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Contributing to QuestDB

Raise an Issue

Raising issues is welcome. We aim to respond quickly and thoughtfully. This is a good place to start before deep diving into the code base.

Contribute a PR

Requirements

  • Operating system - x86-64: Windows, Linux, FreeBSD and OSX
  • Java 11 64-bit
  • Maven 3 (from your package manager on Linux / OSX (Homebrew) or from the jar for any OS)
  • Node.js 12 / npm 6 (to manage your Node.js versions we recommend nvm for OSX/Linux/windows WSL, and nvm-windows for Windows) - OPTIONAL
  • C-compiler, CMake - to contribute to C libraries - OPTIONAL

Repository overview

Compiled binaries (for C libraries and Windows service wrapper) are committed to git to make build of development process Java-centric and simplified.

Local setup

Setup Java and JAVA_HOME

JAVAHOME is required by Maven. It is possible to have multiple version of Java on the same platform. Please set up JAVA_HOME to point to Java 11. Other versions of Java may not work. If you are new to Java please check that JAVA_HOME is pointing to the root of Java directory: C:\Users\me\dev\jdk-11.0.8 and _not C:\Users\me\dev\jdk-11.0.8\bin\java.

Linux/OSX

export JAVA_HOME="/path/to/java/"

Windows

set JAVA_HOME="c:\path\to\java directory"

Compiling Java and frontend code

Compiling the database + the web console can be done with:

mvn clean package -DskipTests -P build-web-console

You can then run QuestDB with:

java -p core/target/questdb-<version>-SNAPSHOT.jar -m io.questdb/io.questdb.ServerMain -d <root_dir>

The web console will available at localhost:9000.

Compiling C-libraries

C-libraries will have to be compiled for each platform separately. Cmake will also need JAVA_HOME to be set. The following commands will compile on Linux/OSX.

cmake .
make

For C/С++ development we use CLion. This IDE "understands" cmake files and makes compilation easier.

The build will copy artifacts as follows:

core/src/main/c -> core/src/main/resources/io/questdb/bin

Local setup for frontend development

Development server

This is useful when you want to work on the web console without having to rebuild the artifacts and restart QuestDB. Instead, we use webpack-dev-server:

  1. Make sure QuestDB is running
  2. cd ui/
  3. Install the dependencies with npm install
  4. Start the development web server with npm start

The web console should now be accessible at localhost:9999

Development server running on port 9999 will monitor for web console file changes and will rebuild/deploy on the fly. The web console front end will be connecting to QuestDB REST API on port 9000. Keep QuestDB server running.

Building web console bundle into questdb.jar

Run the command:

mvn clean package -DskipTests -P build-web-console

The build will copy artifacts as follows:

ui -> core/src/main/resources/io/questdb/site/public.zip

Testing

We have a lot of unit tests, most of which are of "integration" type, e.g. test starts a server, interacts with it and asserts the outcome. We expect all contributors to submit PRs with tests. Please reach out to us via slack if you uncertain on how to test, or you think existing test is inadequate and should be removed.

Dependencies

QuestDB does not have dependencies. This may sound unorthodox but in reality we try not to reinvent the wheel but rather than using libraries we implement algorithms on first principles to ensure perfect fit with existing code. With that in mind we expect contributions that do not add third-party dependencies.

Allocations, "new" operator and garbage collection

QuestDB is zero-GC along data pipelines. We expect contributions not to allocate if possible. That said we would like to help you to contribute zero-GC code, do not hesitate to reach out!

Committing

We use Conventional commits to auto-generate release notes. We require all commit comments to conform. To that end, commits have to be granular enough to be successfully described using this method.

Squashing commits

When submitting a pull request to QuestDB, we ask that you squash your commits before we merge.

Some applications that interact with git repos will provide a user interface for squashing. Refer to your application's document for more information.

If you're familiar with the terminal, you can do the following:

  • Make sure your branch is up to date with the master branch.
  • Run git rebase -i master.
  • You should see a list of commits, each commit starting with the word "pick".
  • Make sure the first commit says "pick" and change the rest from "pick" to "squash". -- This will squash each commit into the previous commit, which will continue until every commit is squashed into the first commit.
  • Save and close the editor.
  • It will give you the opportunity to change the commit message.
  • Save and close the editor again.
  • Then you have to force push the final, squashed commit: git push --force-with-lease origin.

Squashing commits can be a tricky process but once you figure it out, it is really helpful and keeps our repository concise and clean.

FAQ

Why does the server work, but the UI returns a 404 on localhost:9000?

This means that the web console artifacts are not present in core/src/main/resources/io/questdb/site/public.zip. To fix this, you can simply run:

mvn clean package -DskipTests -P build-web-console

How can I easily manage the Node.js installation?

You can use nvm for OSX/Linux/windows WSL, and nvm-windows for Windows. To have multiple active versions.

Otherwise, you can use the dedicated maven profile to build the code:

mvn clean package -DskipTests -P build-web-console,build-binaries

That way, maven will install node on the fly in ui/node so you don't have to install it locally.

Why do some tests fail on Windows?

Some antivirus software may cause tests to fail. Typical indicators that antivirus is interfering with tests are that tests pass on CI but are failing in the following cases:

  • HTTP chunk size assertion (missing initial zeroes in e.g. IODispatcherTest)
  • Test timeout
  • JVM crash

In case of ESET products, the following steps may resolve the issue:

  • Disable "application protocol content filtering" explicitly or
  • Add 127.0.0.1 to "Excluded IP addresses" list in the advanced settings menu because disabling all top-level mechanisms doesn't turn protocol filtering off.