Goreplay

GoReplay (often written as “GoReplay” or “goreplay”) is an open-source tool designed for capturing and replaying live HTTP traffic. It allows you to record your web traffic and then replay it in a controlled environment, which can be incredibly useful for testing, debugging, and performance evaluation.

Why GoReplay is Useful

1. Testing:
   • Load Testing: Recreate production traffic to test the performance and scalability of your application under real-world conditions.
   • Regression Testing: Ensure that recent changes have not introduced new bugs by replaying previous traffic.
   • A/B Testing: Compare how different versions of your application handle the same traffic.
2. Debugging:
   • Error Replication: Replay traffic that caused errors in the production environment to understand and fix the issues in a test environment.
   • Latency Analysis: Analyze how different parts of your application respond to real traffic.
3. Performance Tuning:
   • Bottleneck Identification: Identify performance bottlenecks by analyzing how your application handles various loads.
   • Infrastructure Optimization: Test different configurations and setups to find the most efficient infrastructure for handling your traffic.

How to Use GoReplay

Installation

GoReplay can be installed via various methods, including using pre-built binaries, Docker, or compiling from source. Here are some common installation methods:

1. Using Pre-built Binaries:
   • Download the appropriate binary for your operating system from the GoReplay GitHub releases page.
   • Extract the binary and move it to a directory in your system’s PATH.
2. Using Docker:

   docker pull goreplay/goreplay
   

3. Building from Source:
   • Ensure you have Go installed.
   • Clone the repository and build the binary:

     git clone https://github.com/buger/goreplay.git
     cd goreplay
     make
     

Basic Usage

1. Recording Traffic:

   goreplay --input-raw :80 --output-file ./requests.gor
   

   This command captures HTTP traffic on port 80 and saves it to a file called requests.gor.

2. Replaying Traffic:

   goreplay --input-file ./requests.gor --output-http "http://your.test.server"
   

   This command replays the recorded traffic to the specified server.

3. Mirroring Traffic:

   goreplay --input-raw :80 --output-http "http://staging.server"
   

   This command captures live traffic on port 80 and mirrors it to a staging server.

4. Capturing Traffic and Outputting to Stdout:

   goreplay --input-raw :80 --output-stdout
   

   This command captures HTTP traffic on port 80 and outputs it directly to the console (stdout).

5. Capturing Traffic, Saving to File, and Outputting to Stdout:

   goreplay --input-raw :80 --output-file ./requests.gor --output-stdout
   

   This command captures HTTP traffic on port 80, saves it to requests.gor, and also outputs it to the console.

In summary, the updated diagram and examples provide a clear understanding of how GoReplay captures traffic, outputs it to stdout, and records it for replay. This can be particularly useful for real-time monitoring and debugging.

Advanced Usage

• Filtering Traffic: You can filter traffic based on various criteria, such as headers, methods, or URLs.

  goreplay --input-raw :80 --output-http "http://staging.server" --http-allow-url ^/api
  

  This command only captures and replays traffic that matches the specified URL pattern.

• Modifying Traffic: Modify traffic during replay, such as changing headers or payloads.

  goreplay --input-file ./requests.gor --output-http "http://staging.server" --middleware "./modify_script.sh"
  

• Throttling Traffic: Control the rate at which traffic is replayed.

  goreplay --input-file ./requests.gor --output-http "http://staging.server" --output-http-workers 5
  

basic workflow of GoReplay, including capturing, recording, replaying traffic and standard output (stdout) process, showcasing how captured traffic can be directly output to the console.

Explanation:

1. Live Traffic: Represents incoming HTTP requests.
2. GoReplay: The main tool capturing and replaying traffic.
3. Stdout: Standard output where captured traffic can be directly output to the console.
4. Requests.gor File: A file where the captured traffic is recorded.
5. Test Server: The server where traffic is replayed for testing.
6. **Staging Server: Server where live traffic is mirrored for testing.

Components within GoReplay:

• Capture Module: Captures live HTTP traffic.
• Replay Module: Replays the captured traffic to the test server.
• Stdout: Provides an option to output captured traffic directly to the console.

TODO add screenshots

Conclusion

GoReplay is a powerful tool for capturing, replaying, and analyzing HTTP traffic. It is particularly useful for testing, debugging, and optimizing web applications by allowing developers to replicate real-world traffic scenarios. By incorporating GoReplay into your development and testing workflows, you can improve the reliability and performance of your applications.