GoReplay (formerly known as Gor) is an open-source traffic replay and testing tool designed to capture real production traffic and replay it in test environments. It allows developers to use actual user interactions to vet applications under real-world conditions before deployment.

The main features and functionalities of GoReplay include:

Traffic Capture and Replay

• Reality-Driven Testing: Instead of using synthetic tests, GoReplay captures real production patterns to provide high-confidence testing.

• Shadow Testing: Users can see how code changes perform against real-world usage before they hit production.

• Load Testing: It eliminates guesswork by using real-world traffic scenarios to test if an application can handle specific loads.

• Capture Without Impact: Production traffic is captured without affecting the performance or experience of live users.

Traffic Management and Shaping

• Session-Aware Replay: The tool preserves distinct user sessions, handles connection pooling, and optimizes TLS handling to match real user patterns.

• Traffic Filtering and Transformation: Users can filter, transform, and direct traffic according to specific rules, providing complete control over the flow.

• Comparison Testing: It can redirect captured traffic to multiple versions of a service simultaneously to compare their performance and behavior under identical load conditions.

Infrastructure and Monitoring

• Infrastructure Validation: It is used for migration testing (e.g., moving from RackSpace to Azure) to accurately estimate requirements and highlight flaws in new setups.

• Monitoring and Analytics: Provides real-time insights into every request, enabling pattern detection and proactive alerts.

• Simplicity: The tool is designed for ease of use, often requiring only one command (e.g., gor --input-raw :8080 --output-http="...") to begin testing.

Open Source vs. Enterprise Editions

• Open Source: Provides basic HTTP traffic capture and replay, a command-line interface, and community support under the LGPLv3 license.

• Enterprise (Pro): Includes advanced features such as Websocket support, data masking for security, advanced traffic storage, and an analytics dashboard.