Beginner's guide to Apache Flink
Tags: flink, dataengineering, dataprocessing
Published: 2024-01-08 14:28:42

Apache Flink is a powerful and versatile open-source stream processing framework that goes beyond traditional batch processing to handle real-time data streaming and analytics. In this article, we will explore the fundamental concepts of Apache Flink, compare batch and stream processing, highlight the differences between Flink and Apache Spark, delve into system requirements, installation procedures, Maven usage, and discuss Flink's APIs and transformations.

## Understanding Apache Flink
<img width="100%" style="width:100%" src="https://media.giphy.com/media/f6z5TkrTIBZILYOd1t/giphy.gif">

### What is Apache Flink?

Apache Flink is a distributed stream processing framework designed for big data processing and analytics. It excels in handling large volumes of data with low-latency processing capabilities, making it suitable for real-time applications. Flink supports event time processing, fault-tolerance, and stateful processing, enabling developers to build robust and scalable data processing applications.

## Batch Processing vs. Stream Processing

### Batch Processing

Batch processing involves processing data in chunks or batches at a time. It is suitable for scenarios where data can be collected and processed in a non-continuous manner. Examples of batch processing include nightly ETL (Extract, Transform, Load) jobs, data warehousing, and large-scale data analysis.

### Stream Processing

Stream processing deals with the continuous and real-time processing of data as it is generated. It is ideal for scenarios where low-latency and near-real-time insights are crucial. 
Examples of stream processing include fraud detection, monitoring systems, and real-time analytics on social media feeds.


![Image description of batch vs stream analytics[](url)](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/t3oi1ha4erwm89uih7uy.png)

## Apache Flink vs. Apache Spark

### Core Differences

While both Apache Flink and Apache Spark are powerful big data processing frameworks, they have some key differences:

- **Processing Model:**
  - Flink focuses on event time processing and supports true event-driven stream processing.
  - Spark primarily follows a micro-batch processing model, which introduces slight latency in stream processing.

- **State Management:**
  - Flink emphasizes on stateful processing, offering built-in support for managing state.
  - Spark typically relies on external storage solutions for state management.

- **Fault Tolerance:**
  - Flink achieves fault tolerance through distributed snapshots and state replication.
  - Spark employs lineage information and recomputation for fault tolerance.

## Layers of Apache Flink Ecosystem

![Apache Flink Ecosystem](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/vh3s0be288c9waxmzmzv.png)


## Apache Flink System Requirements

Before diving into Apache Flink, ensure that your system meets the following requirements:

- **Java:** Flink is a Java-based framework, so ensure that Java is installed on your machine.
- **Memory:** Sufficient RAM to accommodate Flink's processes.
- **Disk Space:** Adequate disk space for Flink's data storage requirements.

## Installation and Maven Usage

### Installing Apache Flink

1. **Download:**
   - Visit the [Apache Flink download page](https://flink.apache.org/downloads.html) and select the desired version.
   - Follow the installation instructions provided for your operating system.

2. **Configuration:**
   - Customize Flink's configuration files based on your specific requirements.

### Using Maven with Apache Flink

Maven simplifies the management of project dependencies and builds. To use Flink with Maven:

 **Add Dependency:**
   - Include the Flink dependency in your `pom.xml` file:

   ```xml
   <dependencies>
       <dependency>
           <groupId>org.apache.flink</groupId>
           <artifactId>flink-java</artifactId>
           <version>${flink.version}</version>
       </dependency>
   </dependencies>
```

**Or**
**You can create a project based on an Archetype with the Maven command below:**
```
$ mvn archetype:generate                \
  -DarchetypeGroupId=org.apache.flink   \
  -DarchetypeArtifactId=flink-quickstart-java \
  -DarchetypeVersion=1.18.0
```

## Build and Run

To compile and execute your Apache Flink project, follow these steps:

1. **Build Project:**
   Execute the following Maven command to build your Flink project:

   ```bash
   mvn clean package 
```
Run the Flink application using the generated JAR file.


## Apache Flink APIs and Transformations

### Flink APIs

Flink provides high-level APIs for Java and Scala:

- **DataStream API:** Used for stream processing applications.
Supported by Java, Scala and Python

- **DataSet API:** Designed for batch processing applications.
Supported by Java and Scala



### Data Sources for DataStream API
<img width="100%" style="width:100%" src="https://media.giphy.com/media/13hFjqkckEAxzy/giphy.gif">

The DataStream API in Apache Flink supports various data sources for stream processing applications. Common data sources include:

- **Kafka:** Flink can consume and process data from Kafka topics in real-time.
- **Socket Streams:** Flink allows the ingestion of data from socket streams, making it versatile for various streaming scenarios.
- **File Systems:** Data can be read from various file systems, such as HDFS or local file systems, providing flexibility in handling different data storage formats.


### Transformations in Flink

Flink transformations are the building blocks of data processing pipelines. Key transformations include:

- **Map:** Applies a function to each element in the dataset.
- **Filter:** Retains elements satisfying a specified condition.
- **KeyBy:** Groups elements based on a key.
- **Window:** Defines time or count-based windows for stream processing.
- **Reduce:** Aggregates elements in a window.

## Conclusion

Let's create a project!