README.md - datafusion-ballista - Git at Google

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 # Ballista: Making DataFusion Applications Distributed

 [![Apache licensed][license-badge]][license-url]

 [license-badge]: https://img.shields.io/badge/license-Apache%20v2-blue.svg
 [license-url]: https://github.com/apache/datafusion-comet/blob/main/LICENSE.txt

 <img src="docs/source/_static/images/ballista-logo.png" width="512" alt="logo"/>

 Ballista is a distributed query execution engine that enhances [Apache DataFusion](https://github.com/apache/datafusion)
 by enabling the parallelized execution of workloads across multiple nodes in a distributed environment.

 Existing DataFusion application:

 ```rust
 use datafusion::prelude::*;

 #[tokio::main]
 async fn main() -> datafusion::error::Result<()> {
     let ctx = SessionContext::new();

     // register the table
     ctx.register_csv("example", "tests/data/example.csv", CsvReadOptions::new())
         .await?;

     // create a plan to run a SQL query
     let df = ctx
         .sql("SELECT a, MIN(b) FROM example WHERE a <= b GROUP BY a LIMIT 100")
         .await?;

     // execute and print results
     df.show().await?;
     Ok(())
 }
 ```

 can be distributed with few lines of code changed:

 > [!IMPORTANT]
 > There is a gap between DataFusion and Ballista, which may bring incompatibilities. The community is actively working
 > to close the gap

 ```rust
 use ballista::prelude::*;
 use datafusion::prelude::*;

 #[tokio::main]
 async fn main() -> datafusion::error::Result<()> {
     // create SessionContext with ballista support
     // standalone context will start all required
     // ballista infrastructure in the background as well
     let ctx = SessionContext::standalone().await?;

     // everything else remains the same

     // register the table
     ctx.register_csv("example", "tests/data/example.csv", CsvReadOptions::new())
         .await?;

     // create a plan to run a SQL query
     let df = ctx
         .sql("SELECT a, MIN(b) FROM example WHERE a <= b GROUP BY a LIMIT 100")
         .await?;

     // execute and print results
     df.show().await?;
     Ok(())
 }
 ```

 For documentation or more examples, please refer to the [Ballista User Guide][user-guide].

 ## Who is Ballista for

 Ballista serves several distinct audiences:

 - **DataFusion users going multi-node** — you already use [Apache DataFusion](https://github.com/apache/datafusion) on a single machine and have outgrown it. Ballista runs the same SQL and DataFrame workloads across a cluster with minimal code changes and the same results.
 - **Spark users wanting the same execution model** — you run Spark SQL or batch jobs and want a lighter, Rust-native alternative without relearning a new paradigm. Ballista keeps the familiar model: plans split into stages at shuffle boundaries, one task per partition, executors with vcores, and adaptive query execution (AQE).
 - **Library users building a specialized engine** — you are building a bespoke distributed query engine and want reusable scheduler, executor, and plan-serialization building blocks with extension points, instead of writing distributed execution from scratch.

 These audiences are documented in more detail, along with the guarantees each relies on, in the [User Personas](docs/source/contributors-guide/user-personas.md) guide.

 ## Architecture

 A Ballista cluster consists of one or more scheduler processes and one or more executor processes. These processes
 can be run as native binaries and are also available as Docker Images, which can be easily deployed with
 [Docker Compose](https://datafusion.apache.org/ballista/user-guide/deployment/docker-compose.html) or
 [Kubernetes](https://datafusion.apache.org/ballista/user-guide/deployment/kubernetes.html).

 The following diagram shows the interaction between clients and the scheduler for submitting jobs, and the interaction
 between the executor(s) and the scheduler for fetching tasks and reporting task status.

 ![Ballista Cluster Diagram](docs/source/contributors-guide/ballista_architecture.excalidraw.svg)

 See the [architecture guide](docs/source/contributors-guide/architecture.md) for more details.

 ## Getting Started

 The easiest way to get started is to run one of the standalone or distributed [examples](./examples/README.md). After
 that, refer to the [Getting Started Guide](ballista/client/README.md).

 ## Web Terminal User Interface (Web TUI)

 Ballista provides a browser-based Web TUI for monitoring a running cluster. It exposes the TUI views for jobs, executors, metrics, and scheduler information directly in a web browser.

 ![Ballista Web TUI](docs/source/user-guide/screenshots/tui-web-main.png)

 When the scheduler HTTP endpoint is available, opening the scheduler address in a browser, for example `http://localhost:50050`, redirects to a hosted Web TUI.

 For more information, including how to run the Web TUI locally, see the [Ballista CLI documentation](https://datafusion.apache.org/ballista/user-guide/cli.html).

 ## Cargo Features

 Ballista uses Cargo features to enable optional functionality. Below are the available features for each crate.

 ### ballista (client)

 | Feature      | Default | Description                                                    |
 | ------------ | ------- | -------------------------------------------------------------- |
 | `standalone` | Yes     | Enables standalone mode with in-process scheduler and executor |

 ### ballista-core

 | Feature                   | Default | Description                                                            |
 | ------------------------- | ------- | ---------------------------------------------------------------------- |
 | `arrow-ipc-optimizations` | Yes     | Enables Arrow IPC optimizations for better shuffle performance         |
 | `spark-compat`            | No      | Enables Spark compatibility mode via datafusion-spark                  |
 | `build-binary`            | No      | Required for building binary executables (AWS S3 support, CLI parsing) |
 | `force_hash_collisions`   | No      | Testing-only: forces all values to hash to same value                  |

 ### ballista-scheduler

 | Feature                    | Default | Description                                      |
 | -------------------------- | ------- | ------------------------------------------------ |
 | `build-binary`             | Yes     | Builds the scheduler binary with CLI and logging |
 | `substrait`                | No      | Enables Substrait plan support                   |
 | `prometheus-metrics`       | No      | Enables Prometheus metrics collection            |
 | `graphviz-support`         | No      | Enables execution graph visualization            |
 | `spark-compat`             | No      | Enables Spark compatibility mode                 |
 | `keda-scaler`              | No      | Kubernetes Event Driven Autoscaling integration  |
 | `rest-api`                 | No      | Enables REST API endpoints                       |
 | `disable-stage-plan-cache` | No      | Disables caching of stage execution plans        |

 ### ballista-executor

 | Feature                   | Default | Description                                           |
 | ------------------------- | ------- | ----------------------------------------------------- |
 | `arrow-ipc-optimizations` | Yes     | Enables Arrow IPC optimizations                       |
 | `build-binary`            | Yes     | Builds the executor binary with CLI and logging       |
 | `mimalloc`                | Yes     | Uses mimalloc memory allocator for better performance |
 | `spark-compat`            | No      | Enables Spark compatibility mode                      |

 ### ballista-cli

 | Feature | Default | Description                                        |
 | ------- | ------- | -------------------------------------------------- |
 | `tui`   | Yes     | Enables a REST client with Terminal User Interface |

 ![TUI Jobs table](./docs/source/user-guide/screenshots/tui-jobs-table.png)

 ### Usage Examples

 ```bash
 # Build with standalone support (default)
 cargo build -p ballista

 # Build with Substrait support
 cargo build -p ballista-scheduler --features substrait

 # Build with Spark compatibility
 cargo build -p ballista-executor --features spark-compat
 ```

 ## Project Status

 Ballista supports a wide range of SQL, including CTEs, Joins, and subqueries and can execute complex queries at scale,
 but still there is a gap between DataFusion and Ballista which we want to bridge in near future.

 Refer to the [DataFusion SQL Reference](https://datafusion.apache.org/user-guide/sql/index.html) for more
 information on supported SQL.

 ## Who uses Ballista

 The following organizations use Ballista. To add yours, open a pull request.

 | Organization                                                                                                                   |                                                               |
 | ------------------------------------------------------------------------------------------------------------------------------ | ------------------------------------------------------------- |
 | <a href="https://spice.ai"><img src="docs/source/_static/images/adopters/spiceai.png" height="36" alt="Spice AI"/></a>         | [Spice AI](https://spice.ai/blog/apache-ballista-at-spice-ai) |
 | <a href="https://coralogix.com"><img src="docs/source/_static/images/adopters/coralogix.png" height="36" alt="Coralogix"/></a> | [Coralogix](https://coralogix.com/)                           |

 ## Contribution Guide

 Please see the [Contribution Guide](CONTRIBUTING.md) for information about contributing to Ballista.

 [user-guide]: https://datafusion.apache.org/ballista/
	<!---
	Licensed to the Apache Software Foundation (ASF) under one
	or more contributor license agreements. See the NOTICE file
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	regarding copyright ownership. The ASF licenses this file
	to you under the Apache License, Version 2.0 (the
	"License"); you may not use this file except in compliance
	with the License. You may obtain a copy of the License at

	http://www.apache.org/licenses/LICENSE-2.0

	Unless required by applicable law or agreed to in writing,
	software distributed under the License is distributed on an
	"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
	KIND, either express or implied. See the License for the
	specific language governing permissions and limitations
	under the License.
	-->

	# Ballista: Making DataFusion Applications Distributed

	[![Apache licensed][license-badge]][license-url]

	[license-badge]: https://img.shields.io/badge/license-Apache%20v2-blue.svg
	[license-url]: https://github.com/apache/datafusion-comet/blob/main/LICENSE.txt

	<img src="docs/source/_static/images/ballista-logo.png" width="512" alt="logo"/>

	Ballista is a distributed query execution engine that enhances [Apache DataFusion](https://github.com/apache/datafusion)
	by enabling the parallelized execution of workloads across multiple nodes in a distributed environment.

	Existing DataFusion application:

	```rust
	use datafusion::prelude::*;

	#[tokio::main]
	async fn main() -> datafusion::error::Result<()> {
	let ctx = SessionContext::new();

	// register the table
	ctx.register_csv("example", "tests/data/example.csv", CsvReadOptions::new())
	.await?;

	// create a plan to run a SQL query
	let df = ctx
	.sql("SELECT a, MIN(b) FROM example WHERE a <= b GROUP BY a LIMIT 100")
	.await?;

	// execute and print results
	df.show().await?;
	Ok(())
	}
	```

	can be distributed with few lines of code changed:

	> [!IMPORTANT]
	> There is a gap between DataFusion and Ballista, which may bring incompatibilities. The community is actively working
	> to close the gap

	```rust
	use ballista::prelude::*;
	use datafusion::prelude::*;

	#[tokio::main]
	async fn main() -> datafusion::error::Result<()> {
	// create SessionContext with ballista support
	// standalone context will start all required
	// ballista infrastructure in the background as well
	let ctx = SessionContext::standalone().await?;

	// everything else remains the same

	// register the table
	ctx.register_csv("example", "tests/data/example.csv", CsvReadOptions::new())
	.await?;

	// create a plan to run a SQL query
	let df = ctx
	.sql("SELECT a, MIN(b) FROM example WHERE a <= b GROUP BY a LIMIT 100")
	.await?;

	// execute and print results
	df.show().await?;
	Ok(())
	}
	```

	For documentation or more examples, please refer to the [Ballista User Guide][user-guide].

	## Who is Ballista for

	Ballista serves several distinct audiences:

	- DataFusion users going multi-node — you already use [Apache DataFusion](https://github.com/apache/datafusion) on a single machine and have outgrown it. Ballista runs the same SQL and DataFrame workloads across a cluster with minimal code changes and the same results.
	- Spark users wanting the same execution model — you run Spark SQL or batch jobs and want a lighter, Rust-native alternative without relearning a new paradigm. Ballista keeps the familiar model: plans split into stages at shuffle boundaries, one task per partition, executors with vcores, and adaptive query execution (AQE).
	- Library users building a specialized engine — you are building a bespoke distributed query engine and want reusable scheduler, executor, and plan-serialization building blocks with extension points, instead of writing distributed execution from scratch.

	These audiences are documented in more detail, along with the guarantees each relies on, in the [User Personas](docs/source/contributors-guide/user-personas.md) guide.

	## Architecture

	A Ballista cluster consists of one or more scheduler processes and one or more executor processes. These processes
	can be run as native binaries and are also available as Docker Images, which can be easily deployed with
	[Docker Compose](https://datafusion.apache.org/ballista/user-guide/deployment/docker-compose.html) or
	[Kubernetes](https://datafusion.apache.org/ballista/user-guide/deployment/kubernetes.html).

	The following diagram shows the interaction between clients and the scheduler for submitting jobs, and the interaction
	between the executor(s) and the scheduler for fetching tasks and reporting task status.

	![Ballista Cluster Diagram](docs/source/contributors-guide/ballista_architecture.excalidraw.svg)

	See the [architecture guide](docs/source/contributors-guide/architecture.md) for more details.

	## Getting Started

	The easiest way to get started is to run one of the standalone or distributed [examples](./examples/README.md). After
	that, refer to the [Getting Started Guide](ballista/client/README.md).

	## Web Terminal User Interface (Web TUI)

	Ballista provides a browser-based Web TUI for monitoring a running cluster. It exposes the TUI views for jobs, executors, metrics, and scheduler information directly in a web browser.

	![Ballista Web TUI](docs/source/user-guide/screenshots/tui-web-main.png)

	When the scheduler HTTP endpoint is available, opening the scheduler address in a browser, for example `http://localhost:50050`, redirects to a hosted Web TUI.

	For more information, including how to run the Web TUI locally, see the [Ballista CLI documentation](https://datafusion.apache.org/ballista/user-guide/cli.html).

	## Cargo Features

	Ballista uses Cargo features to enable optional functionality. Below are the available features for each crate.

	### ballista (client)

	\| Feature \| Default \| Description \|
	\| ------------ \| ------- \| -------------------------------------------------------------- \|
	\| `standalone` \| Yes \| Enables standalone mode with in-process scheduler and executor \|

	### ballista-core

	\| Feature \| Default \| Description \|
	\| ------------------------- \| ------- \| ---------------------------------------------------------------------- \|
	\| `arrow-ipc-optimizations` \| Yes \| Enables Arrow IPC optimizations for better shuffle performance \|
	\| `spark-compat` \| No \| Enables Spark compatibility mode via datafusion-spark \|
	\| `build-binary` \| No \| Required for building binary executables (AWS S3 support, CLI parsing) \|
	\| `force_hash_collisions` \| No \| Testing-only: forces all values to hash to same value \|

	### ballista-scheduler

	\| Feature \| Default \| Description \|
	\| -------------------------- \| ------- \| ------------------------------------------------ \|
	\| `build-binary` \| Yes \| Builds the scheduler binary with CLI and logging \|
	\| `substrait` \| No \| Enables Substrait plan support \|
	\| `prometheus-metrics` \| No \| Enables Prometheus metrics collection \|
	\| `graphviz-support` \| No \| Enables execution graph visualization \|
	\| `spark-compat` \| No \| Enables Spark compatibility mode \|
	\| `keda-scaler` \| No \| Kubernetes Event Driven Autoscaling integration \|
	\| `rest-api` \| No \| Enables REST API endpoints \|
	\| `disable-stage-plan-cache` \| No \| Disables caching of stage execution plans \|

	### ballista-executor

	\| Feature \| Default \| Description \|
	\| ------------------------- \| ------- \| ----------------------------------------------------- \|
	\| `arrow-ipc-optimizations` \| Yes \| Enables Arrow IPC optimizations \|
	\| `build-binary` \| Yes \| Builds the executor binary with CLI and logging \|
	\| `mimalloc` \| Yes \| Uses mimalloc memory allocator for better performance \|
	\| `spark-compat` \| No \| Enables Spark compatibility mode \|

	### ballista-cli

	\| Feature \| Default \| Description \|
	\| ------- \| ------- \| -------------------------------------------------- \|
	\| `tui` \| Yes \| Enables a REST client with Terminal User Interface \|

	![TUI Jobs table](./docs/source/user-guide/screenshots/tui-jobs-table.png)

	### Usage Examples

	```bash
	# Build with standalone support (default)
	cargo build -p ballista

	# Build with Substrait support
	cargo build -p ballista-scheduler --features substrait

	# Build with Spark compatibility
	cargo build -p ballista-executor --features spark-compat
	```

	## Project Status

	Ballista supports a wide range of SQL, including CTEs, Joins, and subqueries and can execute complex queries at scale,
	but still there is a gap between DataFusion and Ballista which we want to bridge in near future.

	Refer to the [DataFusion SQL Reference](https://datafusion.apache.org/user-guide/sql/index.html) for more
	information on supported SQL.

	## Who uses Ballista

	The following organizations use Ballista. To add yours, open a pull request.

	\| Organization \| \|
	\| ------------------------------------------------------------------------------------------------------------------------------ \| ------------------------------------------------------------- \|
	\| <a href="https://spice.ai"><img src="docs/source/_static/images/adopters/spiceai.png" height="36" alt="Spice AI"/></a> \| [Spice AI](https://spice.ai/blog/apache-ballista-at-spice-ai) \|
	\| <a href="https://coralogix.com"><img src="docs/source/_static/images/adopters/coralogix.png" height="36" alt="Coralogix"/></a> \| [Coralogix](https://coralogix.com/) \|

	## Contribution Guide

	Please see the [Contribution Guide](CONTRIBUTING.md) for information about contributing to Ballista.

	[user-guide]: https://datafusion.apache.org/ballista/