Gatling

Gatling is a load and performance testing tool for web applications. Stéphane Landelle created it in 2012 as an open-source project, and Gatling Corp was later founded to provide enterprise features. Tests are written as code using DSLs available in Scala, Java, and Kotlin — scenarios describe user journeys with HTTP requests, pauses, and assertions that are version-controlled alongside application code.

The current release is Gatling 3.14. The tool uses a fully asynchronous, non-blocking architecture — virtual users are modeled as lightweight messages rather than threads, which allows a single machine to simulate thousands of concurrent users with low resource overhead. Beyond HTTP, Gatling supports WebSocket, Server-Sent Events, JMS, and gRPC protocols. After a test run, Gatling generates detailed HTML reports with response time distributions, throughput graphs, and error breakdowns.

The official documentation covers scenario design, protocol configuration, and CI integration. The source code is on GitHub under the Apache 2.0 license.