Question

I m trying to load-test a Rails application using JMeter. A critical part of the application involves a form that includes both text inputs and file uploads. It works fine in a browser, but when I try to post that page in JMeter, Rails is saving all of the parts of the multipart form as temp files, which causes things to break when it s looking for a string and gets a tempfile instead.

It appears that the difference is that, from a browser, the piece of the multipart request that contains a text input looks like this:

-----------------------------7d93b4186074c
Content-Disposition: form-data; name="field_name"

test
-----------------------------7d93b4186074c

while from JMeter it looks like this:

-----------------------------7d159c1302d0y0
Content-Disposition: form-data; name="field_name"
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 8bit

test
-----------------------------7d159c1302d0y0

So apparently Rails sees the former and interprets it as a plain text value and treats it as a string, but sees the latter and saves it to a temp file.

I have not been able to find a setting to convince JMeter not to send the additional headers in the multipart form for non-file fields.

Is there a way to convince Rails to ignore those headers and treat the text/plain text as strings instead of text files? Or a quick way to put a filter in front of my controller that will strip the extra headers?

Alternately, is there a better tool to load-test a Rails application that includes file upload?

Answer 1

There may be a better way, but I ended up adding a quick filter to turn the text/plain tempfiles into strings within the parameter hash:

  def change_text_files_to_strings
    params.each_pair do |key, value|
      params[key] = value.read if (value.class.to_s== Tempfile  && value.content_type.start_with?( text/plain ) )
    end
  end

By the way, it turns out that jmeter is correct here, and rails incorrect: according to RFC 2388, each item in a multipart request should have a content type (not just files), so Rails really shouldn t be using the presence of a content-type header to determine whether it s a file. Ah well.

Answer 2

Turns out these days you can just tick "use browser compatible headers" in JMeter. Could ve saved myself a hell of a lot of time there :-)

Answer 3

So, I have customized JMeter s multipart request posting part in the source code to put out the request that rails understand. The change is easy as shown below but to create compiling Java/JMeter environment took time. :(

Anyways, now I can successfully upload a file by multipart post via JMeter.

in src/protocol/http/org/apache/jmeter/protocol/http/sampler/PostWriter.java

writeStartFileMultipart()
//writeln(out, "Content-Transfer-Encoding: binary"); // $NON-NLS-1$

writeFormMultipart()
/*****
writeln(out, "Content-Type: text/plain; charset=" + charSet); // $NON-NLS-1$
writeln(out, "Content-Transfer-Encoding: 8bit"); // $NON-NLS-1$
*****/

P.S.

A tip tip to create the build environment for 2.4 is

to comment out the 3rd party libraries check in build.xml file.
copy lib/xstream-1.3.1.jar from binary archive into lib/ directory

Answer 4

I also used the solution above as ColdFusion was sending similar headers (minus the Content-Transfer-Encoding) with each piece of form data. I wonder if there s a better way.

EDIT: Anyone know if this has been fixed in Rails 3?

Answer 5

What kind of error do you get? Something like

NoMethodError (undefined method `rewind  for "1":String):

There is an issue with Rack that could explain your problem. See https://github.com/rack/rack/issuesearch?state=open&q=rewind#issue/116

Answer 6

We were also having a similar issue, In addition to the above answers we also correlate the X-CSRF-Token of HTTP Header Manager in that request and were successfully able to upload the required media as many as times we wanted.

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