🚀 Azure Functions In-Proc Response Compression (POC)

This repository contains a proof of concept (POC) demonstrating how to implement response compression (Gzip and Brotli) in Azure Functions (In-Process model). It enables HTTP-triggered functions to return compressed responses based on the Accept-Encoding header.

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📌 Purpose

Optimize Azure Function responses by reducing payload sizes, improving transfer speeds, and supporting clients with modern compression algorithms.

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✨ Features

• ✅ In-process Azure Functions using .NET 8
• ✅ Supports Gzip and Brotli compression
• ✅ Detects Accept-Encoding from incoming requests
• ✅ Applies dynamic compression on JSON/text payloads
• ✅ Uses Newtonsoft.Json for serialization
• ✅ Lightweight and extensible structure

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🧱 Project Structure

ResponseCompression/
├── Properties/
│   ├── launchSettings.json
│   └── serviceDependencies.json
├── Extensions/
│   └── AzureFunctionsInProcessCompressionExtensions.cs
├── Functions/
│   └── CompressedJsonFunction.cs
├── GlobalUsings.cs
├── host.json
├── local.settings.json
├── .gitignore
└── README.md

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🏗️ Tech Stack

• Azure Functions (In-Proc)
• .NET 8
• System.IO.Compression
• Newtonsoft.Json

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🚀 Running Locally

🔧 Prerequisites

• .NET 8 SDK
• Azure Functions Core Tools
• Visual Studio 2022+ or VS Code

▶️ Start the Function App

func start

By default, the function runs on:

http://localhost:7169

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📤 Example Usage with curl

🗜️ Gzip

curl -H "Accept-Encoding: gzip" http://localhost:7169/api/compressed-json --output response.gz

🗜️ Brotli

curl -H "Accept-Encoding: br" http://localhost:7169/api/compressed-json --output response.br

🧾 No Compression

curl http://localhost:7169/api/compressed-json

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🧠 How It Works

1. CompressedJsonFunction receives the HTTP request
2. Reads the Accept-Encoding header
3. Serializes the response using Newtonsoft.Json
4. Applies compression (Gzip or Brotli) using System.IO.Compression
5. Sets appropriate Content-Encoding and Content-Type headers
6. Returns the compressed stream as the response

➡️ Compression logic is encapsulated in:
Extensions/AzureFunctionsInProcessCompressionExtensions.cs

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📚 References

• Azure Functions HTTP Trigger
• GzipStream Documentation
• BrotliStream Documentation
• Newtonsoft.Json Documentation

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❗ Limitations

• Designed for the in-process model only
• Not suitable for binary or large media content
• ASP.NET Core middleware pipeline is not available in in-proc model

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🙌 Contributions

Feel free to fork, extend, and improve this POC. Pull requests are welcome!