Configuring Agent Durability (Scala)

Durable Agents (Default)

By default, all Golem agents are durable:

State persists across invocations, failures, and restarts
Every side effect is recorded in an oplog (operation log)
On failure, the agent is transparently recovered by replaying the oplog
No special code needed — durability is automatic

A standard durable agent:

import golem.runtime.annotations.{agentDefinition, agentImplementation}
import golem.BaseAgent
 
import scala.concurrent.Future
 
@agentDefinition(mount = "/counters/{name}")
trait CounterAgent extends BaseAgent {
  class Id(val name: String)
  def increment(): Future[Int]
  def getCount(): Future[Int]
}
 
@agentImplementation()
final class CounterAgentImpl(private val name: String) extends CounterAgent {
  private var count: Int = 0
 
  override def increment(): Future[Int] = Future.successful {
    count += 1
    count
  }
 
  override def getCount(): Future[Int] = Future.successful(count)
}

Ephemeral Agents

Use ephemeral mode for stateless, per-invocation agents where persistence is not needed:

State is discarded after each invocation completes
No oplog is maintained — lower overhead
Useful for pure functions, request handlers, or adapters

import golem.runtime.annotations.{agentDefinition, DurabilityMode}
 
@agentDefinition(mode = DurabilityMode.Ephemeral)
trait StatelessHandler extends BaseAgent {
  def handle(input: String): Future[String]
}

When to Choose Which

Use Case	Mode
Counter, shopping cart, workflow orchestrator	Durable (default)
Stateless request processor, transformer	Ephemeral
Long-running saga or multi-step pipeline	Durable (default)
Pure computation, no side effects worth persisting	Ephemeral
Agent that calls external APIs with at-least-once semantics	Durable (default)

When in doubt, use the default (durable). Ephemeral mode is an optimization for agents that genuinely don't need persistence.

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