一、Changedetection是什么
ChangeDetection-一个用于监控网页内容变化的开源系统。我们先引用开发者对该系统的介绍
changedetection.io - The best and simplest self-hosted free open source website change detection monitoring and notification service. An alternative to Visualping, Watchtower etc. Designed for simplicity - the main goal is to simply monitor which websites had a text change for free. Free Open source web page change detection
来自Github
翻译成中文：
changedetection.io - 最好和最简单的自托管免费开源网站变更检测监控和通知服务。 Visualping、Watchtower 等的替代方案，为简单而设计 - 主要目标是简单地监控哪些网站更改了文本。
哪些场景会用到呢，官方也给出了示例（括号内为大白话版本）：
- 监控产品的价格变化（比如用于淘宝、京东、天猫、亚马逊等电商平台的产品价格监控）
- 政府部门更新（比如监控最新的招投标信息）
- 当您不在他们的邮件列表中时，新软件版本、安全建议（比如跟踪github某项目的最新release版本）
- 有变化的节日（比如监控法定假日？）
- 房源变更（比如某8？）
- 来自政府网站的 COVID 相关新闻（比如本次上海疫情每日的新增病例数）
- 来自他们网站的大学/组织新闻（比如x大学招生动态）
- 检测和监控 JSON API 响应的变化
- JSON API 监控和警报
- 法律和其他文件的变化
- 当文本出现在网站上时通过通知触发 API 调用（比如监控某个一直缺货的商品，在其有库存后发出提醒）
- 使用 JSON 过滤器和 JSON 通知将 API 组合在一起
- 根据 Web 内容的变化创建 RSS 提要
- 监控 HTML 源代码的意外更改，加强您的 PCI 合规性
- 您有一个非常敏感的 URL 列表要监控，并且您不想使用付费的替代方案。 （想白P）
好了言归正传，下面介绍如何在利用宝塔面板搭建这个开源系统。
根据官网的wiki，该系统有多重部署方式，官方推荐的是docker方式，但为了节约vps宝贵的存储资源，我并不想安装在机器上安装docker，所以这里采用另一种方式pip安装。
二、Python环境准备
Changedetection需要python3.7以上版本，所以如果你的python版本低于3.7需要先卸载之前的版本再重新安装新版本。这里需要友情提示一下，宝塔面板其实是自带python2.x的，但记住该版本的python一定不要卸载，否则面板使用有可能出现问题。这里说的卸载低版本是指如果你安装了低版本的python3.x的情况，切记。
（一）、卸载旧版python3.x
例如你之前安装过python3.6，依次执行以下命令进行3.6的卸载
rpm -qa|grep python3|xargs rpm -ev --allmatches --nodeps ##卸载pyhton3
whereis python3 |xargs rm -frv ##删除所有残余文件
卸载完以后我们检查一下系统中现存的python版本
whereis python ##通过此命令查看现有python的位置如果在结果中只有2.x的话证明旧版的3.6已经卸载成功，接下来安装高版本的python，比如我这里选择安装python3.7.5
（二）、安装python
1、下载及安装
wget https://www.python.org/ftp/python/3.7.5/Python-3.7.5.tgz ##下载安装包
tar -xzvf Python-3.7.5.tgz ##解压
cd Python-3.7.5 ##进入文件夹
./configure -prefix=/usr/local/python3.7.5 ##注意：prefix参数用于指定将Python安装在新目录，防止覆盖宝塔系统默认安装的python2.x
make && make install ##编译
2、 建立软链接（python3的环境变量）
这里建立python3的环境变量，作用就是当我们在终端里输入python3这个命令的时候让系统调用刚刚安装的新版python而不是其他版本，命令如下
rm -rf /usr/bin/python3 ##删除原有链接
ln -s /usr/local/python3.7.5/bin/python3.7 /usr/bin/python3 ##建立新的软连接3、 建立软链接（pip的环境变量）
这里建立pip3的环境变量，作用就是当我们在终端里输入pip这个命令的时候让系统调用刚刚安装的新版pip工具而不是其他版本，命令如下
rm -rf /usr/bin/pip ##删除原有链接
ln -s /usr/local/python3.7.5/bin/pip3 /usr/bin/pip ##建立新的软连接执行完之后我们可以用pip -v命令检查下pip版本，如果执行pip命令报错的话可能需要重装一下pip了，命令是
rm -rf /usr/bin/pip ##删除原有链接
python3 get-pip.py --force-reinstall ##强制重装pipOK，到这里整个环境已经搭建好了，下面进入安装
三、安装ChangeDetection
简直不要太简单，直接在终端里面执行以下命令
pip install changedetection.io如果你想安装指定的版本可以用下面的格式
pip install changedetection.io==0.39.12 ##安装0.39.12版本如果想卸载可以使用pip uninstall 这个命令，同样的卸载指定版本的命令是
pip uninstall changedetection.io==0.39.12安装完以后，程序的源码会出现在python安装目录下，如果不需要改源码的话可以不用可以去找了。
不过想要程序运行还需要指定一个额外的目录，比如我们在/www/wwwroot/下新建一个文件夹ChangeDetection，然后执行以下命令让程序跑起来
changedetection.io -d /www/wwwroot/ChangeDetection -p 5000这个命令仅仅在终端里运行是不行的，因为关闭终端它就会中断执行。我们需要使用宝塔里的一个插件——Supervisor管理器
直接去插件市场搜索安装，安装好以后打开管理器将这个命令加入进程守护。
程序跑起来之后访问本地5000端口就可以看到UI界面了，不过我们需要的是外部通过域名来访问它。
四、新建网站，域名反代
我们在宝塔里新建一个网站，添加一个用于这套监控系统的域名，如果有强迫症，可以把网站目录设置为刚刚创建的那个文件夹/www/wwwroot/ChangeDetection，这样就不会多出一个以域名为文件名的目录，然后点开网站配置中的反向代理选项卡
发送域名填写$host，目标url填写127.0.0.1:5000后即可使用域名访问到系统的前端页面。
Bingo!部署成功，接下来根据自己需要添加监控网址吧。
额外说明：如果需要为域名添加SSL证书，即用https访问的话，需要在配置反向代理之前开启SSL，如果你先开了反代再去申请ssl证书会报错，不过问题不大，只需要先把反代暂停一下即可。
关于Changedetection的使用方法，会在后面的文章中更新。（Changedetection在检测到网页内容变化以后可以通过多种方式向你发出通知，比如通过邮件提醒、通过Bark向你的iPhone发送提醒等等）
五、搭建Webdriver服务器（2022.8.11更新）
Centos上安装chrome浏览器以及驱动并用selenium调用的话，因为没有界面，changedetection在调用webdriver抓取数据时会各种报错。
最终放弃该方案，转用docker方式拉取changedetection做好的镜像。具体操作如下：
1、 在宝塔的软件商店里搜索并安装最新的”Docker管理器“
2、 在Docker管理器的“镜像管理”选项卡里点击“获取镜像”，“官方库”里输入镜像名称selenium/standalone-chrome-debug:3.141.59，然后点击“获取镜像”
3、 在“容器列表”选项卡里点击“创建容器”，镜像选择刚刚获取到的镜像文件，绑定IP默认0.0.0.0，端口映射4444:4444，目录映射/dev/shm:/dev/shm，勾选”开机自启“后提交即可启动该镜像
这时webdriver已经运营在本地127.0.0.1:4444端口上了，接下来我们去changedetection里配置
六、 配置WEBDRIVER_URL
Changedetection主程序要调用我们刚刚运行的WEBDRIVER必须要让它知道WEBDRIVER的地址，官方wiki里是以docker运行的changedetection，WEBDRIVER_URL是以环境变量的方式进行配置；但我们这里是采用pip方式安装的changedetection，环境变量不好配置，所以选择直接在源码中修改。
找到/usr/local/python3.7.5/lib/python3.7/site-packages/changedetectionio/conten_fetcher.py文件，定位到
self.command_executor = os.getenv("WEBDRIVER_URL", 'http://browser-chrome/wd/hub').strip('"')直接将WEBDRIVER_URL地址修改为
self.command_executor = os.getenv("WEBDRIVER_URL", 'http://127.0.0.1:4444/wd/hub').strip('"')修改好以后重启一下Changedetection主程序即可，这时再到网站设置里选择内容抓取方式为WebDriver Chrome/Javascript就不会报错了。
七、 配置Bark推送方式
Changedetection集成了Apprise（项目地址https://github.com/caronc/apprise/）作为通知服务，Apprise从v0.9.9版本起支持Bark推送。
如果使用pip安装Changedetection后发现Apprise版本较低无法支持bark推送，可以用以下命令升级
pip install apprise==0.9.9（Changedetection V0.39.14后的版本无需升级）
升级Apprise后就可以在Changedetection的通知里使用bark://{host}:{port}/{device_key} 格式的通知链接将网站变化内容进行推送了。
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