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Telo Signals

1. Core Principles​

The Telo engine handles asynchronous communication for business logic and resource orchestration exclusively through Signals.

  • True Zero-Cost Abstraction: Signal routing is resolved purely during the DAG build phase. The engine connects listener nodes directly to emitter nodes via memory pointers. At runtime, there is zero string translation, zero event bus lookups, and zero envelope wrapping. The raw payload is passed directly.
  • Strict Encapsulation: Signals emitted by resources within a module are private by default.
  • Explicit Wiring: Business events use explicit point-to-point Signals to guarantee deterministic execution paths.
  • Static Routing: Signal wiring uses static Resource Paths. Common Expression Language (CEL) is reserved strictly for dynamic runtime payload evaluation.

2. Module Boundary & Translation (exports)​

To expose an internal resource signal to the outside world, a module must explicitly map it in its root-level exports block. This categorizes the public contract and provides a clean, domain-specific alias for consumers.

Syntax (users-module.yaml):

kind: Kernel.Module
metadata:
  name: users

# The explicit public contract of this module
exports:
  resources:
    AddUser: InsertUser
  signals:
    # Compile-time alias: maps "UserCreated" to the internal "Success" port
    UserCreated:
      ref: InsertUser.Success
      payload:
        isPremium: "${{ signal.data.role == 'premium' }}"
---
# Internal resource (private by default)
kind: Postgres.Query
metadata:
  name: InsertUser
config:
  sql: "INSERT INTO users..."

3. Signal Consumption & Direct Wiring​

Consumers subscribe to exported signals using the trigger property with a static Resource Path.

Because Telo does not wrap payloads in runtime envelopes, the CEL condition evaluates the raw data object emitted by the source resource directly.

Syntax (consumer-module.yaml):

kind: Kernel.Import
metadata:
  name: Users
source: example/users@1.0.0

---
kind: Worker.Listener
metadata:
  name: PremiumWelcomeEmail

# 1. Static Wiring (Graph Edge): The engine hardwires this to InsertUser's success port.
trigger: Users.UserCreated

# 2. Dynamic Evaluation (CEL): Evaluates the raw payload directly (no "signal.data" wrapper).
condition: "${{ signal.isPremium == true }}"
do:
  kind: Http.Call
  # ...