Carrier is a lightweight, async HTTP client built on top of cl-async and fast-http.

Its goal is to allow easy and efficient streaming of data over HTTP. It is the lightweight cousin to drakma-async.


request (function)

(defun request (url &key (method :get) headers body return-body header-callback body-callback finish-callback (redirect 5) redirect-non-get timeout))
  => promise

Perform an HTTP request. Returns a promise (to be used with cl-async-future) that is finished when the response has fully downloaded.

  • url - the URL we're requesting.
  • method - a keyword method (:get, :post, etc). Defaults to :get.
  • headers - a hash table or plist of headers to set with the request. Note that the "Host" header is set automatically (if not proveded) and if the body argument is passed, then "Content-Length" is set as well.
  • body - A string or byte array to send as the HTTP body. If present, will set the "Content-Length" header automatically in the request.
  • return-body - If T, will store the entire HTTP response body and finish the returned promise with it once complete. If this is left nil, then the first value of the finished promise will be nil.
  • header-callback - A function that is called once the headers from the response are fully parsed. The only argument is a hash table of headers.

    (lambda (headers) (gethash "content-type" headers))
  • body-callback - A function that is called once for each chunk of the HTTP response body. The function takes three arguments: a byte array, an index indicating the start of the chunk in the passed byte array, and an index indicating the end of the chunk in the passed byte array. For instance:

    (lambda (chunk start end)
      ;; here's how you'd get the actual bytes. note that most stream functions
      ;; take :start and :end functions, so we don't actually have to do a subseq
      ;; to send the chunk where we need it to go
      (subseq chunk start end))
  • finish-callback - A function of no arguments that is called once the response is completely finished downloading. This gets called just before the returned promise is finished.

    (lambda () ...)
  • redirect - Either nil or an integer value telling Carrier how many redirects (if any) to follow before completing. Default is 5.
  • redirect-non-get - This argument determines whether or not we redirect when performing a request other than a :get or :head. If t, we just redirect blindly until either we hit our destination or the max number of redirects (set by the :redirect arg) is reached. However, :redirect-non-get can also be a function of two arguments (the redirecting URL given in the Location header and the response headers hash table).

    (lambda (redirecting-url headers) ...)
  • timeout - How many seconds to wait for the socket to start reading. If nil (the default), uses the OS default.



Andrew Danger Lyon <>
http client, networking