无法使用 docker compose 使用 postgresql 启动 FastAPI 服务器

Question

我正在使用 Postgresql 作为数据库创建具有简单 CRUD 功能的 FastAPI 服务器。一切都在我当地的环境中运行良好。但是，当我尝试使用docker-compose up 让它在容器中运行时，它失败了。我收到了这个错误：

rest_api_1  |   File "/usr/local/lib/python3.8/site-packages/psycopg2/__init__.py", line 122, in connect
rest_api_1  |     conn = _connect(dsn, connection_factory=connection_factory, **kwasync)
rest_api_1  | sqlalchemy.exc.OperationalError: (psycopg2.OperationalError) could not connect to server: Connection refused
rest_api_1  |   Is the server running on host "db" (172.29.0.2) and accepting
rest_api_1  |   TCP/IP connections on port 5432?
rest_api_1  | 
rest_api_1  | (Background on this error at: https://sqlalche.me/e/14/e3q8)
networks_lab2_rest_api_1 exited with code 1

目录结构：

├── Dockerfile
├── README.md
├── __init__.py
├── app
│   ├── __init__.py
│   ├── __pycache__
│   ├── crud.py
│   ├── database.py
│   ├── main.py
│   ├── models.py
│   ├── object_store
│   └── schemas.py
├── docker-compose.yaml
├── requirements.txt
├── tests
│   ├── __init__.py
│   ├── __pycache__
│   ├── assets
│   ├── test_create.py
│   ├── test_delete.py
│   ├── test_file.py
│   ├── test_get.py
│   ├── test_heartbeat.py
│   └── test_put.py
└── venv
    ├── bin
    ├── include
    ├── lib
    └── pyvenv.cfg

我的docker-compose.yaml

version: "3"

services:
  db:
    image: postgres:13-alpine
    volumes:
      - postgres_data:/var/lib/postgresql/data/
    environment:
      POSTGRES_USER: ${DATABASE_TYPE}
      POSTGRES_PASSWORD: ${DATABASE_PASSWORD}
      POSTGRES_DB: ${DATABASE_NAME}
    ports:
      - "5432:5432"

  rest_api:
    build: .
    command: uvicorn app.main:app --host 0.0.0.0
    env_file:
      - ./.env
    volumes:
      - .:/app
    ports:
      - "8000:8000"
    depends_on:
      - db



volumes:
  postgres_data:

我的 Dockerfile 用于 fastAPI 服务器（在 ./app 下）

FROM python:3.8-slim-buster

RUN apt-get update \
    && apt-get -y install libpq-dev gcc \
    && pip install psycopg2

WORKDIR /app
ENV PYTHONDONTWRITEBYTECODE 1
ENV PYTHONUNBUFFERED 1

COPY requirements.txt .
RUN pip install -r requirements.txt


# copy project
COPY . .

我的database.py

from sqlalchemy import create_engine
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker

from dotenv import load_dotenv
import os


# def create_connection_string():
#     load_dotenv()
#     db_type = os.getenv("DATABASE_TYPE")
#     username = os.getenv("DATABASE_USERNAME")
#     password = os.getenv("DATABASE_PASSWORD")
#     host = os.getenv("DATABASE_HOST")
#     port = os.getenv("DATABASE_PORT")
#     name = os.getenv("DATABASE_NAME")
# 
#     return "{0}://{1}:{2}@{3}/{4}".format(db_type, username, password, host, name)


SQLALCHEMY_DATABASE_URI = "postgresql://postgres:postgres@db:5432/postgres"

engine = create_engine(
    SQLALCHEMY_DATABASE_URI
)
SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)

Base = declarative_base()

我的main.py

from typing import List, Optional
import os, base64, shutil
from functools import wraps

from fastapi import Depends, FastAPI, HTTPException, UploadFile, File, Request, Header
from fastapi.responses import FileResponse
from sqlalchemy.orm import Session

from . import crud, models, schemas
from .database import SessionLocal, engine

models.Base.metadata.create_all(bind=engine)

app = FastAPI()
SECRET_KEY = os.getenv("SECRET")


# Dependency
def get_db():
    db = SessionLocal()
    try:
        yield db
    finally:
        db.close()


def check_request_header(x_token: str = Header(...)):
    if x_token != SECRET_KEY:
        raise HTTPException(status_code=401, detail="Unauthorized")


# endpoints
@app.get("/heartbeat", dependencies=[Depends(check_request_header)], status_code=200)
def heartbeat():
    return "The connection is up"

更完整的日志是：

Creating db_1 ... done
Creating rest_api_1 ... done
Attaching to db_1, rest_api_1
db_1        | The files belonging to this database system will be owned by user "postgres".
db_1        | This user must also own the server process.
db_1        | 
db_1        | The database cluster will be initialized with locale "en_US.utf8".
db_1        | The default database encoding has accordingly been set to "UTF8".
db_1        | The default text search configuration will be set to "english".
db_1        | 

...

db_1        | selecting dynamic shared memory implementation ... posix
db_1        | selecting default max_connections ... 100
db_1        | selecting default shared_buffers ... 128MB
db_1        | selecting default time zone ... UTC
db_1        | creating configuration files ... ok
db_1        | running bootstrap script ... ok
db_1        | performing post-bootstrap initialization ... sh: locale: not found
db_1        | 2021-09-29 18:13:35.027 UTC [31] WARNING:  no usable system locales were found
rest_api_1  | Traceback (most recent call last):
rest_api_1  |   File "/usr/local/lib/python3.8/site-packages/sqlalchemy/engine/base.py", line 3240, in _wrap_pool_connect
rest_api_1  |     return fn()

...

rest_api_1  |   File "/usr/local/lib/python3.8/site-packages/sqlalchemy/engine/default.py", line 584, in connect
rest_api_1  |     return self.dbapi.connect(*cargs, **cparams)
rest_api_1  |   File "/usr/local/lib/python3.8/site-packages/psycopg2/__init__.py", line 122, in connect
rest_api_1  |     conn = _connect(dsn, connection_factory=connection_factory, **kwasync)
rest_api_1  | psycopg2.OperationalError: could not connect to server: Connection refused
rest_api_1  |   Is the server running on host "db" (172.29.0.2) and accepting
rest_api_1  |   TCP/IP connections on port 5432?
rest_api_1  | 
rest_api_1  | 
rest_api_1  | The above exception was the direct cause of the following exception:
rest_api_1  | 
rest_api_1  | Traceback (most recent call last):
rest_api_1  |   File "/usr/local/bin/uvicorn", line 8, in <module>
rest_api_1  |     sys.exit(main())


...


est_api_1  |   File "/usr/local/lib/python3.8/site-packages/sqlalchemy/engine/default.py", line 584, in connect
rest_api_1  |     return self.dbapi.connect(*cargs, **cparams)
rest_api_1  |   File "/usr/local/lib/python3.8/site-packages/psycopg2/__init__.py", line 122, in connect
rest_api_1  |     conn = _connect(dsn, connection_factory=connection_factory, **kwasync)
rest_api_1  | sqlalchemy.exc.OperationalError: (psycopg2.OperationalError) could not connect to server: Connection refused
rest_api_1  |   Is the server running on host "db" (172.29.0.2) and accepting
rest_api_1  |   TCP/IP connections on port 5432?
rest_api_1  | 
rest_api_1  | (Background on this error at: https://sqlalche.me/e/14/e3q8)
rest_api_1 exited with code 1
db_1        | ok
db_1        | syncing data to disk ... ok
db_1        | 
db_1        | 
db_1        | Success. You can now start the database server using:
...

db_1        | 2021-09-29 18:13:36.325 UTC [1] LOG:  starting PostgreSQL 13.4 on x86_64-pc-linux-musl, compiled by gcc (Alpine 10.3.1_git20210424) 10.3.1 20210424, 64-bit
db_1        | 2021-09-29 18:13:36.325 UTC [1] LOG:  listening on IPv4 address "0.0.0.0", port 5432
db_1        | 2021-09-29 18:13:36.325 UTC [1] LOG:  listening on IPv6 address "::", port 5432
db_1        | 2021-09-29 18:13:36.328 UTC [1] LOG:  listening on Unix socket "/var/run/postgresql/.s.PGSQL.5432"
db_1        | 2021-09-29 18:13:36.332 UTC [48] LOG:  database system was shut down at 2021-09-29 18:13:36 UTC
db_1        | 2021-09-29 18:13:36.336 UTC [1] LOG:  database system is ready to accept connections

我进行了非常广泛的搜索并阅读了有关使用docker-compose 运行 FastAPI 服务器和 Postgresql 的文档/教程，例如

https://testdriven.io/blog/fastapi-docker-traefik/ https://github.com/AmishaChordia/FastAPI-PostgreSQL-Docker/blob/master/FastAPI/docker-compose.yml https://www.jeffastor.com/blog/pairing-a-postgresql-db-with-your-dockerized-fastapi-app

他们的方法与我的相同，但它只是不断给我这个Connection refused Is the server running on host "db" (172.29.0.2) and accepting TCP/IP connections on port 5432? 错误消息...

有人可以帮我吗？任何帮助将不胜感激！

Answer 1

首先，database.py 中的SQLALCHEMY_DATABASE_URI 应与您的docker-compose.yaml 中提供的用户、密码和数据库名称相匹配。确保您正在使用正确的环境运行 docker-compose up。在您的情况下，docker-compose up 的环境应该是：

DATABASE_TYPE=postgres
DATABASE_PASSWORD=postgres
DATABASE_NAME=postgres

但我认为您的问题出在其他地方。即使您将您的 API 服务声明为depends_on: - db，postgres 服务器也可能尚未准备好。 depends_on 确保目标图像不会在引用的图像之前实例化，但不确保更多。 postgres 服务器需要一些时间来初始化、启动并在运行的容器中运行，如果您的 API 在此之前尝试连接，它将失败。

常见且最简单的解决方案是编写一堆代码，在实际连接发生之前反复检查数据库是否已启动并运行。由于您没有提供整个回溯（实际上，您已经用... 替换了最重要的部分）我只能猜测触发连接事件的代码行。我建议修改你的database.py 看起来像（未经测试，可能需要一些调整）：

from sqlalchemy import create_engine
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker

from dotenv import load_dotenv
import os
import time

def wait_for_db(db_uri):
    """checks if database connection is established"""

    _local_engine = create_engine(db_uri)

    _LocalSessionLocal = sessionmaker(
        autocommit=False, autoflush=False, bind=_local_engine
    )

    up = False
    while not up:
        try:
            # Try to create session to check if DB is awake
            db_session = _LocalSessionLocal()
            # try some basic query
            db_session.execute("SELECT 1")
            db_session.commit()
        except Exception as err:
            print(f"Connection error: {err}")
            up = False
        else:
            up = True
        
        time.sleep(2)


SQLALCHEMY_DATABASE_URI = "postgresql://postgres:postgres@db:5432/postgres"

wait_for_db(SQLALCHEMY_DATABASE_URI)

engine = create_engine(
    SQLALCHEMY_DATABASE_URI
)
SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)

Base = declarative_base()

更复杂的解决方案是使用 docker-compose healtchecks（仅限 v2）。对于 docker-compose v3，他们建议手动执行，类似于上面介绍的解决方案。

要改进此解决方案，请在 python 命令行脚本中包含wait_for_db，并在预启动阶段在某种图像入口点中运行它。无论如何，您都需要在入口点中有一个预启动阶段来运行迁移（您确实在您的项目中包含迁移，对吗？）