2.14 Limiting Requests
The web-server/dispatchers/limit module provides a wrapper dispatcher that limits how many requests are serviced at once.
(make limit inner [#:over-limit over-limit]) → dispatcher/c limit : number? inner : dispatcher/c over-limit : (symbols 'block 'kill-new 'kill-old) = 'block
Returns a dispatcher that defers to inner for work, but will forward a maximum of limit requests concurrently.
If there are no additional spaces inside the limit and a new request is received, the over-limit option determines what is done.
The default ('block) causes the new request to block until an old request is finished being handled.
If over-limit is 'kill-new, then the new request handler is killed—
Consider this example:
#lang racket (require web-server/web-server web-server/http web-server/http/response (prefix-in limit: web-server/dispatchers/limit) (prefix-in filter: web-server/dispatchers/dispatch-filter) (prefix-in sequencer: web-server/dispatchers/dispatch-sequencer)) (serve #:dispatch (sequencer:make (filter:make #rx"/limited" (limit:make 5 (lambda (conn req) (output-response/method conn (response/full 200 #"Okay" (current-seconds) TEXT/HTML-MIME-TYPE empty (list (string->bytes/utf-8 (format "hello world ~a" (sort (build-list 100000 (λ x (random 1000))) <))))) (request-method req))) #:over-limit 'block)) (lambda (conn req) (output-response/method conn (response/full 200 #"Okay" (current-seconds) TEXT/HTML-MIME-TYPE empty (list #"<html><body>Unlimited</body></html>")) (request-method req)))) #:port 8080) (do-not-return)