Authoring User Code

This section covers how to write the business logic for your Talon microservice. Topics are organized by functional area to help you find the right information quickly.

Overview

Talon microservices are event-driven applications that process messages within automatic transactions. Your user code defines:

• What consensus model to use - Event Sourcing or State Replication

• How to initialize - Lifecycle hooks and startup behavior

• How to process messages - Business logic in message handlers

• How to inject messages - Programmatic and scheduled injection

• How to expose commands - Administrative control points

• How to expose metrics - Custom telemetry and monitoring

Getting Started

New to Talon? Start here:

1. Consensus Model - Choose and configure your HA policy

2. Lifecycle - Understand initialization and shutdown

3. Message Processing - Write your first message handlers

4. Read Programming Fundamentals before writing handlers

Categories

Consensus Model

Configure your microservice's high availability and consensus behavior.

• Specifying The HA Policy - Choose Event Sourcing or State Replication

Lifecycle

Implement lifecycle methods that the Talon runtime invokes during your microservice's lifecycle.

Lifecycle methods include accessor methods (provide data to runtime), injection methods (receive runtime objects), and notification methods (handle lifecycle events).

• Implementing Lifecycle Methods - Implement accessor, injection, and notification methods

• Initializing the Microservice - Handle first and initial messages

Message Processing

Process inbound messages and execute business logic.

• Filtering Messages - Selectively process messages

• Processing Messages - Core message handling

  • Handling Messages - Write message handlers

  • Sending Messages - Send outbound messages

• Unhandled Messages - Handle messages with no registered handler

Message Injection

Programmatically create and inject messages for processing.

• Injecting Messages - Inject messages programmatically

• Scheduling Messages - Schedule future or periodic messages

Command and Control

Implement administrative commands for runtime control.

• Implementing Command Handlers - Create custom administrative commands

Monitoring

Expose custom statistics and telemetry from your microservice.

• Exposing Application Stats - Define custom metrics using @AppStat

Related Topics

• Microservice Template - Template-specific guidance for Event Sourcing and State Replication

• Configuring Messaging - Set up message bus connections and subscriptions

• Configuring the Microservice Runtime - Runtime configuration and tuning

• Concepts & Architecture - Understand how Talon works