This document is for an in-development version of Galaxy. You can alternatively view this page in the latest release if it exists or view the top of the latest release's documentation.

API Design Guidelines

The following section outlines guidelines related to extending and/or modifying the Galaxy API. The Galaxy API has grown in an ad-hoc fashion over time by many contributors and so clients SHOULD NOT expect the API will conform to these guidelines - but developers contributing to the Galaxy API SHOULD follow these guidelines.

  • API functionality should include docstring documentation for consumption at docs.galaxyproject.org.

  • Developers should familiarize themselves with the HTTP status code definitions http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html. The API responses should properly set the status code according to the result - in particular 2XX responses should be used for successful requests, 4XX for various kinds of client errors, and 5XX for the errors on the server side.

  • If there is an error processing some part of request (one item in a list for instance), the status code should be set to reflect the error and the partial result may or may not be returned depending on the controller - this behavior should be documented.

  • API methods should throw a finite number of exceptions (defined in galaxy.exceptions) and these should subclass MessageException and not paste/wsgi HTTP exceptions. When possible, the framework itself should be responsible catching these exceptions, setting the status code, and building an error response.

  • Error responses should not consist of plain text strings - they should be dictionaries describing the error and containing the following:

      "status_code": 400,
      "err_code": 400007,
      "err_msg": "Request contained invalid parameter, action could not be completed.",
      "type": "error",
      "extra_error_info": "Extra information."

    Various error conditions (once a format has been chosen and framework to enforce it in place) should be spelled out in this document.

  • Backward compatibility is important and should be maintained when possible. If changing behavior in a non-backward compatible way please ensure one of the following holds - there is a strong reason to believe no consumers depend on a behavior, the behavior is effectively broken, or the API method being modified has not been part of a tagged dist release.

The following bullet points represent good practices more than guidelines, please consider them when modifying the API.

  • Functionality should not be copied and pasted between controllers - consider refactoring functionality into associated classes or short of that into Mixins (http://en.wikipedia.org/wiki/Composition_over_inheritance) or into Managers (galaxy.managers).
  • API additions are more permanent changes to Galaxy than many other potential changes and so a second opinion on API changes should be sought.
  • New API functionality should include functional tests. These functional tests should be implemented in Python and placed in test/functional/api.
  • Changes to reflect modifications to the API should be pushed upstream to the BioBlend project if possible.

Longer term goals/notes.

  • It would be advantageous to have a clearer separation of anonymous and admin handling functionality.
  • If at some point in the future, functionality needs to be added that breaks backward compatibility in a significant way to a component used by the community - a “dev” variant of the API will be established and the community should be alerted and given a timeframe for when the old behavior will be replaced with the new behavior.
  • Consistent standards for range-based requests, batch requests, filtered requests, etc… should be established and documented here.