Contributing to Kong 🐵

Hello, and welcome! Whether you are looking for help, trying to report a bug, thinking about getting involved in the project, or about to submit a patch, this document is for you! It intends to be both an entry point for newcomers to the community (with various technical backgrounds), and a guide/reference for contributors and maintainers.

Please have a look at our Community Pledge to understand how we work with our open-source contributors!

Consult the Table of Contents below, and jump to the desired section.

Table of Contents

Contributing to Kong 🐵

Where to seek for help?

Enterprise Edition

If you are a Kong Enterprise customer, you may contact the Enterprise Support channels by opening an Enterprise support ticket on https://support.konghq.com.

If you are experiencing a P1 issue, please call the 24/7 Enterprise Support phone line for immediate assistance, as published in the Customer Success Reference Guide.

If you are interested in becoming a Kong Enterprise customer, please visit https://konghq.com/kong-enterprise-edition/ or contact us at sales@konghq.com.

Community Edition

For questions about the use of the Community Edition, please use GitHub Discussions. You can also join our Community Slack for real-time conversations around Kong Gateway.

Please avoid opening GitHub issues for general questions or help, as those should be reserved for actual bug reports. The Kong community is welcoming and more than willing to assist you on those channels!

Our public forum, Kong Nation is great for asking questions, giving advice, and staying up-to-date with the latest announcements.

Where to report bugs?

Feel free to submit an issue on the GitHub repository, we would be grateful to hear about it! Please make sure that you respect the GitHub issue template, and include:

A summary of the issue
A list of steps to help reproduce the issue
The version of Kong that you encountered the issue with
Your Kong configuration, or the parts that are relevant to your issue

If you wish, you are more than welcome to propose a patch to fix the issue! See the Submit a patch section for more information on how to best do so.

Where to submit feature requests?

You can submit an issue for feature requests. Please make sure to add as much detail as you can when doing so.

You are also welcome to propose patches adding new features. See the section on Submitting a patch for details.

Contributing

In addition to code enhancements and bug fixes, you can contribute by

Reporting a bug (see the report bugs section)
Helping other members of the community on the support channels
Fixing a typo in the code
Fixing a typo in the documentation at https://docs.konghq.com (see the documentation contribution section)
Providing your feedback on the proposed features and designs
Reviewing Pull Requests

If you wish to contribute code (features or bug fixes), see the Submitting a patch section.

Improving the documentation

The documentation hosted at https://docs.konghq.com is open source and built with Jekyll. You are very welcome to propose changes to it (correct typos, add examples or clarifications...) and contribute to the Kong Hub!

The repository is also hosted on GitHub at: https://github.com/Kong/docs.konghq.com/

Proposing a new plugin

We do not generally accept new plugins into this repository. The plugins that are currently part of it form the foundational set of plugins which is available to all installations of Kong Gateway. Specialized functionality should be implemented in plugins residing in separate repository.

If you are interested in writing a new plugin for your own needs, you should begin by reading the Plugin Development Guide.

If you already wrote a plugin, and are thinking about making it available to the community, we strongly encourage you to host it on a publicly available repository (like GitHub), and distribute it via LuaRocks. A good resource on how to do so is the Distribution Section of the Plugin Development Guide.

To give visibility to your plugin, we advise that you:

Add your plugin to the Kong Hub
Create a post in the Announcements category of Kong Nation

Submitting a patch

Feel free to contribute fixes or minor features by opening a Pull Request. Small contributions are more likely to be merged quicker than changes which require a lot of time to review. If you are planning to develop a larger feature, please talk to us first in the GitHub Discussions section!

When contributing, please follow the guidelines provided in this document. They will cover topics such as the different Git branches we use, the commit message format to use, or the appropriate code style.

Once you have read them, and you feel that you are ready to submit your Pull Request, be sure to verify a few things:

Your commit history is clean: changes are atomic and the git message format was respected
Rebase your work on top of the base branch (seek help online on how to use git rebase; this is important to ensure your commit history is clean and linear)
The static linting is succeeding: run make lint, or luacheck . (see the development documentation for additional details)
The tests are passing: run make test, make test-all, or whichever is appropriate for your change
Do not update CHANGELOG.md inside your Pull Request. This file is automatically regenerated and maintained during the release process.

If the above guidelines are respected, your Pull Request has all its chances to be considered and will be reviewed by a maintainer.

If you are asked to update your patch by a reviewer, please do so! Remember: You are responsible for pushing your patch forward. If you contributed it, you are probably the one in need of it. You must be ready to apply changes to it if necessary.

If your Pull Request was accepted and fixes a bug, adds functionality, or makes it significantly easier to use or understand Kong, congratulations! You are now an official contributor to Kong. Get in touch with us to receive your very own Contributor Badge!

Your change will be included in the subsequent release and its changelog, and we will not forget to include your name if you are an external contributor. 😉

Git branches

If you have write access to the GitHub repository, please follow the following naming scheme when pushing your branch(es):

feat/foo-bar for new features
fix/foo-bar for bug fixes
tests/foo-bar when the change concerns only the test suite
refactor/foo-bar when refactoring code without any behavior change
style/foo-bar when addressing some style issue
docs/foo-bar for updates to the README.md, this file, or similar documents
chore/foo-bar when the change does not concern the functional source
perf/foo-bar for performance improvements

Commit atomicity

When submitting patches, it is important that you organize your commits in logical units of work. You are free to propose a patch with one or many commits, as long as their atomicity is respected. This means that no unrelated changes should be included in a commit.

For example: you are writing a patch to fix a bug, but in your endeavour, you spot another bug. Do not fix both bugs in the same commit! Finish your work on the initial bug, propose your patch, and come back to the second bug later on. This is also valid for unrelated style fixes, refactors, etc...

You should use your best judgment when facing such decisions. A good approach for this is to put yourself in the shoes of the person who will review your patch: will they understand your changes and reasoning just by reading your commit history? Will they find unrelated changes in a particular commit? They shouldn't!

Writing meaningful commit messages that follow our commit message format will also help you respect this mantra (see the below section).

Commit message format

To maintain a healthy Git history, we ask of you that you write your commit messages as follows:

The tense of your message must be present
Your message must be prefixed by a type, and a scope
The header of your message should not be longer than 50 characters
A blank line should be included between the header and the body
The body of your message should not contain lines longer than 72 characters

We strive to adapt the conventional-commits format.

Here is a template of what your commit message should look like:

<type>(<scope>): <subject>
<BLANK LINE>
<body>
<BLANK LINE>
<footer>

Type

The type of your commit indicates what type of change this commit is about. The accepted types are:

feat: A new feature
fix: A bug fix
hotfix: An urgent bug fix during a release process
tests: A change that is purely related to the test suite only (fixing a test, adding a test, improving its reliability, etc...)
docs: Changes to the README.md, this file, or other such documents
style: Changes that do not affect the meaning of the code (white-space trimming, formatting, etc...)
perf: A code change that significantly improves performance
refactor: A code change that neither fixes a bug nor adds a feature, and is too big to be considered just perf
chore: Maintenance changes related to code cleaning that isn't considered part of a refactor, build process updates, dependency bumps, or auxiliary tools and libraries updates (LuaRocks, GitHub Actions, etc...).

Scope

The scope is the part of the codebase that is affected by your change. Choosing it is at your discretion, but here are some of the most frequent ones:

proxy: A change that affects the proxying of requests
router: A change that affects the router, which matches a request to the desired configured API
admin: A change to the Admin API
balancer: Changes related to the internal Load Balancer
core: Changes affecting a large part of the core, and touching many parts such as proxy, balancer, dns
dns: Changes related to internal DNS resolution
dao: A change related to the DAO, the interface to the datastores
cli: Changes to the CLI
cache: Changes to the configuration entities caching (datastore entities)
deps: When updating dependencies (to be used with the chore prefix)
conf: Configuration-related changes (new values, improvements...)
<plugin-name>: This could be basic-auth, or ldap for example
*: When the change affects too many parts of the codebase at once (this should be rare and avoided)

Subject

Your subject should contain a succinct description of the change. It should be written so that:

It uses the present, imperative tense: "fix typo", and not "fixed" or "fixes"
It is not capitalized: "fix typo", and not "Fix typo"
It does not include a period. 😄

Body

The body of your commit message should contain a detailed description of your changes. Ideally, if the change is significant, you should explain its motivation and the chosen implementation, and justify it.

As previously mentioned, lines in the commit messages should not exceed 72 characters.

Footer

The footer is the ideal place to link to related material about the change: related GitHub issues, Pull Requests, fixed bug reports, etc...

Examples

Here are a few examples of good commit messages to take inspiration from:

fix(admin): send HTTP 405 on unsupported method

The appropriate status code when the request method is not supported
on an endpoint is 405. We previously used to send HTTP 404, which
is not appropriate. This updates the Admin API helpers to properly
return 405 on such user errors.

* return 405 when the method is not supported in the Admin API helpers
* add a new test case in the Admin API test suite

Fix #678

Or:

tests(proxy): add a new test case for URI encoding

When proxying upstream, the URI sent by Kong should be the one
received from the client, even if it was percent-encoded.

This adds a new test case which was missing, to ensure it is
the case.

Static linting

As mentioned in the guidelines to submit a patch, the linter must succeed. We use Luacheck to statically lint our Lua code. You can lint the code like so:

$ make lint

Or:

$ luacheck .

Writing tests

We use busted to write our tests. Your patch must include the related test updates or additions, in the appropriate test suite.

spec/01-unit gathers our unit tests (to test a given Lua module or function)
spec/02-integration contains tests that start Kong (connected to a running database), execute Admin API and proxy requests against it, and verify the output
spec/03-plugins contains tests (both unit and integration) for the bundled plugins (those plugins still live in the core repository as of now, but will eventually be externalized.)

A few guidelines when writing tests:

Make sure to use appropriate describe and it blocks, so it's obvious what is being tested exactly
Ensure the atomicity of your tests: no test should be asserting two unrelated behaviors at the same time
Run tests related to the datastore against all supported databases

And a few recommendations, when asserting types:

-- bad
assert.Nil(foo)
assert.True(bar)

-- good
assert.is_nil(foo)
assert.is_true(bar)

Comparing tables:

-- bad (most of the time)
assert.equal(t1, t2)

-- good
assert.same(t1, t2)

Writing changelog

Please follow the guidelines in Changelog Readme on how to write a changelog for your change.

Writing performant code

We write code for the LuaJIT interpreter, not Lua-PUC. As such, you should follow the LuaJIT best practices:

Do not instantiate global variables
Consult the LuaJIT wiki
Follow the Performance Guide recommendations
Do not use NYI functions on hot code paths
Prefer using the FFI over traditional bindings via the Lua C API

Avoid table rehash by pre-allocating the slots of your tables when possible

-- bad
local t = {}
for i = 1, 100 do
  t[i] = i
end

-- good
local new_tab = require "table.new"
local t = new_tab(100, 0)
for i = 1, 100 do
  t[i] = i
end

Cache the globals used by your hot code paths, the cached name should be the original name replaced . by _

-- bad
for i = 1, 100 do
  t[i] = math.random()
end

-- good
local math_random = math.random
for i = 1, 100 do
  t[i] = math_random()
end

For OpenResty built-in APIs, we may drop ngx. in the localized version

local req_get_post_args = ngx.req.get_post_args

Non-hot paths are localization-optional

if err then
  ngx.log(ngx.ERR, ...) -- this is fine as the error condition is not on the hot path
end

Cache the length and indices of your tables to avoid unnecessary CPU cycles

-- bad
for i = 1, 100 do
  t[#t + 1] = other_tab[#other_tab]
end

-- good
local n = 0
local n_other_tab = #other_tab
for i = 1, 100 do
  n = n + 1
  t[n] = other_tab[n_other_tab]
end

And finally, most importantly: use your best judgment to design an efficient algorithm. Doing so will always be more performant than a poorly designed algorithm, even following all the performance tricks of the language you are using. 😄

Adding Changelog

Please follow the changelog instructions to create the appropriate changelog file for your Pull Request.

Contributor Badge

If your Pull Request to Kong/kong was accepted, and it fixes a bug, adds functionality, or makes it significantly easier to use or understand Kong, congratulations! You are eligible to receive the very special digital Contributor Badge! Go ahead and fill out the Contributors Submissions form.

Proudly display your Badge and show it to us by tagging @thekonginc on Twitter!

Badges expire after 1 year, at which point you may submit a new contribution to renew the badge.

Code style

In order to ensure a healthy and consistent codebase, we ask of you that you respect the adopted code style. This section contains a non-exhaustive list of preferred styles for writing Lua. It is opinionated, but follows the code styles of OpenResty and, by association, Nginx. OpenResty or Nginx contributors should find themselves at ease when contributing to Kong.

No line should be longer than 80 characters
Indentation should consist of 2 spaces

When you are unsure about the style to adopt, please browse other parts of the codebase to find a similar case, and stay consistent with it.

You might also notice places in the codebase where the described style is not respected. This is due to legacy code. Contributions to update the code to the recommended style are welcome!

Table of Contents - Code style

Modules
Variables
Tables
Strings
Functions
Conditional expressions

Modules

When writing a module (a Lua file), separate logical blocks of code with two blank lines:

local foo = require "kong.foo"


local _M = {}


function _M.bar()
  -- do thing...
end


function _M.baz()
  -- do thing...
end


return _M

Back to code style TOC

Variables

When naming a variable or function, do use snake_case:

-- bad
local myString = "hello world"

-- good
local my_string = "hello world"

When assigning a constant variable, do give it an uppercase name:

-- bad
local max_len = 100

-- good
local MAX_LEN = 100

Back to code style TOC

Tables

Use the constructor syntax, and do include a trailing comma:

-- bad
local t = {}
t.foo = "hello"
t.bar = "world"

-- good
local t = {
  foo = "hello",
  bar = "world", -- note the trailing comma
}

On single-line constructors, do include spaces around curly-braces and assignments:

-- bad
local t = {foo="hello",bar="world"}

-- good
local t = { foo = "hello", bar = "world" }

Prefer ipairs() to for loop when iterating an array, which gives us more readability:

-- bad
for i = 1, #t do
  ...
end

-- good
for _, v in ipairs(t) do
  ...
end

Back to code style TOC

Strings

Do favor the use of double quotes in all Lua code (plain files and *_by_lua_block directives):

-- bad
local str = 'hello'

-- good
local str = "hello"

If a string contains double quotes, do favor long bracket strings:

-- bad
local str = "message: \"hello\""

-- good
local str = [[message: "hello"]]

When using the concatenation operator, do insert spaces around it:

-- bad
local str = "hello ".."world"

-- good
local str = "hello " .. "world"

If a string is too long, do break it into multiple lines, and join them with the concatenation operator:

-- bad
local str = "It is a very very very long string, that should be broken into multiple lines."

-- good
local str = "It is a very very very long string, " ..
            "that should be broken into multiple lines."

Back to code style TOC

Functions

Prefer the function syntax over variable syntax:

-- bad
local foo = function()

end

-- good
local function foo()

end

Perform validation early and return as early as possible:

-- bad
local function check_name(name)
  local valid = #name > 3
  valid = valid and #name < 30

  -- other validations

  return valid
end

-- good
local function check_name(name)
  if #name <= 3 or #name >= 30 then
    return false
  end

  -- other validations

  return true
end

Follow the return values conventions: Lua supports multiple return values, and by convention, handles recoverable errors by returning nil plus a string describing the error:

-- bad
local function check()
  local ok, err = do_thing()
  if not ok then
    return false, { message = err }
  end

  return true
end

-- good
local function check()
  local ok, err = do_thing()
  if not ok then
    return nil, "could not do thing: " .. err
  end

  return true
end

When a function call makes a line go over 80 characters, do align the overflowing arguments to the first one:

-- bad
local str = string.format("SELECT * FROM users WHERE first_name = '%s'", first_name)

-- good
local str = string.format("SELECT * FROM users WHERE first_name = '%s'",
                          first_name)

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Conditional expressions

Avoid writing 1-line conditions, do indent the child branch:

-- bad
if err then return nil, err end

-- good
if err then
  return nil, err
end

When testing the assignment of a value, do use shortcuts, unless you care about the difference between nil and false:

-- bad
if str ~= nil then

end

-- good
if str then

end

When creating multiple branches that span multiple lines, do include a blank line above the elseif and else statements:

-- bad
if foo then
  do_stuff()
  keep_doing_stuff()
elseif bar then
  do_other_stuff()
  keep_doing_other_stuff()
else
  error()
end

-- good
if thing then
  do_stuff()
  keep_doing_stuff()

elseif bar then
  do_other_stuff()
  keep_doing_other_stuff()

else
  error()
end

For one-line blocks, blank lines are not necessary:

--- good
if foo then
  do_stuff()
else
  error("failed!")
end

Note in the correct "long" example that if some branches are long, then all branches are created with the preceding blank line (including the one-liner else case).

When a branch returns, do not create subsequent branches, but write the rest of your logic on the parent branch:

-- bad
if not str then
  return nil, "bad value"
else
  do_thing(str)
end

-- good
if not str then
  return nil, "bad value"
end

do_thing(str)

When assigning a value or returning from a function, do use ternaries if it makes the code more readable:

-- bad
local foo
if bar then
  foo = "hello"

else
  foo = "world"
end

-- good
local foo = bar and "hello" or "world"

When an expression makes a line longer than 80 characters, do align the expression on the following lines:

-- bad
if thing_one < 1 and long_and_complicated_function(arg1, arg2) < 10 or thing_two > 10 then

end

-- good
if thing_one < 1 and long_and_complicated_function(arg1, arg2) < 10
   or thing_two > 10
then

end

When invoking ngx.log() with some variable as input, prefer vararg-style calls rather than using the string concatenation operator (..):

-- bad
ngx.log(ngx.DEBUG, "if `my_var` is nil, this code throws an exception: " .. my_var)

-- good
ngx.log(ngx.DEBUG, "if `my_var` is nil, this code is fine: ", my_var)

Back to code style TOC