# Tutorial 2: Service Tasks

Call external services (microservices, HTTP APIs, GraphQL, RabbitMQ) from within a workflow. Handle failures and timeouts gracefully.

## Concepts Introduced

- `.Call()` — invoke a transport with payload and optional response capture
- Address types — `LegacyRabbit`, `Microservice`, `Http`, `Graphql`, `Rabbit`
- `resultKey` — store the service response in workflow state
- `whenFailure` / `whenTimeout` — recovery branches
- `WorkflowHandledBranchAction.Complete` — shorthand for "complete on error"
- `timeoutSeconds` — per-step timeout override (default: 1 hour)

## Key Points

- Each `Call` step executes synchronously within the workflow
- The per-step timeout wraps the entire call including transport-level retries
- Transport timeouts (30s default) control individual attempt duration
- If no failure/timeout handler is defined, the error propagates and the signal pump retries

## Variants

- [C# Fluent DSL](csharp/)
- [Canonical JSON](json/)

## Next

[Tutorial 3: Decisions](../03-decisions/) — branch workflow logic based on conditions.