cassowary
Cassowary is a lightweight, cross-platform HTTP load testing CLI tool written in Go. It supports multiple concurrent users, file-based URL patterns, and exports metrics to Prometheus, Cloudwatch, and JSON formats.
Key facts
Objective fields from the source. Values we can't verify are shown as “Unknown” rather than guessed.
| Field | Value |
|---|---|
| Repository | rogerwelin/cassowary |
| Owner | rogerwelin |
| Primary language | Go |
| License | MIT — OSI-approved |
| Stars | 811 |
| Forks | 41 |
| Open issues | 7 |
| Latest release | v0.19.0 (2025-06-10) |
| Last updated | 2025-09-11 |
| Source | https://github.com/rogerwelin/cassowary |
What cassowary is
Go-based HTTP/S load testing tool offering configurable concurrency, multiple HTTP methods (GET, POST, PUT, PATCH), distributed load testing capability, and metric export to Prometheus PushGateway and AWS Cloudwatch. Importable as a Go module for programmatic use.
Get the cassowary source
Clone the repository and explore it locally.
git clone https://github.com/rogerwelin/cassowary.gitcd cassowary# follow the project's README for install & configurationNeed it deployed, integrated, or customized instead? DEV.co ships production installs.
Best use cases
Implementation considerations
- Go binary is self-contained; no runtime dependencies, but verify compatibility with your OS/architecture before deployment.
- Concurrency model: confirm load distribution aligns with your target application's connection pooling and resource constraints.
- Metric export to Prometheus requires accessible PushGateway; Cloudwatch export requires AWS credentials and IAM permissions.
- File slurp mode supports HTTP-fetched URL lists; ensure source URLs are reliable and authenticated if required.
- Request body (POST/PUT/PATCH) sourced from files; validate file encoding and size limits for large payloads.
When to avoid it — and what to weigh
- Complex Scripting Requirements — Cassowary is a purpose-built CLI tool; if you need JavaScript-based scripting, request lifecycle hooks, or complex test logic, k6 may be more suitable.
- Enterprise Load Testing at Scale — Unknown whether Cassowary offers cloud-based coordination or SaaS capabilities; large-scale distributed testing may require external orchestration.
- Real-time Browser Testing — Cassowary does HTTP-only testing; cannot simulate browser behavior, JavaScript execution, or client-side rendering performance.
- Stateful Protocol Testing — No indication of support for WebSocket, gRPC, or other non-HTTP protocols; limited to HTTP/S requests.
License & commercial use
MIT License (permissive OSI license): allows commercial use, modification, and distribution with attribution and liability disclaimer.
MIT license permits commercial use without royalties. Typical commercial applications (CI/CD pipelines, SaaS load testing services) are allowed. Consult internal legal review if incorporating source code into proprietary products. No commercial support model evident from data provided.
DEV.co evaluation signals
Editorial assessment — not user reviews. Directional, with an explicit confidence level.
| Signal | Assessment |
|---|---|
| Maintenance | Active |
| Documentation | Adequate |
| License clarity | Clear |
| Deployment complexity | Low |
| DEV.co fit | Good |
| Assessment confidence | High |
Supports x509 authentication and arbitrary HTTP headers (enables mTLS, custom auth headers). HTTPS supported. No security audit data provided. Verify certificate validation behavior for self-signed/internal CAs. Cloudwatch export and credential handling depend on host OS security practices.
Alternatives to consider
k6
Feature-rich JavaScript-based load testing with scripting, lifecycle hooks, and cloud orchestration; better for complex scenarios but heavier resource footprint.
Apache JMeter
Mature, GUI-based load testing tool with extensive protocol support; better for non-technical users and complex test plans, but higher operational overhead.
wrk/wrk2
Lightweight HTTP load testing with Lua scripting; similar binary size and performance focus, but smaller ecosystem and community than Cassowary.
Build on cassowary with DEV.co software developers
Cassowary integrates directly into CI pipelines and DevOps workflows. Our team can help architect scalable performance testing infrastructure using Cassowary or evaluate alternatives.
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cassowary FAQ
Can I use Cassowary in a Docker container for CI/CD?
Does Cassowary support WebSocket or gRPC?
How do I export results for analysis?
Is Cassowary suitable for distributed load testing?
Work with a software development agency
Need help beyond evaluating cassowary? DEV.co is a software development agency offering software development services and web development for teams of every size. Our software developers and web developers build custom software, web applications, APIs, and open-source testing integrations — and maintain them long-term.
Need Production-Ready Load Testing?
Cassowary integrates directly into CI pipelines and DevOps workflows. Our team can help architect scalable performance testing infrastructure using Cassowary or evaluate alternatives.