How to contribute to Apache NiFi
We are always excited to have contributions from the community - especially from new contributors!
We are interested in accepting contributions of code, as well as documentation and even artwork that can be applied as icons or styling to the application.
Documentation is created in AsciiDoc.
Running NiFi in Debug mode
While NiFi Mock library can greatly simplify your development and testing efforts, some times it is still necessary to be able to set breakpoints and debug your code within the running instance of NiFi. To do that NiFi needs to be started in Debug mode within your IDE. Please follow the instructions provided in the NiFi IDE Integration module.
Where to Start?
Finding Issues and Extending the Project
NiFi's JIRA page can be used to find tickets that are tagged as "beginner", or you can dig into any of the tickets for creating Processors. Processors should be self-contained and not rely on other outside components (except for Controller Services), so they make for excellent starting points for new NiFi developers to get started. This exposes the developer to the NiFi API and is the most extensible part of the dataflow system. The NiFi Developer Guide provides details on how to get started with the NiFi API as well as best practices and common approaches to component design.
We have additionally created filters that show various types of issues available to be worked:
System-level and overview documentation such as:
- Administration Guide,
- Developer's Guide,
- User's Guide,
Are located in
'<code checkout location>/nifi-docs/src/main/asciidoc' and can be changed by making changes to the ASCIIdoc files and following the code contribution process described in "Providing code or documentation contributions" section of this document.
Tools available to facilitate documentation generation are available at Editing AsciiDoc with Live Preview.
Component level documentation can be contributed to by making direct modifications to the source code of the relevant component. Generally the documentation of components is performed by adding the relevant details to the following annotations
and the description field of annotations such as:
and the description method of Component Properties and Relationships
When the documentation of a processor is particularly complex (e.g, may include very long descriptions or images), a contributor may chose to use NiFi's capability to automatically link additional documentation to a processor.
In this case the contributor may extend documentation by performing changes to
'additionalDetails.html'. As described in the Developer's Guide, this file should exist within a directory whose name is the fully-qualified name of the Processor, and this directory’s parent should be named docs and exist in the
'resources' directory of a particular processor bundle.
As with other contributions, component level documentation should follow the process described in "Providing code or documentation contributions" section of this document.
Create a ticket for new bugs or features
Run into a bug or think there is something that would benefit the project? Regardless if you have the time to provide the fix or implementation, we encourage any such items to be filed as an issue at the Apache NiFi JIRA.
Providing code or documentation contributions
The source is hosted at
Configure your git client
Ensure your git user name and email are configured
The following lines ensure your commits are appropriately annotated with your information
git config --global user.name "User Name"
git config --global user.email firstname.lastname@example.org
Windows Specific configuration
The following options provide handling of long file paths that can be troublesome as well as not using Windows style line returns.
git config --global core.longpaths true
git config --global core.autocrlf false
Clone a copy of the repository
From the Apache Hosted Repository
From the GitHub Mirror
git clone https://github.com/apache/nifi.git
From your GitHub Fork
git clone email@example.com:<account name>/nifi.git
Retrieval of upstream changes
Additionally, it is beneficial to add a git remote for the mirror to allow the retrieval of upstream changes
git remote add upstream https://github.com/apache/nifi.git
Checkout the 'master' or '0.x' branch
git checkout -b master origin/master will create a local, tracking branch named
git checkout -b 0.x origin/0.x will create a local, tracking branch named
The master branch currently represents the next major release line (1.x). Substantial work here is underway to improve the NiFi's core framework and UI. If you're interested in building the 0.x baseline which is still actively released to include new components and bug fixes, please checkout the 0.x branch. Ultimately contributions will need to be applied to both branches in order to be included in subsequent releases.
The NiFi community uses a modified Gitflow development model. A summary:
- Use of a central repository
- Branch per feature similar to the Feature Branch Workflow
- Work is done locally and then pushed to the central repo
- 'master' branch contains the official release history. Code changes (not code formatting, administrative updates) require Review-Then-Commit (RTC) by another committer to get incorporated.
Perform your code changes
Create a feature branch
Typically, there is a 1-to-1 mapping of a branch to a backing ticket as specified in JIRA.
Create a local branch that relates the associated JIRA issue with the branch. Such an example would be:
git checkout -b nifi-359 master
This provides instant traceability to the supporting issue and provides a means of linking discussion.
Test your changes
For code changes, ensure that the full suite of tests is executed via
mvn -Pcontrib-check clean install at the root nifi folder. Please write or update unit tests to verify your changes.
Did your change introduce new dependencies? Are these dependencies licensed in a way that is compatible for inclusion under ASF 2.0? Did you update the LICENSE file?
For documentation related changes, ensure that format looks appropriate for the output in which it is rendered.
Commit your changes
List the current files that have changes
$ git status
On branch nifi-359
Changes not staged for commit:
(use "git add <file>..." to update what will be committed)
(use "git checkout -- <file>..." to discard changes in working directory)
no changes added to commit (use "git add" and/or "git commit -a")
Stage the file(s) to be committed with
$ git add nifi-docs/src/main/asciidoc/contributor-guide.adoc
$ git status
On branch nifi-359
Changes to be committed:
(use "git reset HEAD <file>..." to unstage)
In the case of multiple files, it is also possible to stage all tracked files through
git add .
Perform the commit
In the interest of providing traceability, it is helpful to lead off your commit with the associated JIRA issue number (case-sensitive, NIFI in uppercase) and a summary of the change this commit is providing. Such an example is:
$ git commit -m "NIFI-359 Adding a guide for procedure and best practices in contributing to the project."
The issue being listed first provides easy access to the supporting ticket and ensures it is not truncated from the varied means in which commits will be viewed.
Keeping your feature branch current
If you are working on a branch over an extended period of time, it helps to keep your code current with the master branch to ensure your changes are applied as anticipated and to facilitate the merging process.
This is best accomplished through the
git rebase functionality. There are many ways in which
git rebase can be utilized in this context of branching and rebasing. Typically, the command to do so is performed from your feature branch. Continuing on with the sample of NIFI-359, we will show one way of accomplishing this task.
Update your local copy of
$ git checkout master
Switched to branch 'master'
$ git fetch upstream
remote: Counting objects: 52, done.
remote: Compressing objects: 100% (11/11), done.
remote: Total 16 (delta 7), reused 0 (delta 0)
Unpacking objects: 100% (16/16), done.
a49a03d..8d745c2 master -> upstream/master
$ git merge upstream/master
nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-framework-cluster-protocol/src/main/java/org/apache/nifi/cluster/protocol/StandardDataFlow.java | 27 ++++++++++-----------------
1 file changed, 10 insertions(+), 17 deletions(-)
git rebase from your branch
$ git checkout nifi-359
Switched to branch 'nifi-359'
$ git rebase master
First, rewinding head to replay your work on top of it...
Applying: NIFI-359: Removing the output to System.out and providing some simple checks to ensure extraction of attributes is consistent with the sample file used in the test.
Supplying a contribution
There are currently two paths from which we review and accept contributions, ASF JIRA and GitHub Pull Requests (PRs), regardless of whether your contribution is source code or documentation.
Supplying a contribution through patch and JIRA issue
Assuming you are still on the branch you want to make a patch from (NIFI-359) and that you've just committed the change and it is a single commit then you can run the following to generate a patch file
`git format-patch nifi-359~1 -o </desired/path/for/patch>/nifi-359.patch`
Now you can go to JIRA for ticket NIFI-359 and select 'more -> attach files' and upload the patch file. Then select 'Submit Patch'.
TODO: Once auto-build verification comes into play this guidance will likely change.
Supplying a contribution through a pull request (PR) via GitHub
Push changes to your personal, GitHub repository remote
Typically, this remote is listed as
origin. To confirm, perform a
git remote -v from within your cloned repository directory.
$ git remote -v
origin firstname.lastname@example.org:apiri/nifi.git (push)
origin email@example.com:apiri/nifi.git (fetch)
upstream https://git-wip-us.apache.org/repos/asf/nifi.git (fetch)
Once the appropriate remote (remote name) is determined, it is possible to push the branch with your changes to GitHub through:
$ git push <remote name> <branch name>
As an example, based on the context of this guide, this would take the form of:
$ git push origin nifi-359
This will update your fork of NiFi and can be verified from your GitHub personal project page:
Opening a Pull Request (PR) to the NiFi project
From your personal fork, a Pull Request can be opened simply by selecting the Pull Request link highlighted below.
This will allow specification of the your branch which has the changes, and will open a PR for review by the committers of the project.
Code Review Process
Apache NIFI has a Review-Then-Commit (RTC) philosophy for handling all contributions. Reviewers first ensure that the code applies and builds appropriately to the build, passes the code standards as established by the Maven profile "contrib-check." From here, code is evaluated to ensure best practices within the NiFi framework are applied and, where applicable, that the user experience of interfacing with the contribution is consistent and any changes are backwards compatible. This process may be iterative but works toward a final product that is then merged into the codebase.
While only committers can actively promote contributions into the repository, feedback on issues, regardless of committer status, is appreciated and valued in the review process.
If you are interested in facilitating the review process, a listing of all code contributions with a patch are available via a JIRA filter, NIFI Patch Available.
A view of the filter is shown below:
|NIFI-3972||Controller Service failing to enabled because the service it depends on is not fully enabled on nifi restart||Mark Payne||Mark Payne||Patch Available||Unresolved||May 24, 2017||May 24, 2017|
|NIFI-3960||ExtractGrok - Include exception message when compile fails||Pierre Villard||Pierre Villard||Patch Available||Unresolved||May 23, 2017||May 23, 2017|
|NIFI-3958||Avro decimal logical type fail if database returns Zero precision||Koji Kawamura||Koji Kawamura||Patch Available||Unresolved||May 23, 2017||May 24, 2017|
|NIFI-3862||ListenHTTPServlet should set the issuerDN as well||Unassigned||Vincent Russell||Patch Available||Unresolved||May 10, 2017||May 15, 2017|
|NIFI-3859||Provide filtering options in S2SProvenanceReportingTask||Pierre Villard||Pierre Villard||Patch Available||Unresolved||May 09, 2017||May 09, 2017|
|NIFI-3858||PostHTTP support for custom headers||Unassigned||Tim Reardon||Patch Available||Unresolved||May 09, 2017||May 10, 2017|
|NIFI-3809||S2S Reporting tasks should provide the option to choose transport protocol||Pierre Villard||Pierre Villard||Patch Available||Unresolved||May 04, 2017||May 24, 2017|
|NIFI-3799||Document and / or visually show if a procesor accepts "input" connection||Pierre Villard||Juan C. Sequeiros||Patch Available||Unresolved||May 04, 2017||May 24, 2017|
|NIFI-3791||SiteToSiteStatusReportingTask - include back pressure data for connections||Pierre Villard||Pierre Villard||Patch Available||Unresolved||May 03, 2017||May 04, 2017|
|NIFI-3719||Timezone error in 5-minute statistics processing time||Unassigned||Michael Hopton||Patch Available||Unresolved||Apr 20, 2017||May 05, 2017|
|NIFI-3716||Utility to calculate MAX storage required for BackPressure on a Node||Eric Ulicny||Joseph Niemiec||Patch Available||Unresolved||Apr 19, 2017||May 12, 2017|
|NIFI-3709||Export NiFi flow dataset lineage to Apache Atlas||Koji Kawamura||Koji Kawamura||Patch Available||Unresolved||Apr 14, 2017||Apr 25, 2017|
|NIFI-3688||Create extended groovy scripting processor||Unassigned||Dmitry Lukyanov||Patch Available||Unresolved||Apr 10, 2017||May 19, 2017|
|NIFI-3640||GetEventHub should not assume domain names||Joseph Niemiec||Joseph Niemiec||Patch Available||Unresolved||Mar 23, 2017||Mar 23, 2017|
|NIFI-3625||Add JSON support to PutHiveStreaming||Unassigned||Ryan Persaud||Patch Available||Unresolved||Mar 20, 2017||May 24, 2017|
|NIFI-3583||PutFile should attempt to replace files atomically||Gray Gwizdz||Eugene Hart||Patch Available||Unresolved||Mar 09, 2017||Mar 24, 2017|
|NIFI-3568||Default thread pool that is created for cluster request replication is not sufficient||Mark Payne||Mark Payne||Patch Available||Unresolved||Mar 08, 2017||May 24, 2017|
|NIFI-3439||Making password property in HiveConnectionPool a hidden show.||Scott Aslan||Ramakrishnan V||Patch Available||Unresolved||Feb 04, 2017||Apr 16, 2017|
|NIFI-3425||Cache prepared statements in PutCassandraQL||Unassigned||Matt Burgess||Patch Available||Unresolved||Feb 01, 2017||Feb 15, 2017|
|NIFI-3422||Run Once Scheduling||Unassigned||Nazario||Patch Available||Unresolved||Jan 31, 2017||Mar 28, 2017|
Additional notes on code contributions
Rebasing and Squashing while under review
Although you may be asked to rebase or squash your contribution as part of the review process, don't feel the need to do so speculatively. The committer working on merging the contribution may prefer to do these types of operations as part of the merge process, and the history of your patch or pull request may aid in the review process.
Steps to merge/close pull requests with two main branches
As NiFi now has a 1.0 (master) and 0.x (support) branch, pull requests (PR) must be applied to both. Here is a step-by-step guide for committers to ensure this occurs for all PRs.
- Check out the latest master
$ git checkout master
- $ git pull upstream master
- Check out the PR (example #327). This will be in
detached-HEADstate. (Note: You may need to edit the
.git/configfile to add the
$ git checkout github/pr/327
- Create a branch for the PR
- $ git checkout -b pr327
- Apply the changes and sign off. This could be through a
$ git commit --amend -s
- Edit the commit file to contain "This closes #327. "
$ git log
- Copy commit id of last commit
- Switch back to the master branch
$ git checkout master
- Merge the changes. You can use
$ git cherry-pick <commit id>
- (Optional) Ensure the commit was applied successfully
$ git log
- Push to the Apache repository (master branch)
$ git push apache master
- Switch to the support branch
$ git checkout -t upstream/0.x
- (Optional) Check the status of the branch
$ git log
- Apply the changes from the PR branch
$ git cherry-pick <commit id>
- Push to the Apache repository (support branch)
$ git push apache 0.x
To ensure you are able to pull the PR directly, add the following lines to your
url = firstname.lastname@example.org:apache/nifi.git
fetch = +refs/heads/*:refs/remotes/github/*
fetch = +refs/pull/*/head:refs/remotes/github/pr/*
TODO: Provide code formatters for the common IDEs
IntelliJ IDEA Users
nifi-checkstyle.xml is a Checkstyle configuration file created by extracting
Steps for IntelliJ users:
- Download Checkstyle-IDEA plugin
- Install plugin by loading the downloaded zip from:
Install plugin from disk...
- After restarting IntelliJ, configure Checkstyle plugin to use NiFi Checkstyle configuration file from:
nifi-checkstyle.xmlin Configuration File and activate it
You can now see Checkstyle violations in the editor in real-time.
Code formatter rules that adhere to our checkstyle rules can be found here.
Consider installing these templates that help generate common Apache NiFi code snippets. TODO: provide link
The developer mailing list (email@example.com) is monitored pretty closely, and we tend to respond quickly. If you have a question, don't hesitate to shoot us an e-mail - we're here to help! Unfortunately, though, e-mails can get lost in the shuffle, so if you do send an e-mail and don't get a response within a day or two, it's our fault - don't worry about bothering us. Just ping the mailing list again.