The Arrow project uses JIRA as a bug tracker. To report a bug, you'll have to first create an account on the Apache Foundation JIRA. The JIRA server hosts bugs and issues for multiple Apache projects. The JIRA project name for Arrow is "ARROW".
Before you create a new bug entry, we recommend you first search among existing Arrow issues.
When you create a new JIRA entry, please don't forget to fill the "Component" field. Arrow has many subcomponents and this helps triaging and filtering tremendously. Also, we conventionally prefix the issue title with the component name in brackets, such as "[C++] Crash in Array::Frobnicate()", so as to make lists more easy to navigate, and we'd be grateful if you did the same.
First create a JIRA entry as described above. Then, submit your changes as a Github Pull Request. We'll ask you to prefix the pull request title with the JIRA issue number and the component name in brackets. (for example: "ARROW-2345: [C++] Fix crash in Array::Frobnicate()"). Respecting this convention makes it easier for us to process the backlog of submitted Pull Requests.
We ask that all discussions about major changes in the codebase happen publicly on the arrow-dev mailing-list.
You can also ask on the mailing-list, see above.
Please read our development documentation.