设置静态标头，避免分配？

Question

I am trying to write a Go http handler which is performance sensitive (in particular I want to minimize the amount of RAM used). The handler sets a bunch of headers for each request. All headers are always the same and with the same values. Is there a way to use a single const for all headers and set them all in a single call?

Example. Instead of doing this for all requests:

w.Header().Set("Access-Control-Allow-Origin", "*")
w.Header().Set("Cache-Control", "no-cache")
w.Header().Set("Connection", "keep-alive")

…do something like this:

const staticHeaders = `

Access-Control-Allow-Origin: *
Cache-Control: no-cache
Connection: keep-alive`

w.Headers.WriteRaw(staticHeaders)

Is that possible?

Answer 1

You could hijack the connection, and write the headers directly, but that's only going to save you half the header allocations since the incoming request is still going to allocate a map and strings to fill in the Request struct. It also means that you would need to handle the raw TCP connection yourself from that point forward.

You should profile thoroughly to ensure that the header allocations are actually a bottleneck for your application. There's a lot more overhead to an http request than just the headers.

You can also try alternative http stacks, like github.com/valyala/fasthttp, which strive to minimize allocations.