Community

LTTng is an open source project built by a team of volunteers from around the world.

Most people believe that contributing to an open source project involves writing code, but there are actually multiple other ways to help out. Here are a few ways your help would be greatly appreciated by the LTTng community:

Being an open source project, the LTTng project welcomes contributions from anyone. This guide will walk you through the process of contributing a patch to LTTng.

Get the source code

We use Git to control the versions of the LTTng project. How to use Git is beyond the scope of this guide, but its official website provides many great tutorials. Please refer to the Download section for the official LTTng Git repositories.

Programming style

We use the Linux kernel coding style with one addition for LTTng-tools only: single-line if/for/while control statements must be wrapped in braces.

/* not good */
if (this == that)
    goto fail;

/* good */
if (this == that) {
    goto fail;
}

Although the LTTng code base is primarily written in C, it does contain shell, Perl, Python, and Java code. There is no official coding standard for these languages. However, we encourage you to use a style consistent with the rest of the code written in that language.

Create and send a patch

LTTng's development flow is primarily email-based, although we also accept pull requests on our GitHub mirrors. If you create a GitHub pull request, please make sure you still follow the guidelines below.

Like a lot of open source projects, patches are submitted and reviewed on the project's development mailing list, lttng-dev (lttng-dev@lists.lttng.org). Users and contributors also use the mailing list to share and comment on RFCs and answer questions.

To contribute a patch to the LTTng project:

1. Commit your changes to your local branch.

   The commit's subject (first line) should:

   • Begin with an uppercase letter.
   • Be written in the present tense.
   • Not exceed 72 characters in length.
   • Not end with a period.
   • Be prefixed with Fix: if the commit fixes a bug.

   The commit message's body should be as detailed as possible and explain the reasons behind the proposed change. You must mention any related bug report at the end of the message with the #123 format, where 123 is the bug number:

   • Use Refs: #123 if the patch is related to bug 123, but does not fix it yet.
   • Use Fixes: #123 to indicate that this patch fixes the bug.

   Make sure to sign-off your submitted patches (the -s argument to Git's commit and format-patch commands).

   A patch must be as focused as possible. Do not, for instance, fix a bug and correct the indentation of an unrelated block of code as part of the same patch.

   Here's a complete example:

   Fix: use this instead of that in some context
   
   Ball tip jowl beef ribs shankle, leberkas venison turducken tail pork
   chop t-bone meatball tri-tip. Tongue beef ribs corned beef ball tip
   kevin ground round sausage rump meatloaf pig meatball prosciutto
   landjaeger strip steak. Pork pork belly beef.
   
   Biltong turkey porchetta filet mignon corned beef. T-bone bresaola
   shoulder meatloaf tongue kielbasa.
   
   Fixes: #321
   Refs: #456
   Refs: #4972
   
   Signed-off-by: Janine Sutto <jsutto@janine.su>
   

2. Create one or more patch files corresponding to your Git commits.

   You can use Git's format‑patch command to generate a patch file.

   For example, the following command line generates a patch from the latest commit:

   $

   git format-patch -N1 -s --subject-prefix="PATCH project"

   Replace project with one of:

   • lttng-tools
   • lttng-ust
   • lttng-modules
   • babeltrace (the Babeltrace project uses the LTTng mailing list)

3. If your patch is for the LTTng-tools project, run the checkpatch.pl script on your patch file and correct any reported errors:

   $

   extras/checkpatch.pl --no-tree 0001-Fix...patch

4. Send your patch to the LTTng development mailing list.

   You can use Git's send‑email command to do so:

   $

   git send-email --suppress-cc=self --to=lttng-dev@lists.lttng.org *.patch

   Make sure you are subscribed to the mailing list to follow and take part in discussions about your changes.

   You can also join the file to an email as an attachment if you can't send the patch directly using git send‑email.

Reviews

Once you have posted your patch to the mailing list, or submitted your changes as a GitHub pull request, other contributors may propose modifications to your patch. This is completely normal. This collaborative code review is an integral part of the open source development process in general, and LTTng makes no exception.

Keep in mind that reviewing patches is a time-consuming process. Reviewers may not post comments right away. The current release cycle phase and the complexity of the proposed changes can affect the delays. If you think that we might have forgotten your patch, please mention it on the #lttng IRC channel rather than resubmitting.

Release cycle

The LTTng project follows a release cycle that alternates between development and release candidate (RC) phases. The master branch is feature-frozen during RC phases; only bug fixes are accepted during this period. However, mailing list subscribers may still review patches which add new functionality during an RC phase. We post the upcoming features and release dates in a monthly digest on the mailing list.