Communication II: Building and Integrating Custom RPC Handlers

Module Overview

Welcome to Module 07 of the XRPL Core Dev Bootcamp! This module focuses on the practical implementation of custom RPC (Remote Procedure Call) handlers within the Rippled codebase.

Building upon Module 06 where you learned about RPC architecture, request flows, authentication, and error handling patterns, you will now learn how to design, implement, and integrate your own RPC handlers into the XRP Ledger node software. This hands-on module bridges theory and practice, empowering you to extend Rippled's API capabilities with custom functionality.

What You Will Learn

By the end of this module, you will be able to:

  • Implement Custom RPC Handlers: Write complete handler functions following XRPL conventions, including request parsing, validation, and response formatting.

  • Apply Security Patterns: Implement role-based access control and resource management in your custom handlers.

  • Build Error Handling: Create comprehensive error handling with proper HTTP status codes and JSON-RPC error responses.

  • Test Your Implementation: Write unit tests and integration tests to ensure your custom handlers work correctly under various conditions.

  • Integrate with the Ledger: Access ledger data, account information, and transaction history through the proper context APIs.

  • Follow Best Practices: Apply established patterns from existing handlers to ensure maintainability and code quality.

  • Work with Advanced Features: Implement streaming responses, subscriptions, and batch processing.

Prerequisites

Before starting this module, you should have:

  • ✅ REQUIRED: Completed Module 06 (Communication I: Understanding XRPL(d) RPC Architecture)

  • ✅ Completed Module 01-05 (Understanding Rippled architecture and core components)

  • ✅ Strong understanding of C++20 features and best practices

  • ✅ Understanding of XRP Ledger data structures (accounts, ledgers, transactions)

  • ✅ Experience with unit testing frameworks (Google Test recommended)

Module Structure

This module is organized into the following sections:

📚 Architecture Foundation (from Module 06)

Before implementing custom handlers, make sure you've completed Module 06 which covers:

📚 Implementation Topics

  1. Implementing Custom Handlers

    • Handler function signatures

    • Input validation patterns

    • Ledger access and queries

    • Result construction

    • Code organization

  2. Testing RPC Handlers

    • Unit test structure

    • Mock objects and fixtures

    • Integration testing

    • Edge case coverage

  3. Advanced Features

    • Streaming responses

    • Subscription mechanisms

    • Batch request processing

    • gRPC integration

  4. Best Practices and Patterns

    • Code style guidelines

    • Common pitfalls to avoid

    • Performance considerations

    • Documentation standards

Hands-On Exercise

🛠️ Workshop: Building GetAccountBalance Handler

As part of this module, you will complete a comprehensive workshop where you'll implement a new RPC command called GetAccountBalance from scratch.

This exercise covers:

  • Handler registration in the central table

  • Request/response type definitions

  • Complete handler implementation

  • Comprehensive error handling

  • Unit test creation

Start the Workshop →

Video Lecture

[VIDEO_PLACEHOLDER]

Watch Denis explain the core concepts of building and integrating custom RPC handlers in Rippled.

Key Concepts Covered

Throughout this module, you'll work with these essential components:

Concept
Description
Source Location

Handler Table

Central registry of all RPC commands

src/xrpld/rpc/handlers/Handlers.cpp

JsonContext

Request context with ledger access

src/xrpld/rpc/detail/RPCHelpers.h

Role System

Permission levels for API access

src/xrpld/core/Config.h

Error Codes

Standard JSON-RPC error responses

src/xrpld/rpc/detail/RPCErrors.h

Handler Pattern

Standard function signature

src/xrpld/rpc/handlers/

Practical Applications

Understanding RPC handler implementation enables you to:

  • Extend Rippled Functionality: Add custom queries and operations tailored to specific use cases

  • Build Developer Tools: Create specialized endpoints for debugging, monitoring, or analytics

  • Prototype New Features: Rapidly test ideas for protocol improvements

  • Integrate External Systems: Bridge Rippled with custom middleware or services

  • Contribute to XRPL: Submit handler improvements or new commands to the official repository

Additional Resources

Navigation

⬅️ Previous Module: Communication I | Next Module: Consensus I →

Get Help

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Table of Contents

Architecture Foundation (Module 06)

  1. RPC Handler Architecture

  2. Request and Response Flow

  3. Authentication and Authorization

  4. Error Handling and Validation

Implementation (Module 07)

  1. Implementing Custom Handlers

  2. Testing RPC Handlers

  3. Advanced Features

  4. Best Practices and Patterns

  5. Workshop Exercise

  6. Appendices

Ready to build your first RPC handler? Let's begin!

Start with Implementing Custom Handlers →

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