OpenCPU API wrapper gem
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OpenCPU gem

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Roqua wrapper for the OpenCPU REST API.


Add this line to your application's Gemfile:

gem 'opencpu'

And then execute:

$ bundle

Or install it yourself as:

$ gem install opencpu


OpenCPU.configure do |config|
  config.endpoint_url = ''
  config.timeout      = 30 # Timeout in seconds
  config.verify_ssl   = true # set to false for opencpu server with self-signed certificates.


client = OpenCPU.client


By default we send data using the json format. This format is efficient and safe, but only supports strings and numeric parameters (see opencpu page)

If you want to send R code argument, you'll need to specify format: :urlencoded in your request. Note that you need to enclose your string parameters in quotes in that case, since they will be seen as variables otherwise:

client.execute :digest, :hmac, data: { key: "'foo'", object: "'bar'" }, format: :urlencoded

One-step call

One-step call always returns a JSON result from OpenCPU. This is a preferred way to use this gem, but keep in mind that not every R-package supports one-step responses. On OpenCPU server, packages can be installed under the system, but also under a particular user. This gem also provides a way to access both of them.

Access System Libraries

To get a response from the package installed under the system libraries just pass the package name, function and input data to the function. In the following example :digest is an R-package name, :hmac is a function and { key: 'foo', object: 'bar' } is the input data, where key and object are parameters of hmac function:

client.execute :digest, :hmac, data: { key: 'foo', object: 'bar' }
# => ['0c7a250281315ab863549f66cd8a3a53']

Above example is the same as the following (note the user parameter):

client.execute :digest, :hmac, user: :system, data: { key: 'foo', object: 'bar' }
# => ['0c7a250281315ab863549f66cd8a3a53']

Access User Libraries

To access a package installed under a particular user, just pass user parameter with the name of the existing user.

client.execute :digest, :hmac, user: :johndoe, data: { key: 'foo', object: 'bar' }
# => ['0c7a250281315ab863549f66cd8a3a53']

Two-steps way

To prepare the calculations on OpenCPU execute the #prepare method. It accepts the same arguments as #execute, thus: package, function, user and data.

calculations = client.prepare :animation, 'flip.coin'

calculations variable now holds the reference URL's to the calculations made by OpenCPU. These URL are available through one of the following methods. Which of them are available depends on the package and possible response it can generate.

#graphics(obj, type)
# => Returns the first SVG created by OpenCPU.
# => Returns the second SVG created by OpenCPU., :png)
# => Returns the second PNG created by OpenCPU.


# => Returns the raw output of the R-function.


# => Returns the raw output of stdout being written at the runtime.


# => Returns the warnings returned by the script.


# => Returns the source of the script.


# => Returns the output from R-console.

# => Returns information about R-environment of the script.

Additional features

Multipart requests with files

If you want to send one or more files along, you can pass in a File object as data, but only when using the urlencoded format.

client.execute :foo, :bar, user: :johndoe, data: {file:'/tmp/')}, format: :urlencoded

Package desciption

To access the entire content of a package's DESCRIPTION file

client.description :mypackage
# => "Package: mypackage
#     Version: 1.00
#     ..."


NOTE: Test mode is only supported in combination with #execute and the first step (#prepare) in two-step call.

OpenCPU gem provides a test mode. It basically disables all HTTP interactions with provided OpenCPU server. It is very handy when testing your software for example. You can easily turn it on:


After that you can set fake responses per package/script combination:

OpenCPU.set_fake_response! :digest, :hmac, 'foo'

This will allways return 'foo' when calling function hmac in package digest.



  1. Fork it ( )
  2. Create your feature branch (git checkout -b my-new-feature)
  3. Commit your changes (git commit -am 'Add some feature')
  4. Push to the branch (git push origin my-new-feature)
  5. Create new Pull Request