Adding Resource Quotas to an Agent (Rust)

Golem provides a distributed resource quota system via golem_rust::quota. Quotas let you define limited resources (API call rates, storage capacity, connection concurrency) and enforce consumption limits across all agents in a deployment.

1. Define Resources in the Application Manifest

Add resource definitions under resourceDefaults in golem.yaml, scoped per environment:

resourceDefaults:
  prod:
    api-calls:
      limit:
        type: Rate
        value: 100
        period: minute
        max: 1000
      enforcementAction: reject
      unit: request
      units: requests
    storage:
      limit:
        type: Capacity
        value: 1073741824  # 1 GB
      enforcementAction: reject
      unit: byte
      units: bytes
    connections:
      limit:
        type: Concurrency
        value: 50
      enforcementAction: throttle
      unit: connection
      units: connections

Limit Types

• Rate — refills value tokens every period (second/minute/hour/day), capped at max. Use for rate-limiting API calls.
• Capacity — fixed pool of value tokens. Once consumed, never refilled. Use for storage budgets.
• Concurrency — pool of value tokens returned when released. Use for limiting parallel connections.

Enforcement Actions

• reject — returns Err(FailedReservation) with an optional estimated wait time. The agent must handle the error.
• throttle — Golem suspends the agent until capacity is available. Fully automatic, no code needed.
• terminate — kills the agent with a failure message.

2. Acquire a QuotaToken

Acquire a QuotaToken once per resource, typically in the agent constructor:

use golem_rust::quota::QuotaToken;
 
let token = QuotaToken::new("api-calls", 1);

The second parameter is the expected amount per reservation, used for fair scheduling. For simple 1-call = 1-token rate limiting, use 1.

3. Simple Rate Limiting with with_reservation

Use with_reservation to reserve tokens, run code, and commit actual usage:

use golem_rust::quota::with_reservation;
 
let result = with_reservation(&token, 1, |_reservation| {
    let response = call_simple_api();
    (1, response)
});

The closure returns (actual_used, value). If actual_used < reserved, unused capacity returns to the pool.

4. Variable-Cost Reservations (e.g., LLM Tokens)

Reserve the maximum expected cost, then commit actual usage:

let result = with_reservation(&token, 4000, |_reservation| {
    let response = call_llm(prompt, max_tokens: 4000);
    (response.tokens_used as u64, response)
});

5. Manual Reserve / Commit

For finer control, use reserve and commit directly:

match token.reserve(100) {
    Ok(reservation) => {
        let result = do_work();
        reservation.commit(result.actual_usage);
    }
    Err(e) => {
        log::warn!("Quota unavailable: {e}");
    }
}

Dropping a Reservation without calling commit commits the full reserved amount.

6. Splitting Tokens for Agent-to-Agent RPC

Split a portion of your quota to pass to a child agent:

let child_token: QuotaToken = token.split(200);
let child_agent = SummarizerAgent::new_phantom().await;
let summary = child_agent.summarize(text, child_token).await;

The child agent receives the QuotaToken as a method parameter and uses it for its own reservations. Merge returned tokens back:

token.merge(returned_token);

QuotaToken implements IntoValue and FromValueAndType, so it can be passed as an agent method parameter.

7. Dynamic Resource Updates via CLI

Modify resource limits at runtime — changes affect running agents immediately:

golem resource update api-calls --limit '{"type":"rate","value":200,"period":"minute","max":2000}' --environment prod

Key Constraints

• Acquire QuotaToken once and reuse — do not create a new one per call
• split panics if child_expected_use exceeds the parent’s current expected-use
• merge panics if the tokens refer to different resources
• with_reservation returns Err(FailedReservation) only for reject enforcement — throttle suspends transparently
• Resource names in code must match the names in golem.yaml resourceDefaults