python2.7/dist-packages/django/core/management/__init__.py",line 330,in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/usr/local/lib/python2.7/dist-packages/django/core/management/base.py",line 390,in run_from_argv
    self.execute(*args,**cmd_options)
  File "/usr/local/lib/python2.7/dist-packages/django/core/management/base.py",line 441,in execute
    output = self.handle(*args,**options)
  File "/usr/local/lib/python2.7/dist-packages/django/core/management/commands/migrate.py",line 93,in handle
    executor = MigrationExecutor(connection,self.migration_progress_callback)
  File "/usr/local/lib/python2.7/dist-packages/django/db/migrations/executor.py",line 19,in __init__
    self.loader = MigrationLoader(self.connection)
  File "/usr/local/lib/python2.7/dist-packages/django/db/migrations/loader.py",line 47,in __init__
    self.build_graph()
  File "/usr/local/lib/python2.7/dist-packages/django/db/migrations/loader.py",line 180,in build_graph
    self.applied_migrations = recorder.applied_migrations()
  File "/usr/local/lib/python2.7/dist-packages/django/db/migrations/recorder.py",line 59,in applied_migrations
    self.ensure_schema()
  File "/usr/local/lib/python2.7/dist-packages/django/db/migrations/recorder.py",line 49,in ensure_schema
    if self.Migration._meta.db_table in self.connection.introspection.table_names(self.connection.cursor()):
  File "/usr/local/lib/python2.7/dist-packages/django/db/backends/base/base.py",line 164,in cursor
    cursor = self.make_cursor(self._cursor())
  File "/usr/local/lib/python2.7/dist-packages/django/db/backends/base/base.py",line 135,in _cursor
    self.ensure_connection()
  File "/usr/local/lib/python2.7/dist-packages/django/db/backends/base/base.py",line 130,in ensure_connection
    self.connect()
  File "/usr/local/lib/python2.7/dist-packages/django/db/utils.py",line 97,in __exit__
    six.reraise(dj_exc_type,dj_exc_value,traceback)
  File "/usr/local/lib/python2.7/dist-packages/django/db/backends/base/base.py",in ensure_connection
    self.connect()
  File "/usr/local/lib/python2.7/dist-packages/django/db/backends/base/base.py",line 119,in connect
    self.connection = self.get_new_connection(conn_params)
  File "/usr/local/lib/python2.7/dist-packages/django/db/backends/postgresql_psycopg2/base.py",line 172,in get_new_connection
    connection = Database.connect(**conn_params)
  File "/usr/lib/python2.7/dist-packages/psycopg2/__init__.py",line 179,in connect
    connection_factory=connection_factory,async=async)
django.db.utils.OperationalError: could not connect to server: Connection timed out
        Is the server running on host "db" (172.17.0.42) and accepting
        TCP/IP connections on port 5432?

我可以直接连接到postgres容器：

$docker exec -it db bash
root@d2d6754430a2:/# cat /etc/hosts
172.17.0.42     d2d6754430a2
127.0.0.1       localhost
::1     localhost ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
root@d2d6754430a2:/# su postgres
$psql
psql (9.4.4)
Type "help" for help.

postgres=#

但不是来自Web容器内部：

# curl http://$DB_PORT_5432_TCP_ADDR:$DB_PORT_5432_TCP_PORT/
curl: (7) Failed to connect to 172.17.0.42 port 5432: Connection timed out

我的主机正在运行Ubuntu 14.04.

我缺少什么想法？

$docker pull postgres
$docker pull django
$docker run -d --name db -d postgres
$docker run -it --link db:db django bash
root@11c767bd3d09:/#  psql -h db -U postgres
psql (9.4.3,server 9.4.4)
Type "help" for help.

postgres=#

$docker rm $(docker ps -a -q)
$docker images
REPOSITORY          TAG                 IMAGE ID            CREATED             VIRTUAL SIZE
django              latest              29755dd6751b        3 days ago          434.5 MB
postgres            latest              f33438ff9aef        3 days ago          265.5 MB
$docker -v
Docker version 1.7.1,build 786b29d
$docker run -d --name db -d postgres
$docker run -it --link db:db django bash
root@11c767bd3d09:/#  psql -h db -U postgres
psql (9.4.3,server 9.4.4)
Type "help" for help.

postgres=#