部署Django应用至Heroku时migrate命令出现连接错误求助

问题描述 #

我是一名全栈Web开发学生，编程经验尚浅，部署Django到Heroku时遇到以下问题：

• 已将本地数据库从sqlite3迁移至PostgreSQL，本地pgAdmin4显示PostgreSQL服务器端口为5433（旧版本占用了默认的5432端口）
• 本地执行py manage.py runserver完全正常，但执行heroku run python manage.py migrate时抛出错误：django.db.utils.OperationalError: connection to server, port 5433 failed
• 执行heroku create后访问网站出现应用错误，不确定此阶段是否属于正常现象

我的settings.py代码 #

"""
Django settings for recipe_project project.

Generated by 'django-admin startproject' using Django 4.2.7.

For more information on this file, see
https://docs.djangoproject.com/en/4.2/topics/settings/

For the full list of settings and their values, see
https://docs.djangoproject.com/en/4.2/ref/settings/
"""

import os
from pathlib import Path

# Build paths inside the project like this: BASE_DIR / 'subdir'.
BASE_DIR = Path(__file__).resolve().parent.parent


# Quick-start development settings - unsuitable for production
# See https://docs.djangoproject.com/en/4.2/howto/deployment/checklist/

# SECURITY WARNING: keep the secret key used in production secret!
SECRET_KEY = os.environ.get('DJANGO_SECRET_KEY', 'django-insecure-aoc9h$2+(d=$j^d6y5!1i=mc8p2yk)9rj&2woaje1oant$svhv')

# SECURITY WARNING: don't run with debug turned on in production!
DEBUG = False

ALLOWED_HOSTS = ['localhost', '127.0.0.1', '.herokuapp.com']


# Application definition

INSTALLED_APPS = [
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',
    'django.contrib.staticfiles',
    # recipe_project-related apps
    'recipe',
    'user',
]

MIDDLEWARE = [
    'django.middleware.security.SecurityMiddleware',
    'whitenoise.middleware.WhiteNoiseMiddleware',
    'django.contrib.sessions.middleware.SessionMiddleware',
    'django.middleware.common.CommonMiddleware',
    'django.middleware.csrf.CsrfViewMiddleware',
    'django.contrib.auth.middleware.AuthenticationMiddleware',
    'django.contrib.messages.middleware.MessageMiddleware',
    'django.middleware.clickjacking.XFrameOptionsMiddleware',
]

ROOT_URLCONF = 'recipe_project.urls'

TEMPLATES = [
    {
        'BACKEND': 'django.template.backends.django.DjangoTemplates',
        'DIRS': [BASE_DIR / 'templates'],
        'APP_DIRS': True,
        'OPTIONS': {
            'context_processors': [
                'django.template.context_processors.debug',
                'django.template.context_processors.request',
                'django.contrib.auth.context_processors.auth',
                'django.contrib.messages.context_processors.messages',
            ],
        },
    },
]

WSGI_APPLICATION = 'recipe_project.wsgi.application'


# Database
# https://docs.djangoproject.com/en/4.2/ref/settings/#databases

# DATABASES = {
#     'default': {
#         'ENGINE': 'django.db.backends.sqlite3',
#         'NAME': BASE_DIR / 'db.sqlite3',
#     }
# }

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.postgresql_psycopg2',
        'NAME': 'test',
        'USER': 'postgres',
        'PASSWORD': 'password',
        'HOST': 'localhost',
        'PORT': '5432',
    }
}


# Password validation
# https://docs.djangoproject.com/en/4.2/ref/settings/#auth-password-validators

AUTH_PASSWORD_VALIDATORS = [
    {
        'NAME': 'django.contrib.auth.password_validation.UserAttributeSimilarityValidator',
    },
    {
        'NAME': 'django.contrib.auth.password_validation.MinimumLengthValidator',
    },
    {
        'NAME': 'django.contrib.auth.password_validation.CommonPasswordValidator',
    },
    {
        'NAME': 'django.contrib.auth.password_validation.NumericPasswordValidator',
    },
]


# Internationalization
# https://docs.djangoproject.com/en/4.2/topics/i18n/

LANGUAGE_CODE = 'en-us'

TIME_ZONE = 'UTC'

USE_I18N = True

USE_TZ = True


# Static files (CSS, JavaScript, Images)
# https://docs.djangoproject.com/en/4.2/howto/static-files/

STATIC_URL = 'static/'
STATICFILES_DIRS = [BASE_DIR / 'static']

STATIC_ROOT = BASE_DIR / 'staticfiles'
MEDIA_ROOT = os.path.join(BASE_DIR, 'media')
MEDIA_URL = '/media/'


# Default primary key field type
# https://docs.djangoproject.com/en/4.2/ref/settings/#default-auto-field

DEFAULT_AUTO_FIELD = 'django.db.models.BigAutoField'

# Heroku: Update database configuration from $DATABASE_URL.
import dj_database_url
db_from_env = dj_database_url.config(default='postgres://postgres:password@localhost:5433/test')
DATABASES['default'].update(db_from_env)

# DATABASES = {'default': dj_database_url.config(default='postgres://user:pass@localhost/test')}

错误截图 #

问题根源与解决步骤 #

1. 核心问题：本地与云端数据库配置混淆 #

Heroku不会连接你本地的PostgreSQL数据库，它会在云端给你的应用分配独立的PostgreSQL实例。你当前的settings.py存在两个问题：

• 本地配置写的是5432端口，但实际本地用的是5433
• dj_database_url.config的默认值设为本地5433端口，导致部署到Heroku后，代码试图连接本地数据库，这显然不可能

2. 修正settings.py的数据库配置 #

把配置改成区分开发（本地）和生产（Heroku）环境，避免本地配置干扰部署：

import dj_database_url

# 本地开发环境数据库配置（用你实际的本地端口5433）
DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.postgresql_psycopg2',
        'NAME': 'test',
        'USER': 'postgres',
        'PASSWORD': 'password',
        'HOST': 'localhost',
        'PORT': '5433',
    }
}

# 生产环境（Heroku）：仅当存在DATABASE_URL环境变量时，用Heroku提供的配置覆盖
if os.environ.get('DATABASE_URL'):
    db_from_env = dj_database_url.config(conn_max_age=500)
    DATABASES['default'].update(db_from_env)

3. 确保Heroku已添加PostgreSQL插件 #

执行以下命令，给你的Heroku应用分配免费的PostgreSQL实例：

heroku addons:create heroku-postgresql:hobby-dev

这个命令会自动设置DATABASE_URL环境变量，dj_database_url会自动读取该变量配置云端数据库。

4. 重新部署并执行迁移 #

• 提交修改到Git：

git add settings.py
git commit -m "Fix database config for Heroku deployment"
git push heroku main

• 执行云端数据库迁移：

heroku run python manage.py migrate

5. 关于heroku create后的应用错误 #

这个阶段出现错误是正常的——因为数据库还没配置好，应用启动时无法建立数据库连接。完成上面的步骤后，再访问网站就能正常运行了。

内容的提问来源于stack exchange，提问作者jowww