Cancel a search request in ES

[ESamir]

Add possibility to cancel a search request in ES.

When a request is sent from a web site and the end-user decide to go to another page, we will like to have the possibility to stop the current search .

[dadoonet]

I wonder if you have very loooong running requests.

Otherwise, I don't understand the need for such a feature as most of the time I'd expect search requests running in less than a second.
Can you elaborate a bit more?

[clintongormley]

Duplicate of #12187

[ebuildy]

it's a good idea, I know Nginx has this kind of feature: http://nginx.org/en/docs/http/ngx_http_proxy_module.html#proxy_ignore_client_abort

Determines whether the connection with a proxied server should be closed when a client closes the connection without waiting for a response.

elasticsearch should stop the query if the main HTTP query connection is closed by the client.