如何在Rails的响应主体之前发送响应头

Question

Is it possible to generate response headers and send them back to the client without the body?

send_headers
do stuff
render body

Answer 1

No, you cannot respond with headers to the client, perform an operation, and then respond with a body. (I'm not positive this is what you are asking)

If you want to respond to the client and then perform some operation, you could use a background processor, like Sidekiq, to perform the logic after responding to the user but you won't be able to respond again with a body.

Answer 2

To answer the question directly, the headers are a part of the response, so unless you were sending a HEAD request which would only return the headers, you're stuck waiting for the entire response to come back.

To answer the question of long timeouts, there is a common pattern used for dealing with long requests which involves connection polling and the 202 Accepted response code.

You should engineer an endpoint solution that sends a 202 Accepted response straight away and sets the processing chain in motion. With that, you can create a resource which can give a useful estimate of how long the request will take, and where the result will be, and send that in the body of the response.

Your ultimate goal should be to figure out why the request takes so long, but if it is ultimately designed to be a long and arduous response, either due to I/O or CPU time needed, or if it's a business requirement, then using 202 Accepted and setting up a form of connection polling would be your best option.