[英]Cancel Http handler request
I have handlers that respond to https requests.我有响应 https 请求的处理程序。 In the handlers I call a function F1() which does some application logic and connects to a mysql db and does a query.在处理程序中,我调用了一个函数 F1(),它执行一些应用程序逻辑并连接到 mysql 数据库并执行查询。 I want to know how I can use the golang context package to cancel the Db query if the client cancels the request.我想知道如果客户端取消请求,我如何使用 golang 上下文包来取消 Db 查询。 Do I need to pass the ctx to F1()?我需要将 ctx 传递给 F1() 吗? Also the code I have now will take 4 seconds even if F1() returns in less then 4. How can I return as soon as F1() returns?此外,即使 F1() 在不到 4 的时间内返回,我现在拥有的代码也将花费 4 秒。如何在 F1() 返回后立即返回?
func handler(w http.ResponseWriter, r *http.Request) {
ctx:= r.context()
F1()
select {
case <-ctx.Done():
case <- time.After( 4*time.Second):
}
w.WriteHeader(http.statusOk)
return
}
To begin, I highly recommend taking a look at the Context blog post to familiarize yourself with contexts, in addition to reading over the context
documentation itself.首先,除了阅读context
文档本身之外,我强烈建议您查看Context 博客文章以熟悉context
。
To address your specific questions:要解决您的具体问题:
How can you cancel the database query if the user cancels their quest?如果用户取消了他们的查询,你如何取消数据库查询?
To make this work, there are a few things you want to check:为了使这项工作正常进行,您需要检查以下几点:
database/sql
) supports context cancellation.确保您的数据库驱动程序(如果您使用database/sql
)支持上下文取消。db.QueryContext
instead of db.Query
).确保您正在使用所有可用方法的 Context 变体(例如db.QueryContext
而不是db.Query
)。Do I need to pass the ctx to F1()?我需要将 ctx 传递给 F1() 吗?
Per #3 above, yes: you will need to pass the context through all intermediate calls to "connect" the database call with the request context.根据上面的#3,是的:您需要通过所有中间调用传递上下文,以将数据库调用与请求上下文“连接”。
How can I return as soon as F1() returns?如何在 F1() 返回后立即返回?
The code that you have in your question calls F1
in series, rather than concurrently, with your cancellation/timeout select
.您在问题中的代码将F1
与您的取消/超时select
一起调用,而不是同时调用。
If you want to apply a specific deadline to your database call, use context.WithTimeout
to limit how long it can take.如果您想对数据库调用应用特定的截止日期,请使用context.WithTimeout
来限制它需要多长时间。 Otherwise, you do not need to do anything special: just call F1
with your context, and the rest will happen for you, no select
is needed.否则,您不需要做任何特别的事情:只需使用您的上下文调用F1
,其余的事情都会为您完成,不需要select
。
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.