Contributing to Simple Bandwidth Scanner

Thank you for your interest in Simple Bandwidth Scanner (sbws).

Examples of contributions include:

  • Bug reports, feature requests
  • Code/documentation patches

Bug reports or feature requests

  • Check that it has not been already reported.

Code/documentation patches

The sbws canonical repository is

To know more about sbws code,

The following are guidelines we aim to follow.

Steps to create a MR

  1. Create a issue in Tor Project Gitlab (Open issue)
  2. Fork sbws via the Gitlab web interface:
  3. Clone the repository locally
  4. Install sbws as explained in ./INSTALL.rst and ./TESTING.rst Use pip install -e <>
  5. If needed install the documentation and build it as explained in ./DOCUMENTATION.rst
  6. Create a new feature branch. If the issue solves a bug, base the branch on the latest maintained version, eg. maint-1.1 and name it with the name of the base branch plus _bugXXX, where XXX is the number of the issue. If the issue is a new feature, base the branch on the master branch and name it ticketXXX. Optionally, the last part of the branch name can be any string, eg. maint-1.1_bugXXX_contributing.
  7. Write code (Code style), tests, documentation, extra files (Extra required files), commit (Commits), etc.
  8. Ensure tests pass (./TESTING.rst).
  9. Push your branch to your Gitlab repository.
  10. Ensure the CI tests are passing (


  1. Create a MR from your branch at

Code style

Follow the Zen of Python (PEP 20)

>>> import this
The Zen of Python, by Tim Peters

Beautiful is better than ugly.
Explicit is better than implicit.
Simple is better than complex.
Complex is better than complicated.
Flat is better than nested.
Sparse is better than dense.
Readability counts.

Code should adhere to the PEP 8 guidelines. Before release 1.0.0, some guidelines have not been followed, such as the ordering the inputs (PEP 8#imports).

External link: Code Style

All functions, methods and classes should have PEP 0257 (except __repr__ and __str__). Before release 1.0.0, some docstrigs do not have 3 double quotes """ (PEP 0257#id15).

External link: Documentation

New features should add a corresponding documentation in /docs.

An editor compatible with EditorConfig will help you to follow the general formatting code style.

Timestamps must be in UTC. It is preferred to use datetime objects or Unix timestamps. Timestamps read by the user should be always formatted in ISO 8601

Functional style is preferred:

  • use list comprenhensions lambda, map, reduce
  • avoid reasigigning variables, instead create new ones
  • use deepcopy when passing list of objects to a function/method
  • classes should change attributes only in one method (other than __init__?)


In general, do not reinvent the wheel, use Python native modules as logging, instead of implementing similar functionality. Or use other packages when the new dependency can be extra, for instance vulture.

Extra required files

Any non-trivial change should contain tests. See ./TESTING.rst. When running tests, currently flake8 informs on some PEP8 errors/warnings, but not all.


Each commit should reference the Tor Project Gitlab issue (example: #12345) and possibly the bugfix version. The commit message should contain Closes: #bugnumber.

From version 1.0.2 we started to prefix the summary with the subpackage or component, though we have not standardized the words to use, eg: scanner, generate, v3bwfile, relaylist, doc, test, CI.

From version 1.0.3, we also started to prefix the summary with new, fix or chg, so that gitchangelog automatically generates different sections in the CHANGELOG.

From version 1.1.0 we started to use the words new, chg and fix, not in the sense gitchangelog use them, but to match semantic versioning changes major, minor and patch.

Try to make each commit a logically separate changes.:

As a general rule, your messages should start with a single line that’s
o more than about 50 characters and that describes the changeset concisely,
followed by a blank line, followed by a more detailed explanation.
The Git project requires that the more detailed explanation include
your motivation for the change and contrast its implementation with
previous behavior — this is a good guideline to follow.
It’s also a good idea to use the imperative present tense in these messages.
In other words, use commands.
Instead of "I added tests for" or "Adding tests for," use "Add tests for."


Template originally written by Tim Pope: example commit

Code being reviewed workflow

When a MR is being reviewed, new changes might be needed:

  • If the change does not modify a previous change, create new commits and push.

  • If the change modifies a previous change and it’s small, git commit fixup should be used. When it is agreed that the MR is ready, create a new branch named mybranch_02 and run:

    rebase --autosquash

    push, create new MR and close old MR mentioning the number of the new MR.

  • If the review takes long and when it’s ready code related to the MR has changed in master, create a new branch named mybranch_02 and run:

    rebase master

    push, create new MR and close old MR mentioning the number of the new MR.


Reviewing code

All code should be peer-reviewed. Two reasons for this are:

Because a developer cannot think of everything at once;
Because a fresh pair of eyes may spot an error, a corner-case in the code,
insufficient documentation, a missing consistency check, etc.



  • Should let the contributor know what to improve/change.
  • Should not push code to the contributor’s branch.
  • Should wait for contributor’s changes or feedback after changes are requested, before merging or closing a MR.
  • Should merge (not rebase) the MR.
  • If rebase is needed due to changes in master, the contributor should create a new branch named xxx_rebased based on the reviewed branch, rebase and create a new MR from it, as explained above.
  • If new changes are needed when the contributor’s branch is ready to merge, the reviewer can create a new branch based on the contributor’s branch, push the changes and merge that MR. The contributor should be notified about it.
  • If the reviewer realize that new changes are needed after the MR has been merged, the reviewer can push to master, notifying the contributor about the changes.
  • Because currently there are not many reviewers, reviewers can merge their own MR if there was not any feedback after a week.
  • Should not push directly to master, unless changes are trivial (typos, extra spaces, etc.)
  • Should not push to master new features while there are open MRs to review.

Currently, the reviewers are gk, ahf, juga.


Releases follow semantic versioning. Until release 1.0.0 is reached, this project is not considered production ready.

Currently development happens in master, this might change from release 1.0.0

so that master has the last release changes, and development happens in the next release branch.

Before major releases, ensure that:

  • Installation from scratch, as specified in ./, must success.

  • All tests must pass.

  • Tor must be able to parse the produced bw files (current way is manual)


    Test that run Tor as dirauth and parse the files

  • Bandwidth files must produce graphs compatible with Torflow (current way to test it is manual)


    Implement something to compare error with current consensus.

  • A dirauth should be able to understand the documentation, otherwise the documentation should be clarified.

Create a ./CHANGELOG.rst file. Each entry should reference the Tor Project Gitlab issue (example: #12345) and possibly the bugfix version. Until version 1.0.2 we have followed keep a changelog format.

From version 1.1.x, run ./scripts/maint/ to create new releases. It uses gitchangelog to automatically add new CHANGELOG entries from the commits’ messages.

Example commit message

Short (50 chars or less) summary of changes

More detailed explanatory text, if necessary.  Wrap it to
about 72 characters or so.  In some contexts, the first
line is treated as the subject of an email and the rest of
the text as the body.  The blank line separating the
summary from the body is critical (unless you omit the body
entirely); tools like rebase can get confused if you run
the two together.

Further paragraphs come after blank lines.

  - Bullet points are okay, too

  - Typically a hyphen or asterisk is used for the bullet,
    preceded by a single space, with blank lines in
    between, but conventions vary here

External references