June 2021
Intermediate to advanced
290 pages
9h 21m
Chinese
Content preview from Node与Express开发（第2版）
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115
第 12章
考虑生产环境中的问题
或许你觉得在目前这个节点就开始讨论生产环境中的问题为时过早，不过如果你提前考
虑，就可以为将来节省大量时间，免去很多麻烦。何况发布到生产环境的日子往往不知不
觉就到了。
本章将学习
Express
如何为不同运行环境提供支持
、扩展网站的方式以及如何监控网站的
运行状态。你会了解如何在测试和开发中模拟生产环境，也会学到如何通过压力测试提前
发现生产环境中的问题。
12.1
运行环境
Express
支持
运行环境
的概念，让你的应用可以在生产、开发或测试模式下运行。实际上，
你想要多少种不同的环境都可以。比如说，你可以有一个准生产环境或一个培训环境。然
而要记住，开发环境、生产环境和测试环境都属于“标准”环境，
Express
和第三方中间件
常常会根据这些环境做决策。换句话说，如果你有一个“准生产”环境，那么是没有办法
让它自动继承生产环境的属性的。为此，建议你还是使用标准的生产、开发和测试环境。
尽管可以通过调用
app.set('env', 'production')
来指定运行环境，但这很不明智，因为
这意味着不论是什么情况，你的应用都会在之前指定的环境中运行。更糟糕的是，应用启
动时是一个环境，而后又切换到了另一个环境。
比较好的做法是使用环境变量
NODE_ENV
来指定运行环境。让我们通过调用
app.get('env')
修改一下应用，让它报告它所在的模式：
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