Ktor Advanced Demo: The Pit Crew

A Kotlin Multiplatform (KMP) showcase focusing on industrial-grade HttpClient configuration. This project demonstrates how to offload common networking concerns—authentication, retries, logging, and serialization—to Ktor's powerful plugin architecture.

"One client, configured once, shared as a singleton — the rest of the code never has to think about auth headers, retry logic, or JSON parsing. That's the pit crew doing its job."

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🛠️ The "Pit Crew" (Key Features)

This demo centralizes network logic in HttpClientFactory.kt, implementing a robust pipeline of plugins:

1. 📋 Dynamic Logging: Uses LogLevel.ALL in debug for full visibility into request/response bodies, and LogLevel.NONE in production for zero overhead.
2. 🔄 Content Negotiation: Powered by kotlinx.serialization with lenient JSON parsing to survive minor backend inconsistencies and future-proof against new fields.
3. 🔐 Transparent Auth (Bearer):
   • Auto-loading: Attaches tokens automatically to outgoing requests.
   • Auto-refresh: Intercepts 401 Unauthorized responses, refreshes tokens via TokenStorage, and retries the original request without any manual intervention in repositories.
   • Exclusion logic: Smartly skips authentication for specific endpoints (e.g., login/register).
4. 🌐 Centralized Defaults: Sets the base URL (JSONPlaceholder) and default headers (Content-Type, Accept) globally.
5. 🔁 Intelligent Retries:
   • Automatically retries safe (idempotent) methods (GET, PUT, DELETE).
   • Implements Exponential Back-off (2s → 4s → 8s) to handle transient server errors (5xx).
   • Intentionally excludes POST requests to prevent accidental duplicate resource creation.

🏗️ Project Structure

• shared/commonMain:
  • network/HttpClientFactory.kt: The heart of the networking layer.
  • network/TokenStorage.kt: Contract for token management.
  • network/PostsRepository.kt: Clean, logic-free data fetching.
  • App: Compose Multiplatform UI demonstrating the network state.

🚀 Tech Stack

• Kotlin Multiplatform (KMP)
• Ktor 3.1.3: Core networking engine.
• Compose Multiplatform: Shared UI layer.
• Kotlinx Serialization: JSON processing.
• Material 3: Modern UI components.

🏁 Getting Started

Prerequisites

• Android Studio Ladybug (or newer)
• Kotlin 2.1.0+
• macOS (if running the iOS target)

Running the App

1. Android: Select the androidApp configuration and hit Run.
2. iOS: Open the iosApp folder in Xcode or run from Android Studio using the KMP plugin.

Experimenting

• Toggle Debug Mode in the UI to see how Logging and prettyPrint behavior changes in the Logcat.
• Check HttpClientFactory.kt to modify retry counts or base URLs.

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This demo is part of an article series on advanced Kotlin Multiplatform networking. For a deep dive into the implementation details, check out the full post.