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python - Django：子进程连续输出到 HTML 视图

问题描述

我的 Django 应用程序中需要一个 HTML 网页来加载并在可滚动框中显示脚本的连续输出。这可能吗？

我目前正在使用子进程来运行 Python 脚本，但 HTML 页面要等到脚本完成后才会加载（这可能需要大约 5 分钟）。我希望用户看到正在发生的事情，而不仅仅是一个旋转的圆圈。

我已经在文本中使用“\n”卸载了脚本的完整输出；如果可能的话，我希望它输出每个新行。

我的代码如下：

视图.py：

def projectprogress(request):
    GenerateProjectConfig(request)
    home = os.getcwd()
    project_id = request.session['projectname']
    staging_folder = home + "/staging/" + project_id + "/"
    output = ""
    os.chdir(staging_folder)
    script = home + '/webscripts/terraformdeploy.py'
    try:
        output = subprocess.check_output(['python', script], shell=True)
    except subprocess.CalledProcessError:
        exit_code, error_msg = output.returncode, output.output
    os.chdir(home)
    return render(request, 'projectprogress.html', locals())

项目进度.html：

<style>
  div.ex1 {
  background-color: black;
  width: 900px;
  height: 500px;
  overflow: scroll;
  margin: 50px;
}
</style>

<body style="background-color: #565c60; font-family: Georgia, 'Times New Roman', Times, serif; color: white; margin:0"></body>
    <div class="ex1">
        {% if output %}<h3>{{ output }}</h3>{% endif %}
        {% if exit_code %}<h3> The command returned an error: {{ error_msg }}</h3>{% endif %}
    </div>
    <div class="container">
        <a class="button button--wide button--white" href="home.html" title="Home" style="color: white; margin: 60px;">
            <span class="button__inner">
          Home
        </span>
        </a>
    </div>
</body>
</html>

标签： pythonhtmldjangosubprocess

解决方案

您想要的是 websockets，或 Django 中已知的 Channels。

https://channels.readthedocs.io/en/latest/

这允许您将消息从后端发送到前端，而无需在前端拉消息或重新加载页面。

值得一提的是，您还可以将输出流式传输到多个客户端，并将命令发送回您的后端。

为您的代码量身定制的方法

请注意，这是未经测试的，因为我无法访问您的代码，因此您可能需要进行一些小的调整，但我相信提供的代码应该说明这个概念。

设置.py

INSTALLED_APPS = (
#Other installed Apps
       'Channels',
)
CHANNEL_LAYERS = {
      "default": {
          "BACKEND": "asgiref.inmemory.ChannelLayer",
            "ROUTING": "django_channels.routing.channel_routing",
      },
}

routing.py（将文件添加到与 settings.py 相同的文件夹中）

from django_channels_app.consumers import message_ws, listener_add, listener_discconect

channel_routing = [
      route("websocket.receive", message_ws),
      route("websocket.disconnect", listener_discconect),
      route("websocket.connect", listener_add),
]

在您的模块中：

import threading
from channels import Group

class PreserializeThread(threading.Thread):
    def __init__(self, request, *args, **kwargs):
        self.request = request
        super(PreserializeThread, self).__init__(*args, **kwargs)

    def run(self):
        GenerateProjectConfig(request)
        home = os.getcwd()
        project_id = request.session['projectname']
        staging_folder = home + "/staging/" + project_id + "/"
        output = ""
        os.chdir(staging_folder)
        script = home + '/webscripts/terraformdeploy.py'
        try:
            output = subprocess.check_output(['python', script], shell=True)
            Group("django_channels_group").send({
                "text": output,
            })

            # NOTICE THIS WILL BLOCK; 
            # You could try the following, untested snippet


#    proc = subprocess.Popen(['python', script], shell=True, #stdout=subprocess.PIPE)
#    
#    line = proc.stdout.readline()
#    while line:
#        line = proc.stdout.readline()
#        Group("django_channels_group").send({
#                        "text": line,
#                    })
#    Group("django_channels_group").send({
#        "text": "Finished",
#    })
        except subprocess.CalledProcessError:
            exit_code, error_msg = (
                output.returncode,output.output)
        os.chdir(home)

def listener_add(message):
    Group("django_channels_group").add(
        message.reply_channel)

def listener_discconect(message):
    Group("django_channels_group").discard(
        message.reply_channel)

def message_ws(message):
    Group("django_channels_group").send({
          "text": "My group message",
     })

def projectprogress(request):
    ProgressThread(request).start()
    return render(request, 'projectprogress.html', locals())

html

<style>
  div.ex1 {
  background-color: black;
  width: 900px;
  height: 500px;
  overflow: scroll;
  margin: 50px;
}
</style>

<body style="background-color: #565c60; font-family: Georgia, 'Times New Roman', Times, serif; color: white; margin:0"></body>
    <div id="output">
        
    </div>
    <div class="container">
        <a class="button button--wide button--white" href="home.html" title="Home" style="color: white; margin: 60px;">
            <span class="button__inner">
          Home
        </span>
        </a>
    </div>
</body>
</html>

<script>
socket = new WebSocket("ws://127.0.0.1:8000/"); #Or your server IP address
socket.onmessage = function(e) {
    const data = JSON.parse(e.data);
    document.querySelector('#ouput').value += (data.message + '\n');
}
socket.onopen = function() {
    socket.send("Test message");
}
</script>

更通用的答案

后端：

聊天/consumers.py：

import json
from asgiref.sync import async_to_sync
from channels.generic.websocket import WebsocketConsumer

class ChatConsumer(WebsocketConsumer):
    def connect(self):
        self.room_name = self.scope['url_route']['kwargs']['room_name']
        self.room_group_name = 'chat_%s' % self.room_name

        # Join room group
        async_to_sync(self.channel_layer.group_add)(
            self.room_group_name,
            self.channel_name
        )

        self.accept()

    def disconnect(self, close_code):
        # Leave room group
        async_to_sync(self.channel_layer.group_discard)(
            self.room_group_name,
            selfreturn render(request, 'projectprogress.html', locals()).channel_name
        )

    def send_message(self, event):
        message = event['message']

        # Send message to WebSocket
        self.send(text_data=json.dumps({
            'message': message
        }))

我的网站/settings.py：

# Channels
ASGI_APPLICATION = 'mysite.routing.application'
CHANNEL_LAYERS = {
    'default': {
        'BACKEND': 'channels_redis.core.RedisChannelLayer',
        'CONFIG': {
            "hosts": [('127.0.0.1', 6379)],
        },
    },
}

mysite/routing.py：

from channels.auth import AuthMiddlewareStack
from channels.routing import ProtocolTypeRouter, URLRouter
import chat.routing

application = ProtocolTypeRouter({
    # (http->django views is added by default)
    'websocket': AuthMiddlewareStack(
        URLRouter(
            chat.routing.websocket_urlpatterns
        )
    ),
})

聊天/路由.py：

from django.urls import re_path

from . import consumers

websocket_urlpatterns = [
    re_path(r'ws/chat/(?P<room_name>\w+)/$', consumers.ChatConsumer),
]

前端：

<script>
const chatSocket = new WebSocket(
            'ws://'
            + window.location.host
            + '/ws/chat/'
            + roomName
            + '/'
        );

        chatSocket.onmessage = function(e) {
            const data = JSON.parse(e.data);
            document.querySelector('#chat-log').value += (data.message + '\n');
        };
</script>

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