Configuring Agent Durability (Rust)

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:

use golem_rust::{agent_definition, agent_implementation};
 
#[agent_definition]
pub trait CounterAgent {
    fn new(name: String) -> Self;
    fn increment(&mut self) -> u32;
    fn get_count(&self) -> u32;
}
 
struct CounterAgentImpl {
    name: String,
    count: u32,
}
 
#[agent_implementation]
impl CounterAgent for CounterAgentImpl {
    fn new(name: String) -> Self {
        Self { name, count: 0 }
    }
 
    fn increment(&mut self) -> u32 {
        self.count += 1;
        self.count
    }
 
    fn get_count(&self) -> u32 {
        self.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

#[agent_definition(ephemeral)]
pub trait StatelessHandler {
    fn new() -> Self;
    fn handle(&self, input: String) -> String;
}

When to Choose Which

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