README.md

Activities

This section covers defining and implementing Temporal activities in Kotlin.

Overview

Activities are the building blocks for interacting with external systems. The Kotlin SDK provides type-safe activity execution with suspend function support.

Documents

Document	Description
Definition	Activity interfaces, typed and string-based execution
Implementation	Implementing activities, KActivity API, heartbeating
Local Activities	Short-lived local activities

Quick Reference

Basic Activity

// Define activity interface - @ActivityMethod is optional
@ActivityInterface
interface GreetingActivities {
    suspend fun composeGreeting(greeting: String, name: String): String
}

// Use @ActivityMethod only when customizing the activity name
@ActivityInterface
interface CustomNameActivities {
    @ActivityMethod(name = "compose-greeting")
    suspend fun composeGreeting(greeting: String, name: String): String
}

// Implement activity
class GreetingActivitiesImpl : GreetingActivities {
    override suspend fun composeGreeting(greeting: String, name: String): String {
        return "$greeting, $name!"
    }
}

Calling Activities from Workflows

// Type-safe method reference
val greeting = KWorkflow.executeActivity(
    GreetingActivities::composeGreeting,
    KActivityOptions(startToCloseTimeout = 30.seconds),
    "Hello", "World"
)

// String-based (for cross-language interop)
val result = KWorkflow.executeActivity<String>(
    "composeGreeting",
    KActivityOptions(startToCloseTimeout = 30.seconds),
    "Hello", "World"
)

Key Patterns

Pattern	API
Execute activity	KWorkflow.executeActivity(Interface::method, options, args)
Execute by name	KWorkflow.executeActivity<R>("name", options, args)
Local activity	KWorkflow.executeLocalActivity(Interface::method, options, args)
Heartbeat	KActivity.executionContext.heartbeat(details)

Related

• Implementation - Suspend activity patterns
• Local Activities - Short-lived activities

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