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PORails 3 controller receives empty parameters, but only sometimes, after ajax file upload
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copied!<p>Rails 3.2.11</p> <p>I need to upload a whole bunch of large files to a web service. I want to take the files and slice them into smaller chunks, uploading them one by one and then reassemble them on the server. </p> <p>The Javascript (Coffee), work in progress, but it does send the chunks</p> <pre><code>class ChunkUploader constructor: (@file) -> console.debug('wooo') @chunkSize = 1024 * 512 startUpload: -> console.debug('startUpload') this.postChunk(0) postChunk: (index) -> that = this console.debug('postChunk') offset = index * @chunkSize blob = @file.slice(offset, offset + @chunkSize) formData = new FormData() formData.append('utf8','✓') formData.append('authenticity_token', AUTH_TOKEN) formData.append('index', index) formData.append('offset', offset) formData.append('chunk_size', @chunkSize) formData.append('chunk', blob) $.ajax contentType: false processData: false cache: false url: $('#drop_zone').attr('data-action') type: 'POST' data: formData error: -> console.debug('error') success: -> if blob.size < that.chunkSize console.debug("I think we're done") return true else that.postChunk(index + 1) # and then form = document.getElementById 'drop_zone' form.addEventListener 'drop', (e) -> e.stopPropagation() e.preventDefault() files = e.dataTransfer.files cu = new ChunkUploader(files[0]) cu.startUpload() return false </code></pre> <p>The Controller accepting the request is fairly simple so far: </p> <pre><code>def create head params[:chunk].nil? ? :internal_server_error : :ok end </code></pre> <p>The part where I am stuck is that sometimes it works, and sometimes it just doesn't. The inspector in Chrome says the form has been submitted, but Rails refuses to give me the form data. </p> <p>The log (local dev env) then looks like that (notice how the parameters seem absent at the 2nd and 4rth request): </p> <pre><code>17:36:53 logger.1 | Started POST "/admin/products/testproduct/downloads" for 127.0.0.1 at 2013-02-15 17:36:53 +0800 17:36:53 logger.1 | Processing by Admin::DownloadsController#create as */* 17:36:53 logger.1 | Parameters: {"utf8"=>"✓", "authenticity_token"=>"aQCyWZo3vADr5xUBNs1ECC8/bRPXtBxPCuMArXHbJVI=", "index"=>"3", "offset"=>"1572864", "chunk_size"=>"524288", "chunk"=>#<ActionDispatch::Http::UploadedFile:0x007fbedbfc2870 @original_filename="blob", @content_type="application/octet-stream", @headers="Content-Disposition: form-data; name=\"chunk\"; filename=\"blob\"\r\nContent-Type: application/octet-stream\r\n", @tempfile=#<File:/var/folders/t6/wbym5ghx3r3g3ch1wgl1fg640000gn/T/RackMultipart20130215-789-2ckjj9>>, "product_id"=>"testproduct"} 17:36:53 logger.1 | Completed 200 OK in 6ms 17:36:53 logger.1 | 17:36:53 logger.1 | 17:36:53 logger.1 | Started POST "/admin/products/testproduct/downloads" for 127.0.0.1 at 2013-02-15 17:36:53 +0800 17:36:53 logger.1 | Processing by Admin::DownloadsController#create as */* 17:36:53 logger.1 | Parameters: {"product_id"=>"testproduct"} 17:36:53 logger.1 | Completed 500 Internal Server Error in 6ms 17:37:04 logger.1 | 17:37:04 logger.1 | 17:37:04 logger.1 | Started POST "/admin/products/testproduct/downloads" for 127.0.0.1 at 2013-02-15 17:37:04 +0800 17:37:04 logger.1 | Processing by Admin::DownloadsController#create as */* 17:37:04 logger.1 | Parameters: {"utf8"=>"✓", "authenticity_token"=>"aQCyWZo3vADr5xUBNs1ECC8/bRPXtBxPCuMArXHbJVI=", "index"=>"0", "offset"=>"0", "chunk_size"=>"524288", "chunk"=>#<ActionDispatch::Http::UploadedFile:0x007fbedbfbe9a0 @original_filename="blob", @content_type="application/octet-stream", @headers="Content-Disposition: form-data; name=\"chunk\"; filename=\"blob\"\r\nContent-Type: application/octet-stream\r\n", @tempfile=#<File:/var/folders/t6/wbym5ghx3r3g3ch1wgl1fg640000gn/T/RackMultipart20130215-789-154zeln>>, "product_id"=>"testproduct"} 17:37:04 logger.1 | Completed 200 OK in 6ms 17:37:04 logger.1 | 17:37:04 logger.1 | 17:37:04 logger.1 | Started POST "/admin/products/testproduct/downloads" for 127.0.0.1 at 2013-02-15 17:37:04 +0800 17:37:04 logger.1 | Processing by Admin::DownloadsController#create as */* 17:37:04 logger.1 | Parameters: {"product_id"=>"testproduct"} 17:37:04 logger.1 | Completed 500 Internal Server Error in 6ms </code></pre> <p>Sometimes the whole file will upload. Sometimes it chokes on the first segment. Sometimes it breaks in between. I have no idea why this happens and where it breaks. Why is my form sometimes seemingly empty, even though Chrome insists all form data has been created?</p>

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