Undertow is a Java web server based on non-blocking IO. It consists of a few different parts:

Code Quality Rank: L2
Programming language: Java
License: Apache License 2.0
Tags: Networking     Server    
Latest version: v2.1.3.Final

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Undertow is a Java web server based on non-blocking IO. It consists of a few different parts:

  • A core HTTP server that supports both blocking and non-blocking IO
  • A Servlet 4.0/5.0 implementation
  • A JSR-356/Jakarta 2.0 compliant Web Socket implementation

Website: http://undertow.io

Issues: https://issues.redhat.com/projects/UNDERTOW

Project Lead: Flavia Rainone [email protected]

Undertow Dev Group: https://groups.google.com/g/undertow-dev/ (you can access archived discussions of old undertow-dev mail list here)

Zulip Chat: https://wildfly.zulipchat.com stream #undertow

Contributing to Undertow - PR Review Process

Bug fixes and documentation improvements are welcome! If you want to contribute and are not sure where to start, I suggest you have a look at our Jira project and get in touch with us via Zulip chat.

PRs must be submitted to master branch (soon to be renamed to main) and they should:

  • state clearly what they do
  • point to associated Jira
  • contain a test case, unless existing tests already verify the code added by the PR
  • have a license header in all new files, with current year’s number
  • pass CI (except for known failures, we are working on fixing those, tracked by UNDERTOW-1523)

If your PR is incomplete, the reviewer might request you add the missing bits or add them for you if that is simple enough.

PR reviewers will take into account the following aspects when reviewing your PR:

  • correctness: the code must be correct
  • performance impact: if there are negative performance impacts in the code, careful consideration must be taken whereas the impact could be eliminated and, in case it cannot, if the new code should be accepted
  • code style: keep your code style consistent with the classes you are editing, such as variable names, ordering of methods, etc
  • scope of the fix: this is a very important factor. Sometimes, the fix should be applied to a broader range of classes, such as a bug that repeats itself in other parts of the code. Other times, the PR solves a bug only partially, because the bug has a broader impact than initially evaluated.
  • is the proposed fix the best approach for the Jira at hand?
  • backwards compatibility: we must prevent any PR that breaks compatibility with previous versions
  • security impact: it is critical to evaluate if the PR has any sort of security impact, preventing the addition of exploitable flaws.

Your PR will be classified by the reviewer with one or more of the following labels: bug fix, enhancement, new feature/API change, and dependency upgrade.

Besides the classifications labels, a series of labels are going to be added to your PR while it is under review. This is the full list of labels and what they mean:

  • waiting CI check PR is ready to be merged, but we are waiting for CI results. The use of this label is optional.
  • waiting PR update reviewer has requested changes to the PR
  • failed CI a new failure was introduced to CI
  • question reviewer has asked one or more questions to the contributor, so the PR can be better assessed
  • under verification reviewer will perform some extra verifications before giving their feedback (usually this means running reproducers, reviewing specs, and the like)
  • waiting peer review PR has been reviewed but is waiting on a second review before being merged (as the changes affects core classes or adds a new feature)
  • next release PR is in the payload of the next release

Notifying Security Relevant Bugs

If you find a bug that has a security impact, please notify us sending an email to Red Hat SecAlert [email protected] with a copy to Flavia Rainone [email protected]. This will ensure the bug is properly handled without causing unnecessary negative impacts for the Undertow's user base.

You can find more information about the security procedures at this page.

*Note that all licence references and agreements mentioned in the Undertow README section above are relevant to that project's source code only.