Impala is an Apache-licensed open-source SQL query engine for data stored in Apache Hadoop clusters. We welcome contributions! This document contains some guidelines for contributing to Impala, and suggestions for the kind of contributions you can make.
What should I contribute?
Some of the most useful contributions to Impala are bug reports. If you discover a bug in Impala, please open a new JIRA ticket at the Impala JIRA tracker (after first checking to see if the bug has already been reported).
Bug reports are best when they contain a precise description of the problem, a minimal set of steps to reproduce the issue, and a comprehensive description of your environment (what version of Impala are you running? Are you using HDFS, S3 or HBase?)
As with other open source communities, the best way to engage is to start small, by fixing some bugs or contributing small features. By doing so, you will earn a reputation as a contributor of high-quality patches, you will get to know the Impala community, and you will become familiar with our process for contribution.
Impala is extremely actively developed, and all parts of the code are changing quickly as we work to meet Impala’s roadmap and provide the features our customers need. We are therefore very unlikely to be able to accept large, unsolicited patches into the codebase. If you are considering undertaking a substantial piece of work, please be forewarned: we cannot guarantee that we will be able to accept it, or that we will have the time to review it. If you are unsure, please ask before you start work.
We also strongly encourage improvements to our developer documentation: we need better build documentation, getting started guides, style guides and more!
How do I contribute code?
Find a JIRA that you would like to work on (or file one if you have discovered a new issue!). If no-one is working on it, assign it to yourself only if you intend to work on it shortly. Ramp-up JIRAs are a great place to look for your first patch ideas.
We may sometimes decide not to accept a proposed feature or bugfix. This does not mean we do not value your contribution, but more likely that we feel that it does not align with the goals of the project or it is not the right time.
Now start coding! As you are writing your patch, please keep the following things in mind:
Finally, please write a good, clear commit message, with a short, descriptive title and a message that is exactly long enough to explain what the problem was, and how it was fixed. Each should have 72 or fewer characters if possible. The first line should have an empty line after it, and the first line should begin with the ticket(s) addressed, followed by a colon and a space: "IMPALA-1234: ". Docs-only commits should have [DOCS] after the ticket numbers, like "IMPALA-1234: [DOCS] ". Here is an example of a good commit message: