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# Apache Beam
[Apache Beam](http://beam.apache.org/) is a unified model for defining both batch and streaming data-parallel processing pipelines, as well as a set of language-specific SDKs for constructing pipelines and Runners for executing them on distributed processing backends, including [Apache Flink](http://flink.apache.org/), [Apache Spark](http://spark.apache.org/), [Google Cloud Dataflow](http://cloud.google.com/dataflow/), and [Hazelcast Jet](https://jet.hazelcast.org/).
## Status
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## Overview
Beam provides a general approach to expressing [embarrassingly parallel](https://en.wikipedia.org/wiki/Embarrassingly_parallel) data processing pipelines and supports three categories of users, each of which have relatively disparate backgrounds and needs.
1. _End Users_: Writing pipelines with an existing SDK, running it on an existing runner. These users want to focus on writing their application logic and have everything else just work.
2. _SDK Writers_: Developing a Beam SDK targeted at a specific user community (Java, Python, Scala, Go, R, graphical, etc). These users are language geeks and would prefer to be shielded from all the details of various runners and their implementations.
3. _Runner Writers_: Have an execution environment for distributed processing and would like to support programs written against the Beam Model. Would prefer to be shielded from details of multiple SDKs.
### The Beam Model
The model behind Beam evolved from several internal Google data processing projects, including [MapReduce](http://research.google.com/archive/mapreduce.html), [FlumeJava](http://research.google.com/pubs/pub35650.html), and [Millwheel](http://research.google.com/pubs/pub41378.html). This model was originally known as the [Dataflow Model](http://www.vldb.org/pvldb/vol8/p1792-Akidau.pdf).
To learn more about the Beam Model (though still under the original name of Dataflow), see the World Beyond Batch: [Streaming 101](https://www.oreilly.com/ideas/the-world-beyond-batch-streaming-101) and [Streaming 102](https://www.oreilly.com/ideas/the-world-beyond-batch-streaming-102) posts on OReillys Radar site, and the [VLDB 2015 paper](http://www.vldb.org/pvldb/vol8/p1792-Akidau.pdf).
The key concepts in the Beam programming model are:
* `PCollection`: represents a collection of data, which could be bounded or unbounded in size.
* `PTransform`: represents a computation that transforms input PCollections into output PCollections.
* `Pipeline`: manages a directed acyclic graph of PTransforms and PCollections that is ready for execution.
* `PipelineRunner`: specifies where and how the pipeline should execute.
### SDKs
Beam supports multiple language-specific SDKs for writing pipelines against the Beam Model.
Currently, this repository contains SDKs for Java, Python and Go.
Have ideas for new SDKs or DSLs? See the [sdk-ideas label](https://github.com/apache/beam/issues?q=is%3Aopen+is%3Aissue+label%3Asdk-ideas).
### Runners
Beam supports executing programs on multiple distributed processing backends through PipelineRunners. Currently, the following PipelineRunners are available:
- The `DirectRunner` runs the pipeline on your local machine.
- The `DataflowRunner` submits the pipeline to the [Google Cloud Dataflow](http://cloud.google.com/dataflow/).
- The `FlinkRunner` runs the pipeline on an Apache Flink cluster. The code has been donated from [dataArtisans/flink-dataflow](https://github.com/dataArtisans/flink-dataflow) and is now part of Beam.
- The `SparkRunner` runs the pipeline on an Apache Spark cluster.
- The `JetRunner` runs the pipeline on a Hazelcast Jet cluster. The code has been donated from [hazelcast/hazelcast-jet](https://github.com/hazelcast/hazelcast-jet) and is now part of Beam.
- The `Twister2Runner` runs the pipeline on a Twister2 cluster. The code has been donated from [DSC-SPIDAL/twister2](https://github.com/DSC-SPIDAL/twister2) and is now part of Beam.
Have ideas for new Runners? See the [runner-ideas label](https://github.com/apache/beam/issues?q=is%3Aopen+is%3Aissue+label%3Arunner-ideas).
Instructions for building and testing Beam itself
are in the [contribution guide](./CONTRIBUTING.md).
## “ Learn More
Here are some resources actively maintained by the Beam community to help you get started:
## Contact Us
To get involved with Apache Beam:
* [Subscribe to](https://beam.apache.org/community/contact-us/#:~:text=Subscribe%20and%20Unsubscribe) or e-mail the [user@beam.apache.org](http://mail-archives.apache.org/mod_mbox/beam-user/) list.
* [Subscribe to](https://beam.apache.org/community/contact-us/#:~:text=Subscribe%20and%20Unsubscribe) or e-mail the [dev@beam.apache.org](http://mail-archives.apache.org/mod_mbox/beam-dev/) list.
* [Join ASF Slack](https://s.apache.org/slack-invite) on [#beam channel](https://s.apache.org/beam-slack-channel)
* [Report an issue](https://github.com/apache/beam/issues/new/choose).