如何解决Django 1.8在migrate时失败

Posted 2023-04-08

参考技术A 1. 创建项目
运行下面命令就可以创建一个 django 项目，项目名称叫 mysite ：

$ django-admin.py startproject mysite
创建后的项目目录如下：

mysite
├── manage.py
└── mysite
├── __init__.py
├── settings.py
├── urls.py
└── wsgi.py

1 directory, 5 files
说明：

__init__.py ：让 Python 把该目录当成一个开发包 (即一组模块)所需的文件。 这是一个空文件，一般你不需要修改它。
manage.py ：一种命令行工具，允许你以多种方式与该 Django 项目进行交互。 键入python manage.py help，看一下它能做什么。 你应当不需要编辑这个文件；在这个目录下生成它纯是为了方便。
settings.py ：该 Django 项目的设置或配置。
urls.py：Django项目的URL路由设置。目前，它是空的。
wsgi.py：WSGI web 应用服务器的配置文件。更多细节，查看 How to deploy with WSGI
接下来，你可以修改 settings.py 文件，例如：修改 LANGUAGE_CODE、设置时区 TIME_ZONE

SITE_ID = 1

LANGUAGE_CODE = 'zh_CN'

TIME_ZONE = 'Asia/Shanghai'

USE_TZ = True
上面开启了 [Time zone](https://docs.djangoproject.com/en/1.7/topics/i18n/timezones/) 特性，需要安装 pytz：

$ sudo pip install pytz
2. 运行项目
在运行项目之前，我们需要创建数据库和表结构，这里我使用的默认数据库：

$ python manage.py migrate
Operations to perform:
Apply all migrations: admin, contenttypes, auth, sessions
Running migrations:
Applying contenttypes.0001_initial... OK
Applying auth.0001_initial... OK
Applying admin.0001_initial... OK
Applying sessions.0001_initial... OK
然后启动服务：

$ python manage.py runserver
你会看到下面的输出：

Performing system checks...

System check identified no issues (0 silenced).
January 28, 2015 - 02:08:33
Django version 1.7.1, using settings 'mysite.settings'
Starting development server at http://127.0.0.1:8000/
Quit the server with CONTROL-C.
这将会在端口8000启动一个本地服务器, 并且只能从你的这台电脑连接和访问。 既然服务器已经运行起来了，现在用网页浏览器访问 http://127.0.0.1:8000/。你应该可以看到一个令人赏心悦目的淡蓝色 Django 欢迎页面它开始工作了。

你也可以指定启动端口:

$ python manage.py runserver 8080
以及指定 ip：

$ python manage.py runserver 0.0.0.0:8000
3. 创建 app
前面创建了一个项目并且成功运行，现在来创建一个 app，一个 app 相当于项目的一个子模块。

在项目目录下创建一个 app：

$ python manage.py startapp polls
如果操作成功，你会在 mysite 文件夹下看到已经多了一个叫 polls 的文件夹，目录结构如下：

polls
├── __init__.py
├── admin.py
├── migrations
│ └── __init__.py
├── models.py
├── tests.py
└── views.py

1 directory, 6 files
4. 创建模型
每一个 Django Model 都继承自 django.db.models.Model
在 Model 当中每一个属性 attribute 都代表一个 database field
通过 Django Model API 可以执行数据库的增删改查, 而不需要写一些数据库的查询语句
打开 polls 文件夹下的 models.py 文件。创建两个模型：

import datetime
from django.db import models
from django.utils import timezone

class Question(models.Model):
question_text = models.CharField(max_length=200)
pub_date = models.DateTimeField('date published')

def was_published_recently(self):
return self.pub_date >= timezone.now() - datetime.timedelta(days=1)

class Choice(models.Model):
question = models.ForeignKey(Question)
choice_text = models.CharField(max_length=200)
votes = models.IntegerField(default=0)
然后在 mysite/settings.py 中修改 INSTALLED_APPS 添加 polls：

INSTALLED_APPS = (
'django.contrib.admin',
'django.contrib.auth',
'django.contrib.contenttypes',
'django.contrib.sessions',
'django.contrib.messages',
'django.contrib.staticfiles',
'polls',
)
在添加了新的 app 之后，我们需要运行下面命令告诉 Django 你的模型做了改变，需要迁移数据库：

$ python manage.py makemigrations polls
你会看到下面的输出日志：

Migrations for 'polls':
0001_initial.py:
- Create model Choice
- Create model Question
- Add field question to choice
你可以从 polls/migrations/0001_initial.py 查看迁移语句。

运行下面语句，你可以查看迁移的 sql 语句：

$ python manage.py sqlmigrate polls 0001
输出结果：

BEGIN;
CREATE TABLE "polls_choice" ("id" integer NOT NULL PRIMARY KEY AUTOINCREMENT, "choice_text" varchar(200) NOT NULL, "votes" integer NOT NULL);
CREATE TABLE "polls_question" ("id" integer NOT NULL PRIMARY KEY AUTOINCREMENT, "question_text" varchar(200) NOT NULL, "pub_date" datetime NOT NULL);
CREATE TABLE "polls_choice__new" ("id" integer NOT NULL PRIMARY KEY AUTOINCREMENT, "choice_text" varchar(200) NOT NULL, "votes" integer NOT NULL, "question_id" integer NOT NULL REFERENCES "polls_question" ("id"));
INSERT INTO "polls_choice__new" ("choice_text", "votes", "id") SELECT "choice_text", "votes", "id" FROM "polls_choice";
DROP TABLE "polls_choice";
ALTER TABLE "polls_choice__new" RENAME TO "polls_choice";
CREATE INDEX polls_choice_7aa0f6ee ON "polls_choice" ("question_id");

COMMIT;
你可以运行下面命令，来检查数据库是否有问题：

$ python manage.py check
再次运行下面的命令，来创建新添加的模型：

$ python manage.py migrate
Operations to perform:
Apply all migrations: admin, contenttypes, polls, auth, sessions
Running migrations:
Applying polls.0001_initial... OK
总结一下，当修改一个模型时，需要做以下几个步骤：

修改 models.py 文件
运行 python manage.py makemigrations 创建迁移语句
运行 python manage.py migrate，将模型的改变迁移到数据库中
你可以阅读 django-admin.py documentation，查看更多 manage.py 的用法。

创建了模型之后，我们可以通过 Django 提供的 API 来做测试。运行下面命令可以进入到 python shell 的交互模式：

$ python manage.py shell
下面是一些测试：

>>> from polls.models import Question, Choice # Import the model classes we just wrote.

# No questions are in the system yet.
>>> Question.objects.all()
[]

# Create a new Question.
# Support for time zones is enabled in the default settings file, so
# Django expects a datetime with tzinfo for pub_date. Use timezone.now()
# instead of datetime.datetime.now() and it will do the right thing.
>>> from django.utils import timezone
>>> q = Question(question_text="What's new?", pub_date=timezone.now())

# Save the object into the database. You have to call save() explicitly.
>>> q.save()

# Now it has an ID. Note that this might say "1L" instead of "1", depending
# on which database you're using. That's no biggie; it just means your
# database backend prefers to return integers as Python long integer
# objects.
>>> q.id
1

# Access model field values via Python attributes.
>>> q.question_text
"What's new?"
>>> q.pub_date
datetime.datetime(2012, 2, 26, 13, 0, 0, 775217, tzinfo=<UTC>)

# Change values by changing the attributes, then calling save().
>>> q.question_text = "What's up?"
>>> q.save()

# objects.all() displays all the questions in the database.
>>> Question.objects.all()
[<Question: Question object>]
打印所有的 Question 时，输出的结果是 [<Question: Question object>]，我们可以修改模型类，使其输出更为易懂的描述。修改模型类：

from django.db import models

class Question(models.Model):
# ...
def __str__(self): # __unicode__ on Python 2
return self.question_text

class Choice(models.Model):
# ...
def __str__(self): # __unicode__ on Python 2
return self.choice_text
接下来继续测试：

>>> from polls.models import Question, Choice

# Make sure our __str__() addition worked.
>>> Question.objects.all()
[<Question: What's up?>]

# Django provides a rich database lookup API that's entirely driven by
# keyword arguments.
>>> Question.objects.filter(id=1)
[<Question: What's up?>]
>>> Question.objects.filter(question_text__startswith='What')
[<Question: What's up?>]

# Get the question that was published this year.
>>> from django.utils import timezone
>>> current_year = timezone.now().year
>>> Question.objects.get(pub_date__year=current_year)
<Question: What's up?>

# Request an ID that doesn't exist, this will raise an exception.
>>> Question.objects.get(id=2)
Traceback (most recent call last):
...
DoesNotExist: Question matching query does not exist.

# Lookup by a primary key is the most common case, so Django provides a
# shortcut for primary-key exact lookups.
# The following is identical to Question.objects.get(id=1).
>>> Question.objects.get(pk=1)
<Question: What's up?>

# Make sure our custom method worked.
>>> q = Question.objects.get(pk=1)

# Give the Question a couple of Choices. The create call constructs a new
# Choice object, does the INSERT statement, adds the choice to the set
# of available choices and returns the new Choice object. Django creates
# a set to hold the "other side" of a ForeignKey relation
# (e.g. a question's choice) which can be accessed via the API.
>>> q = Question.objects.get(pk=1)

# Display any choices from the related object set -- none so far.
>>> q.choice_set.all()
[]

# Create three choices.
>>> q.choice_set.create(choice_text='Not much', votes=0)
<Choice: Not much>
>>> q.choice_set.create(choice_text='The sky', votes=0)
<Choice: The sky>
>>> c = q.choice_set.create(choice_text='Just hacking again', votes=0)

# Choice objects have API access to their related Question objects.
>>> c.question
<Question: What's up?>

# And vice versa: Question objects get access to Choice objects.
>>> q.choice_set.all()
[<Choice: Not much>, <Choice: The sky>, <Choice: Just hacking again>]
>>> q.choice_set.count()
3

# The API automatically follows relationships as far as you need.
# Use double underscores to separate relationships.
# This works as many levels deep as you want; there's no limit.
# Find all Choices for any question whose pub_date is in this year
# (reusing the 'current_year' variable we created above).
>>> Choice.objects.filter(question__pub_date__year=current_year)
[<Choice: Not much>, <Choice: The sky>, <Choice: Just hacking again>]

# Let's delete one of the choices. Use delete() for that.
>>> c = q.choice_set.filter(choice_text__startswith='Just hacking')
>>> c.delete()
>>>
上面这部分测试，涉及到 django orm 相关的知识，详细说明可以参考 Django中的ORM。

5. 管理 admin
Django有一个优秀的特性, 内置了Django admin后台管理界面, 方便管理者进行添加和删除网站的内容.

新建的项目系统已经为我们设置好了后台管理功能，见 mysite/settings.py：

INSTALLED_APPS = (
'django.contrib.admin', #默认添加后台管理功能
'django.contrib.auth',
'django.contrib.contenttypes',
'django.contrib.sessions',
'django.contrib.messages',
'django.contrib.staticfiles',
'mysite',
)
同时也已经添加了进入后台管理的 url, 可以在 mysite/urls.py 中查看：

url(r'^admin/', include(admin.site.urls)), #可以使用设置好的url进入网站后台
接下来我们需要创建一个管理用户来登录 admin 后台管理界面：

$ python manage.py createsuperuser
Username (leave blank to use 'june'): admin
Email address:
Password:
Password (again):
Superuser created successfully.
总结
最后，来看项目目录结构：

mysite
├── db.sqlite3
├── manage.py
├── mysite
│ ├── __init__.py
│ ├── settings.py
│ ├── urls.py
│ ├── wsgi.py
├── polls
│ ├── __init__.py
│ ├── admin.py
│ ├── migrations
│ │ ├── 0001_initial.py
│ │ ├── __init__.py
│ ├── models.py
│ ├── templates
│ │ └── polls
│ │ ├── detail.html
│ │ ├── index.html
│ │ └── results.html
│ ├── tests.py
│ ├── urls.py
│ ├── views.py
└── templates
└── admin
└── base_site.htm

如何解决 AWS Elastic Beanstalk Django 运行状况检查问题

【中文标题】如何解决 AWS Elastic Beanstalk Django 运行状况检查问题

【英文标题】：How to resolve AWS Elastic Beanstalk Django health check problems

【发布时间】：2020-11-10 15:18:22

【问题描述】：

我最近将我的 Django API 后端部署到 AWS EB 到他们的 Linux 2 系统（确切的平台名称是 Python 3.7 running on 64bit Amazon Linux 2）。

几乎一切都按预期工作，但我的应用程序运行状况为 Severe，经过数小时的调试后，我不知道为什么。

正在使用以下端点（django-health-check 模块）处理应用程序的运行状况检查。

url(r'^ht/', include('health_check.urls'))

100% 的请求的状态代码为 200，但我的整体健康状况如下：

|--------------------|----------------|---------------------------------------------------|
|   instance-id      |   status       |   cause                                           |
|--------------------|----------------|---------------------------------------------------|
|   Overall          |   Degraded     |   Impaired services on all instances.             |
|   i-0eb89f...      |   Severe       |   Following services are not running: release.    |
|--------------------|----------------|---------------------------------------------------|

最奇怪的是Following services are not running: release.的消息是互联网独有的（似乎以前没有人遇到过这样的问题）。

另一个奇怪的事情是我的/var/log/healthd/daemon.log 文件的内容类似于

W, [2020-07-21T09:00:01.209091 #3467]  WARN -- : log file "/var/log/nginx/healthd/application.log.2020-07-21-09" does not exist

时间变化的地方。

最后可能相关的是我在.ebextensions 目录中的单个文件的内容：

option_settings:
  "aws:elasticbeanstalk:application:environment":
    DJANGO_SETTINGS_MODULE: "app.settings"
    "PYTHONPATH": "/var/app/current:$PYTHONPATH"
  "aws:elasticbeanstalk:container:python":
    WSGIPath: app.wsgi:application
    NumProcesses: 3
    NumThreads: 20
  aws:elasticbeanstalk:environment:proxy:staticfiles:
    /static: static
    /static_files: static_files
container_commands:
  01_migrate:
    command: "source /var/app/venv/staging-LQM1lest/bin/activate && python manage.py migrate --noinput"
    leader_only: true
packages:
  yum:
    git: []
    postgresql-devel: []

有谁知道如何解决这个问题？最终目标是拥有绿色OK健康。

---

编辑：最后我切换到Basic 卫生系统，问题突然消失了。不过，我仍然有兴趣解决最初的问题，因为 Enhanced 卫生系统提供了一些好处

【问题讨论】：

是负载均衡的环境吗？

@Marcin 是的，我也忘了提到我正在使用Enhanced health reporting and monitoring

应用程序是否完全按预期工作？ /var/log/cloud-init-cmd 等日志不显示错误？

@Marcin 我的意思是端点和数据库都工作得很好。我从 EB 控制台下载了完整的日志并浏览了它们。我发现的只是 eb-engine.log 中的 2 个似乎不相关的错误（[ERROR] nginx: the configuration file /var/proxy/staging/nginx/nginx.conf syntax is ok nginx: configuration file /var/proxy/staging/nginx/nginx.conf test is successful 和 [ERROR] Created symlink from /etc/systemd/system/multi-user.target.wants/worker.service to /etc/systemd/system/worker.service.）。一个名为 cloud-init-cmd 的文件甚至不是日志的一部分。

@Marcin 我也切换到Basic 卫生系统（而不是Enhanced），问题就消失了。不过，我仍然有兴趣解决原来的问题。

【参考方案1】：

我认为您遇到的问题可能是由于文件 settings.py 中的 ALLOWED_HOSTS 设置造成的。

EB 向您的应用程序发送一个 HTTP 请求以查看其是否正常工作，但 Django 会阻止任何不是来自设置变量中指定主机的通信。但是这里有一个问题，EB将请求发送到ec2实例的私有ip。

解决此问题的最简单方法是在您的settings.py 文件中允许所有这样的主机：

ALLOWED_HOSTS=['*']

这可能会导致安全问题，但这是最快的方法。现在，为了使其动态工作，因为 ec2 实例可以随时启动，私有 ip 从一个实例更改为另一个实例。

要解决这个问题，您必须在部署过程开始时获取私有 IP。

在settings.py 的顶部放置以下函数：

import os
import requests
# Other imports ...

def is_ec2_linux():
"""Detect if we are running on an EC2 Linux Instance
   See http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/identify_ec2_instances.html
"""
    if os.path.isfile("/sys/hypervisor/uuid"):
        with open("/sys/hypervisor/uuid") as f:
            uuid = f.read()
            return uuid.startswith("ec2")
    return False

def get_token():
"""Set the autorization token to live for 6 hours (maximum)"""
    headers = 
        'X-aws-ec2-metadata-token-ttl-seconds': '21600',
    
    response = requests.put('http://169.254.169.254/latest/api/token', headers=headers)
    return response.text


def get_linux_ec2_private_ip():
    """Get the private IP Address of the machine if running on an EC2 linux server.
See https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/instancedata-data-retrieval.html"""

    if not is_ec2_linux():
        return None
    try:
        token = get_token()
        headers = 
            'X-aws-ec2-metadata-token': f"token",
        
        response = requests.get('http://169.254.169.254/latest/meta-data/local-ipv4', headers=headers)
        return response.text
    except:
        return None
    finally:
        if response:
            response.close()
# Other settings

最重要的函数是get_token()和get_linux_ec2_private_ip()，第一个设置访问令牌并检索它，以便第二个使用它并获取当前的ec2实例IP。

检索到它后，将其添加到您的 ALLOWED_HOSTS

ALLOWED_HOSTS = ['127.0.0.1', 'mywebsite.com']
private_ip = get_linux_ec2_private_ip()
if private_ip:
   ALLOWED_HOSTS.append(private_ip)

之后，只需提交您的更改并使用 eb deploy 重新部署它（如果您已设置 EB CLI）。