Chunked uploader

Description

ClojureScript micro-library that helps you make the process of uploading large files easier for users. It splits file in chunks and uploads them sequentially with retries (and timeouts between them) on failure. Falls back to normal upload if blob slicing isn't supported by user's browser.

Usage

(ns myns.files
  (:require-macros [cljs.core.async.macros :refer [go-loop]])
  (:require [ostronom.uploader :as up]
            [cljs.core.async :refer [<!]]))

(defn i-want-to-upload [file]
  (let [uploader (up/get-uploader)
        ch       (up/upload uploader "/files" file {"form-field" "value"})]
    (go-loop []
      (when-let [[evt data] (<! ch)]
        (cond evt
          :progress
          (do
            (js/console.log "UPLOADED" (:loaded data) "OUT OF" (:total evt))
            (recur))

          :complete
          (js/console.log "DONE")

          :error
          (js/console.log ":(")))))))

get-uploader returns IUploader instance with upload method with two arities: [this target file form-data] and [u target file form-data file-name]

where:

• target is URL where file should be submitted
• file is FormData file instance
• form-data hash-map of additional form data to be sent with a file
• file-name overrides file name of file

You can provide configuration options to get-uploader like this (get-uploader opts), where opts is a hash with some options:

• :file-field form field which should contain file (default: "file")
• :chunk-size size of each chunk in bytes (default: 524288)
• :timeout-fn timeout function which should take number of upload attempt and return number of ms to sleep before another attempt (defaults to constantly 3000 ms)
• :total-field form field which should contain total file size of uploaded file (default: "total")
• :offset-field form field which should contain offset of current chunk from the beginning (default: "offset")
• :max-retries number of retries on chunk upload error. nil value means infinite retries (default: nil)

upload method returns core.async channel with following messages:

• [:complete] -- when upload is complete
• [:error] -- when there was an error after all of the retries
• [:progress {:total N :loaded M}] -- informs you that M out of N bytes are uploaded

Server-side

Obviously, your server should support "gluing" of those chunks together.