psycopg2.OperationalError：无法翻译主机名“db”（虽然名称“db”在容器中可 ping）

Question

有很多关于类似问题的过时信息，我都经历过。我正在运行 docker-compose 文件版本3.8。我的问题是：

psycopg2 或 Django 无法解析我的数据库的容器名称。

但是，我可以在docker-compose up 之后：

gerard@solace ~$ docker ps
CONTAINER ID        IMAGE                  COMMAND                  CREATED             STATUS              PORTS                    NAMES
21bcbcc35083        project_web            "/app/entrypoint.sh …"   6 seconds ago       Up 6 seconds        0.0.0.0:8006->8000/tcp   project_web_1
a92e3e98477f        postgres:12.0-alpine   "docker-entrypoint.s…"   7 seconds ago       Up 6 seconds        0.0.0.0:5432->5432/tcp   project_db_1

gerard@solace ~$ docker exec -it project_web_1 ping -c 2 db
PING db (172.25.0.2): 56 data bytes
64 bytes from 172.25.0.2: seq=0 ttl=64 time=0.078 ms
64 bytes from 172.25.0.2: seq=1 ttl=64 time=0.302 ms

--- db ping statistics ---
2 packets transmitted, 2 packets received, 0% packet loss
round-trip min/avg/max = 0.078/0.190/0.302 ms```

另外，我的entrypoint.sh 在继续之前连接，并且确实继续，因此主机和端口似乎可以访问：

入口点sn-p：

    while ! nc -z $SQL_HOST $SQL_PORT; do
      sleep 1
    done

我错过了什么？

要完整。我已经“详细”了网络容器中的所有内容，以确保所有内容都来自 .env 文件以及其他内容，并且一切看起来都很好

db_1   | 2020-11-15 14:35:18.557 UTC [1] LOG:  starting PostgreSQL 12.0 on x86_64-pc-linux-musl, compiled by gcc (Alpine 8.3.0) 8.3.0, 64-bit
db_1   | 2020-11-15 14:35:18.557 UTC [1] LOG:  listening on IPv4 address "0.0.0.0", port 5432
db_1   | 2020-11-15 14:35:18.557 UTC [1] LOG:  listening on IPv6 address "::", port 5432
web_1  | Waiting for postgres...
web_1  | PostgreSQL started
db_1   | 2020-11-15 14:35:18.559 UTC [1] LOG:  listening on Unix socket "/var/run/postgresql/.s.PGSQL.5432"
db_1   | 2020-11-15 14:35:18.575 UTC [18] LOG:  database system was shut down at 2020-11-15 14:35:16 UTC
db_1   | 2020-11-15 14:35:18.580 UTC [1] LOG:  database system is ready to accept connections
web_1  | YO: -----------------------------------------
web_1  | SQL_ENGINE ('django.db.backends.postgresql',)
web_1  | SQL_DATABASE ('diff_api_d',)
web_1  | SQL_HOST ('db',)
web_1  | SQL_PORT 5432
web_1  | SQL_USER ('diff_api_u',)
web_1  | SQL_PASSWORD ('diff_api_p',)
web_1  | Traceback (most recent call last):
web_1  |   File "/usr/local/lib/python3.8/site-packages/django/db/backends/base/base.py", line 220, in ensure_connection
web_1  |     self.connect()
web_1  |   File "/usr/local/lib/python3.8/site-packages/django/utils/asyncio.py", line 26, in inner
web_1  |     return func(*args, **kwargs)
web_1  |   File "/usr/local/lib/python3.8/site-packages/django/db/backends/base/base.py", line 197, in connect
web_1  |     self.connection = self.get_new_connection(conn_params)
web_1  |   File "/usr/local/lib/python3.8/site-packages/django/utils/asyncio.py", line 26, in inner
web_1  |     return func(*args, **kwargs)
web_1  |   File "/usr/local/lib/python3.8/site-packages/django/db/backends/postgresql/base.py", line 185, in get_new_connection
web_1  |     connection = Database.connect(**conn_params)
web_1  |   File "/usr/local/lib/python3.8/site-packages/psycopg2/__init__.py", line 127, in connect
web_1  |     conn = _connect(dsn, connection_factory=connection_factory, **kwasync)
web_1  | psycopg2.OperationalError: could not translate host name "('db'" to address: Name does not resolve
web_1  | could not translate host name ")" to address: Name does not resolve

Answer 1

事实证明（如果并非总是如此），这是一个错字。我已将数据库设置从 DATABASES dict 移开，将它们设置在顶部作为单独的声明。

DATABASES = {
    'default': {
        "ENGINE": os.environ.get("SQL_ENGINE", "django.db.backends.sqlite3"),
        "NAME": os.environ.get("SQL_DATABASE", os.path.join(BASE_DIR, "db.sqlite3")),
        "USER": os.environ.get("SQL_USER", "user"),
        "PASSWORD": os.environ.get("SQL_PASSWORD", "password"),
        "HOST": os.environ.get("SQL_HOST", "localhost"),
        "PORT": os.environ.get("SQL_PORT", "5432")
    }
}

问题是我忘了删除结尾的逗号。使它们成为元组而不是字符串。

# check the trailing comma
SQL_HOST = os.environ.get("SQL_HOST"),

感谢阿德里安找到了众所周知的针。