--- title: "OpenResty and Kong: A First Look at the High-Performance Web Platform and API Gateway" description: "An introduction to OpenResty and Kong — from the high-performance web platform to the API Gateway, plus practical container debugging tips so you can ramp up fast and operate smoothly." canonical_url: "https://blog.markkulab.net/en/post/openresty-kong-api-gateway" author: "Mark Ku" author_url: "https://blog.markkulab.net/en/author/mark-ku" site: "Mark Ku's Tech Notes" date_published: "2025-07-13 01:01:00 +0800" category: "DevOps" tags: ["openresty", "kong", "nginx", "api gateway", "lua", "docker", "devops"] language: "en" license: "CC BY 4.0" license_url: "https://creativecommons.org/licenses/by/4.0/" attribution: "when reusing or quoting, credit the author and link back to the original" --- # OpenResty and Kong: A First Look at the High-Performance Web Platform and API Gateway ## OpenResty and Kong: A First Look at the High-Performance Web Platform and API Gateway When building websites and APIs today, performance and flexibility are top concerns. OpenResty is Nginx + Lua scripting — it goes beyond static proxying so you can flexibly handle all sorts of needs. Kong is an API Gateway built on OpenResty, used by many startups and large companies alike. This article is a casual walkthrough of OpenResty and Kong, plus how to debug them in containers. ## What is OpenResty? In short: OpenResty is Nginx + Lua. You can write scripts to extend functionality — API Gateway, reverse proxy, even a WAF (Web Application Firewall) — no problem. ### What's so great about OpenResty? - **Super high performance**: Nginx is already fast; add Lua scripts and you get flexibility plus speed. - **Easy to extend**: edit a Lua script and reload — no recompilation. - **Big ecosystem**: many ready-made Lua modules — auth, caching, API management, etc. - **Versatile**: API Gateway, reverse proxy, WAF, log collection — all doable. ### Who is it for? - Teams wanting a high-performance API Gateway or reverse proxy - Engineers who want to extend Nginx quickly with Lua - Folks doing microservices and DevOps ## What can you build with OpenResty? - API Gateway - Dynamic websites - Reverse proxy and load balancing - WAF (Web Application Firewall) - Log and monitoring collection ## Kong: an API Gateway built on OpenResty Kong uses OpenResty under the hood, then modularizes API management, auth, and traffic control. Adding features means installing a plugin — super convenient. ### What makes Kong special? - **Pluggable**: features as plugins — add what you need. - **High performance**: built on OpenResty/Nginx — speed isn't a question. - **Distributed and cloud-native**: runs on K8s and Docker — very flexible. - **Active community**: plenty of folks online to discuss issues with. ### How does Kong relate to OpenResty? Kong takes OpenResty's flexibility to the limit, so you don't have to write Lua to handle most API Gateway needs. ## How do you debug OpenResty and Kong? 1. **Check the Error Log** - Usually at `/usr/local/openresty/nginx/logs/error.log` or `/var/log/nginx/error.log` - Good for: initial debugging 2. **Enable Debug Log** - Kong: set `log_level = debug` in `kong.conf` - OpenResty: set `error_log ... debug;` in `nginx.conf` - Good for: seeing finer execution flow 3. **Add log calls in Lua scripts** - `ngx.log(ngx.ERR, "Debug info: ", cjson.encode(var))` - Good for: tracing variables and flow 4. **API testing** - Use Postman/curl to call APIs and inspect responses - Good for: validating plugins, routes, auth 5. **Plugin ordering** - Kong's plugins have order — wrong order behaves weirdly 6. **Official docs / community** - OpenResty: https://openresty.org/ - Kong: https://docs.konghq.com/ ### Remote debugging in containers (Docker) 1. **Get inside the container and tail logs** ```bash docker exec -it openresty-container /bin/sh tail -f /usr/local/openresty/nginx/logs/error.log ``` 2. **View container logs directly** ```bash docker logs -f openresty-container ``` 3. **Mount a local directory** ```bash docker run -v /your/local/logs:/usr/local/openresty/nginx/logs ... openresty ``` 4. **Capture traffic** ```bash sudo tcpdump -i docker0 port 8080 ``` 5. **VSCode Remote - Containers** - Edit and debug files inside the container directly from VSCode — super convenient #### Common debugging tips - Bad nginx.conf (test with `nginx -t`) - Container network not connected - Lua script bugs or missing modules - Wrong plugin order --- ## Closing OpenResty supercharges Nginx, and Kong takes API Gateway to the next level. If you have API management, traffic control, or auth needs, both tools are well worth a spin. When issues come up, lean on logs and the community — debugging isn't hard! Questions? Drop a comment — let's level up together! --- ## About this article and its author Originally published on [Mark Ku's Tech Notes](https://blog.markkulab.net/en/post/openresty-kong-api-gateway) License: [CC BY 4.0](https://creativecommons.org/licenses/by/4.0/) — when reusing or quoting, credit the author and link back to the original ### About the author **[Mark Ku](https://blog.markkulab.net/en/author/mark-ku)** — Software Solution Provider - 10+ years senior software engineer, now an AI Builder - Focused on large-platform architecture — North-American e-commerce, AI SaaS subscription billing - Combining AI Agents and automation to build evolvable product foundations ### Free tools built by the author All of these are free to use: - [Free PDF Sign Tool](https://blog.markkulab.net/en/tools/pdf-sign): Online PDF sign tool — draw, type, or upload a signature, then drag, resize, and download. 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No sign-up, nothing uploaded to a server, and mermaid.live share links work as-is. - [React Intl Phone Number](https://blog.markkulab.net/en/tools/react-intl-phone-number): react-intl-phone-number is an open-source React component: framework-agnostic and antd-free, with E.164 in/out, a searchable flag / country-code dropdown, configurable validation levels (strict / mobile-strict / loose), themeable CSS, and i18n — phone logic powered by google-libphonenumber. Lightweight and fully typed. Free and open source (MIT). - [Uptime Kuma Cluster](https://blog.markkulab.net/en/tools/uptime-kuma-cluster): Turn single-node Uptime Kuma into a highly available cluster: OpenResty + Lua smart load balancing, shared MariaDB state, health checks and automatic failover, plus cluster-management REST APIs. One Docker Compose command to start. 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