英文:
Should we store App Engine Context in a global var versus creating it for every request?
问题
我们目前在每个请求上生成App Engine上下文。我们在其他地方读到过，这并不重要，因为App Engine本质上会缓存上下文。
func addHandler(res http.ResponseWriter, req *http.Request) {
c := appengine.NewContext(req)
}
我们的问题是：将App Engine上下文存储在全局变量中是否有意义？
英文:
We currently generate the App Engine context on every single request. We've read elsewhere, that this doesn't matter as App Engine essentially caches the context anyway.
func addHandler(res http.ResponseWriter, req *http.Request) {
c := appengine.NewContext(req)
Our question: Would it make any sense to store the App Engine context in a global variable?
答案1
得分: 3
我建议不要这样做，原因如下：
-
保持全局状态总是有风险的：它可能变得过时、损坏，总的来说，它会破坏隔离性和封装性。
-
由于AppEngine的工作方式，当你扩展或分布式部署时，你无法真正知道全局变量的全局范围，以及其他请求可能正在读取/写入它。
-
并发性。全局变量是并发性的祸根。为了保持理智，请不要在Web应用程序中使用全局变量。
英文:
I would suggest against it for the following reasons:
-
Keeping global state is always a hazard: it could go stale, corrupted and generally speaking it breaks isolation and encapsulation.
-
Due to the way AppEngine works as you scale up or out, you don't how truly global that global really is and what other requests might be reading/writing to it.
-
Concurrency. Global variables are the bane of concurrency. Save yourselves your sanity and don't use global variables for a web app.
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