英文:
Golang context in http request when making bulk calls
问题
我正在寻找理解使用Go标准库进行HTTP调用时应该期望的行为。
我了解如果我这样做：
ctx, cancel := context.WithTimeout(context.Background(), 200*time.Millisecond)
defer cancel()
req, err := http.NewRequestWithContext(ctx, http.MethodGet, "http://localhost:8080", nil)
那个特定的请求将在200毫秒内超时。这很好，我明白了。
我的疑问是，如果我这样做：
ctx, cancel := context.WithTimeout(context.Background(), 200*time.Millisecond)
defer cancel()
for i := range 1 to 20 {
req, err := http.NewRequestWithContext(ctx, http.MethodGet, "http://localhost:8080", nil)
}
所以在后面的例子中，我使用同一个上下文进行了一系列的请求。所有的请求会在200毫秒内超时，还是它们会在我开始遍历后的200毫秒后开始失败？
注意：
FATHER_CONTEXT, cancel := context.WithTimeout(context.Background(), 200*time.Millisecond)
defer cancel()
for i := range 1 to 20 {
ctx, cancel := context.WithTimeout(FATHER_CONTEXT, 200*time.Millisecond)
req, err := http.NewRequestWithContext(ctx, http.MethodGet, "http://localhost:8080", nil)
}
英文:
I am looking for to understand the behaviour I should expect when making http calls using go standard library with Context timeout.
I understand that if I do this :
ctx, cancel := context.WithTimeout(context.Background(), 200*time.Millisecond)
defer cancel()
req, err := http.NewRequestWithContext(ctx, http.MethodGet, "http://localhost:8080", nil)
That specific request will TO in 200 milliseconds. That works quite well and I get it.
My doubt is, what happens if I do this:
ctx, cancel := context.WithTimeout(context.Background(), 200*time.Millisecond)
defer cancel()
for loop with a range from 1 to 20 {
req, err := http.NewRequestWithContext(ctx, http.MethodGet, "http://localhost:8080", nil)
}
So in the latter example I am doing a bunch of requests using that very context. Will all requests timeout with 200 milliseconds individually, or will they start to fail after 200 milliseconds have passed from the moment I started ranging over?
Note:
FATHER_CONTEXT, cancel := context.WithTimeout(context.Background(), 200*time.Millisecond)
defer cancel()
for loop with a range from 1 to 20 {
ctx, cancel := context.WithTimeout(FATHER_CONTEXT, 200*time.Millisecond)
req, err := http.NewRequestWithContext(ctx, http.MethodGet, "http://localhost:8080", nil)
}
答案1
得分: 1
从上下文文档中：
> WithCancel、WithDeadline和WithTimeout函数接受一个上下文（父级）并返回一个派生的上下文（子级）和一个CancelFunc。调用CancelFunc会取消子级及其子级，删除父级对子级的引用，并停止任何关联的计时器。
因此，上下文由子级及其子级共享。所有请求将在200毫秒后超时。
英文:
> The WithCancel, WithDeadline, and WithTimeout functions take a Context
> (the parent) and return a derived Context (the child) and a
> CancelFunc. Calling the CancelFunc cancels the child and its children,
> removes the parent's reference to the child, and stops any associated
> timers
So the context is shared by the child and its children. All requests will be timeout after 200 milliseconds.
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