guide.md

Developer guide

This guide details what you'll need to contribute to Materialize.

Materialize consists of several services written in Rust that are orchestrated by Kubernetes. Supporting build and test tools are written in a combination of Rust, Python, and Bash. Tests often use Docker Compose rather than Kubernetes to orchestrate interactions with other systems, like Apache Kafka.

Install build and test dependencies

C components

Materialize depends on several components that are written in C and C++, so you'll need a working C and C++ toolchain. You'll also need to install:

• The CMake build system
• libclang
• PostgreSQL

On macOS, if you install Homebrew, you'll be guided through the process of installing Apple's developer tools, which includes a C compiler and libclang. Then it's a cinch to install CMake and PostgreSQL.

brew install cmake postgresql

On Debian-based Linux variants, it's even easier:

sudo apt update
sudo apt install build-essential cmake postgresql-client libclang-dev

On other platforms, you'll have to figure out how to get these tools yourself.

Rust

Install Rust via rustup:

curl https://sh.rustup.rs -sSf | sh

We recommend that you do not install Rust via your system's package manager. We closely track the most recent version of Rust. The version of Rust in your package manager is likely too old to build Materialize.

CockroachDB

Running Materialize locally requires a running CockroachDB server.

On macOS, when using Homebrew, CockroachDB can be installed and started via:

brew install materializeinc/cockroach/cockroach
brew services start cockroach

(We recommend use of our forked Homebrew tap because it runs CockroachDB using an in-memory store, which avoids slow filesystem operations on macOS.)

On Linux, we recommend using Docker:

docker run --name=cockroach -d -p 26257:26257 -p 26258:8080 cockroachdb/cockroach:v22.2.0 start-single-node --insecure

If you can successfully connect to CockroachDB with either psql postgres://root@localhost:26257 or cockroach sql --insecure, you're all set.

Confluent Platform

The Confluent Platform bundles Apache ZooKeeper and Apache Kafka with several non-free Confluent tools, like the Confluent Schema Registry and Control Center. For local development, the Confluent CLI allows easy management of these services.

Confluent Platform is not required for changes that don't need Kafka integration. If your changes don't affect integration with external systems and can be fully exercised by SQL logic tests, we recommend not installing the Confluent Platform, as it is a rather heavy dependency. Most Materialize employees, or other major contributors, will probably need to run the full test suite and should therefore install the Confluent Platform.

WebAssembly / WASM

Some crates are compiled to WebAssembly and published to npm. This is accomplished through wasm-pack. Install it by running:

cargo install wasm-pack

WASM builds can then be initiated through

./bin/wasm-build <path/to/crate>

All platforms

First, install the CLI. As of early July 2022 you can run this command on macOS and Linux:

curl -sL --http1.1 https://cnfl.io/cli | sudo sh -s -- -b /usr/local/bin latest

If this no longer works, follow the instructions in the Confluent CLI documentation. Then please update this guide with the new instructions!

macOS

You will need JDK 8 or 11. The easiest way to install this is via Homebrew:

brew install --cask homebrew/cask-versions/temurin11

Then, download and extract the Confluent Platform tarball (when using bash, replace ~/.zshrc with ~/.bashrc):

INSTALL_DIR=$HOME/confluent  # You can choose somewhere else if you like.
mkdir $INSTALL_DIR
curl http://packages.confluent.io/archive/7.0/confluent-7.0.1.tar.gz | tar -xzC $INSTALL_DIR --strip-components=1
echo export CONFLUENT_HOME=$(cd $INSTALL_DIR && pwd) >> ~/.zshrc
source ~/.zshrc
confluent local services start

When using bash, note that you need to create a .bash_profile that sources .bashrc to ensure the above works with the Terminal app.

If you have multiple JDKs installed and your current JAVA_HOME points to an incompatible version, you can explicitly run confluent with JDK 8 or 11:

JAVA_HOME=$(/usr/libexec/java_home -v 1.11) confluent local services start

Linux

On Debian-based Linux variants, you can use APT to install Java and the Confluent Platform:

curl http://packages.confluent.io/deb/6.0/archive.key | sudo apt-key add -
sudo add-apt-repository "deb [arch=amd64] https://packages.confluent.io/deb/6.0 stable main"
sudo apt update
sudo apt install openjdk-11-jre-headless confluent-community-2.13
echo export CONFLUENT_HOME=/ >> ~/.bashrc
source ~/.bashrc
confluent local services start

On other Linux variants, you'll need to make your own way through Confluent's installation instructions. Note that, at the time of writing, only Java 8 and 11 are supported.

Alternatively, it is possible to get an all-in-one tarball from here. Then untar this to a location, set $CONFLUENT_HOME to this location and add $CONFLUENT_HOME/bin to your $PATH. I found this to be the most convenient way to get confluent and it also works in a distro neutral way (if you are using, Arch Linux for example).

Building Materialize

First, clone this repository:

git clone git@github.com:MaterializeInc/materialize.git

Because the MaterializeInc organization requires two-factor authentication (2FA), you'll need to clone via SSH as indicated above, or configure a personal access token for use with HTTPS.

Then you can build Materialize. Because Materialize is a collection of several Rust services that need to be built together, each service can be built individually via Cargo, but we recommend using the bin/environmentd script to drive the process:

cd materialize
bin/environmentd [--release] [<environmentd arg>...]

Running Confluent Platform

As mentioned above, Confluent Platform is only required need to test Kafka sources and sinks against a local Kafka installation. If possible, we recommend that you don't run the Confluent Platform if you don't need it, as it is very memory hungry.

If you do need the Confluent Platform running locally, execute the following commands:

confluent local services schema-registry start  # Also starts ZooKeeper and Kafka.

You can also use the included confluent CLI command to start and stop individual services. For example:

confluent local services status        # View what services are currently running.
confluent local services kafka start   # Start Kafka and any services it depends upon.
confluent local services kafka log     # View Kafka log file.

Beware that the CLI is fairly buggy, especially around service management. Putting your computer to sleep often causes the service status to get out of sync. In other words, trust the output of confluent local services <service> log and ps ... | grep over the output of confluent local services status. Still, it's reliable enough to be more convenient than managing each service manually.

When the confluent local services are running, they can be examined via a web UI which defaults to http://localhost:9021.

It might happen that the start script says that it failed to start zookeeper/kafka/schema-registry, but it actually starts them successfully, it just can't detect them for some reason. In this case, you can just run confluent local services schema-registry start 3 times, and then everything is up.

Web UI

Materialize embeds a web UI, which it serves from port 6876. If you're running Materialize locally, you can view the web UI at http://localhost:6876.

Developing the web UI can be painful, as by default the HTML, CSS, and JS source code for the UI gets baked into the binary, and so making a change requires a full rebuild of the binary.

To speed up the development cycle, you can enable the dev-web feature like so:

cd src/environmentd
bin/environmentd --features=dev-web

In this mode, every request for a static file will reload the file from disk. Changes to standalone CSS and JS files will be reflected immediately upon reload, without requiring a recompile!

Note that dev-web can only hot-reload the files in src/environmentd/src/static. The HTML templates in src/environmentd/src/templates use a compile-time templating library called askama, and so changes to those templates necessarily require a recompile.

For details about adding a new JavaScript/CSS dependency, see the comment in src/environmentd/build/npm.rs.

Testing

Materialize's testing philosophy is sufficiently complex that it warrants its own document. See Developer guide: testing.

Style

We use the following tools to perform automatic code style checks:

Tool	Use	Run locally with
Clippy	Rust semantic nits	cargo clippy
rustfmt	Rust code formatter	cargo fmt
Linter	General formatting nits	bin/lint
cargo-udeps	Check for unused Rust dependencies	bin/unused-deps

See the style guide for additional recommendations on code style.

Submitting and reviewing changes

See Developer guide: submitting and reviewing changes.

Code organization

Repository structure

This repository has the following basic structure:

• bin contains scripts for contributor use.
• ci contains configuration and scripts for CI.
• doc/developer contains documentation for Materialize contributors, including this document.
• doc/user contains the user-facing documentation, which is published to https://materialize.com/docs.
• misc contains a variety of supporting tools and projects. Some highlights:
  • misc/dbt-materialize contains the Materialize dbt adapter.
  • misc/python contains Python developer tools, like mzbuild.
  • misc/nix contains an experimental Nix configuration for developing Materialize.
  • misc/www contains the source code for https://dev.materialize.com.
• src contains the primary Rust crates that comprise Materialize.
• test contains test suites, which are described in Developer guide: testing.

Rust crate structure

We break our Rust code into crates primarily to promote organization of code by team, thereby introducing ownership and autonomy. As such, many crates are owned by a specific team (which does not preclude the existence of shared, cross-team crates).

Although the primary unit of code organization at the inter-team level is the crate, modules within a crate are also useful for code organization, especially because they are the level at which pub visibility operates.

We make a best-effort attempt to document the ownership of the Rust code in this repository using GitHub's CODEOWNERS file.

You can create and view a relationship diagram of our crates by running the following command (this will require graphviz):

bin/crate-diagram

It is possible to view transitive dependencies of a select subset of roots by specifying the --roots flag with a comma separated list of crates:

bin/crate-diagram --roots mz-sql,mz-dataflow

workspace-hack

The workspace-hack crate speeds up rebuilds by ensuring that all crates use the same features of all transitive dependencies in the graph. This prevents Cargo from recompiling huge chunks of the dependency graph when you move between crates in the workspace. For details, see the hakari documentation.

If you add or remove dependencies on crates, you will likely need to regenerate the workspace-hack crate. You can do this by running:

cargo install --locked cargo-hakari
cargo hakari generate
cargo hakari manage-deps

CI will enforce that the workspace-hack crate is kept up to date.

Other repositories

Where possible, we prefer to keep things in the main repository (a "monorepo" approach). There are a few exceptions:

• demos, which showcases several use cases for Materialize
• rust-dec, libdecnumber bindings for Rust
• materialize-dbt-utils, data build tool (dbt) utilities for Materialize
• Several custom Pulumi providers

Don't add to this list without good reason! Separate repositories are acceptable for:

• Rapid iteration on new Materialize plugins or integrations, where the CI time or code quality requirements in the main repository would be burdensome. When the code is more stable, the repository should be integrated into the main Materialize repository.

• External requirements that require a separate repository. For example, Pulumi providers are conventionally developed each in their own repository. Similarly, materialize-dbt-utils can only appear on dbt hub if it is developed in a standalone repository.

• Stable foundational components where community contribution is desirable. For example, rust-dec is a very small package, and asking contributors to clone the entire Materialize repository would be a large barrier to entry. Changes to Materialize very rarely require changes in rust-dec, so maintaining the two separately does not introduce much overhead.

Developer tools

Editors and IDEs

In principle, any text editor can be used to edit Rust code.

By default, we recommend that developers without a strong preference of editor use Visual Studio Code with the Rust-Analyzer plugin. This is the most mainstream setup for developing Materialize, and the one for which you are the most likely to be able to get help if something goes wrong. It's important to note that you should not install the "Rust" plugin, as it is known to conflict with Rust-Analyzer; the latter has far more advanced code navigation features and is the de-facto standard for developing Rust. If you use Rust-Analyzer, you may wish to change the target directory so it does not conflict with other cargo commands. You can do this by adding to the cargo check extra args "--target-dir" and "$NEWTARGET".

Visual Studio Code also works well for editing Python; to work on the Python code in the Materialize repository, install the official Python extension from Microsoft and add the following to your settings.json.

{
  "python.linting.mypyEnabled": true,
  "python.analysis.extraPaths": [
      "misc/python"
  ],
  "python.defaultInterpreterPath": "misc/python/venv/bin/python"
}

If you prefer to use another editor, such as Vim or Emacs, we recommend that you install an LSP plugin with Rust-Analyzer. How to do so is beyond the scope of this document; if you have any issues, ask in one of the engineering channels on Slack.

If you are using Rust-Analyzer, you should configure it to conform to our style guide by setting the following options:

• imports.granularity.group = module
• imports.prefix = crate

Besides Rust-Analyzer, the only other known tool with good code navigation features is CLion along with its Rust plugin. This is a good choice for developers who prefer the JetBrains ecosystem, but we no longer recommend it by default, since Rust-Analyzer has long since caught up to it in maturity. If you are a Materialize employee, ask Nikhil Benesch on Slack for access to our corporate JetBrains license. If you're not yet sure you want to use CLion, you can use the 30-day free trial.

Editor add-ons

A few editor-specific add-ons and configurations have been authored to improve the editing of Materialize-specific code. Check misc/editor for add-ons that may be relevant for your editor of choice.

Debugging

The standard debuggers for Rust code are rust-lldb on macOS, and rust-gdb on GNU/Linux. (It is also possible to run rust-lldb on GNU/Linux if necessary for whatever reason). These are wrappers around lldb and gdb, respectively, that endow them with slightly improved capabilities for pretty-printing Rust data structures. Visual Studio Code users may want to try the CodeLLDB plugin.

Unfortunately, you will soon find that these programs work less well than the equivalent tools for some other mainstream programming languages. In particular, inspecting complex data structures is often tedious and difficult. For this reason, most developers routinely use println! statements for debugging, in addition to (or instead of) these standard debuggers.

Automatic style checks

To ensure each code change passes all style nits before pushing to GitHub, symlink pre-push into your local git hooks:

ln -s ../../misc/githooks/pre-push .git/hooks/pre-push

Shell completion

Some Materialize scripts have shell completion, and the latest versions of the completions files are checked in to misc/completions. The contents of this directory can be sourced into your shell, and will stay updated as any changes are made.

To add the completions to bash, add the following to your ~/.bashrc:

source /path/to/materialize/misc/completions/bash/*

For zsh, add the follow to your ~/.zshrc:

source /path/to/materialize/misc/completions/zsh/*