Task Queue

Construya una API REST que encola tareas para procesamiento en background con persistencia en base de datos.

Resumen

Este tutorial crea una API de gestión de tareas demostrando:

Endpoints REST - POST tareas, GET resultados
Publicación en cola - Despacho asíncrono de trabajos
Consumidores de cola - Workers en background
Persistencia en base de datos - Almacenamiento SQLite
Migraciones - Proceso one-shot que termina

flowchart LR
    subgraph api["Servidor HTTP"]
        POST["/tasks POST"]
        GET["/tasks GET"]
    end

    subgraph queue["Cola"]
        Q[("cola de tareas")]
    end

    subgraph workers["Workers"]
        W1["Consumidor 1"]
        W2["Consumidor 2"]
    end

    subgraph storage["Almacenamiento"]
        DB[(SQLite)]
    end

    POST -->|publish| Q
    Q --> W1
    Q --> W2
    W1 -->|INSERT| DB
    W2 -->|INSERT| DB
    GET -->|SELECT| DB

Estructura del Proyecto

task-queue/
├── wippy.lock
└── src/
    ├── _index.yaml
    ├── migrate.lua
    ├── create_task.lua
    ├── list_tasks.lua
    └── process_task.lua

Definiciones de Entradas

Cree src/_index.yaml:

version: "1.0"
namespace: app

entries:
  # Base de datos SQLite
  - name: db
    kind: db.sql.sqlite
    file: "./data/tasks.db"
    lifecycle:
      auto_start: true

  # Driver de cola en memoria
  - name: queue_driver
    kind: queue.driver.memory
    lifecycle:
      auto_start: true

  # Cola de tareas
  - name: tasks_queue
    kind: queue.queue
    driver: app:queue_driver

  # Servidor HTTP
  - name: gateway
    kind: http.service
    addr: ":8080"
    lifecycle:
      auto_start: true

  # Router
  - name: router
    kind: http.router
    meta:
      server: app:gateway

  # Proceso de migración (ejecuta una vez, termina)
  - name: migrate
    kind: process.lua
    source: file://migrate.lua
    method: main
    modules:
      - sql
      - logger

  # Servicio de migración (auto-inicia, termina al éxito)
  - name: migrate-service
    kind: process.service
    process: app:migrate
    host: app:processes
    lifecycle:
      auto_start: true

  # Process host
  - name: processes
    kind: process.host
    lifecycle:
      auto_start: true

  # Manejadores de API
  - name: create_task
    kind: function.lua
    source: file://create_task.lua
    method: handler
    modules:
      - http
      - queue
      - uuid

  - name: list_tasks
    kind: function.lua
    source: file://list_tasks.lua
    method: handler
    modules:
      - http
      - sql

  # Worker de cola
  - name: process_task
    kind: function.lua
    source: file://process_task.lua
    method: main
    modules:
      - queue
      - sql
      - logger
      - time
      - json

  # Endpoints
  - name: create_task.endpoint
    kind: http.endpoint
    meta:
      router: app:router
    method: POST
    path: /tasks
    func: app:create_task

  - name: list_tasks.endpoint
    kind: http.endpoint
    meta:
      router: app:router
    method: GET
    path: /tasks
    func: app:list_tasks

  # Consumidor de cola
  - name: task_consumer
    kind: queue.consumer
    queue: app:tasks_queue
    func: app:process_task
    concurrency: 2
    prefetch: 5
    lifecycle:
      auto_start: true

Proceso de Migración

Cree src/migrate.lua:

local sql = require("sql")
local logger = require("logger")

local function main()
    local db, err = sql.get("app:db")
    if err then
        logger:error("failed to connect", {error = tostring(err)})
        return 1
    end

    local _, exec_err = db:execute([[
        CREATE TABLE IF NOT EXISTS tasks (
            id TEXT PRIMARY KEY,
            payload TEXT NOT NULL,
            status TEXT NOT NULL DEFAULT 'pending',
            result TEXT,
            created_at INTEGER NOT NULL,
            processed_at INTEGER
        )
    ]])

    db:release()

    if exec_err then
        logger:error("migration failed", {error = tostring(exec_err)})
        return 1
    end

    logger:info("migration complete")
    return 0
end

return { main = main }

Retornar 0 señala éxito. El supervisor no reiniciará un proceso que termina normalmente con código 0.

Endpoint Crear Tarea

Cree src/create_task.lua:

local http = require("http")
local queue = require("queue")
local uuid = require("uuid")

local function handler()
    local req, req_err = http.request()
    local res, res_err = http.response()

    if not req or not res then
        return nil, "failed to get HTTP context"
    end

    local body, parse_err = req:body_json()
    if parse_err then
        res:set_status(http.STATUS.BAD_REQUEST)
        res:write_json({error = "JSON inválido"})
        return
    end

    if not body.action then
        res:set_status(http.STATUS.BAD_REQUEST)
        res:write_json({error = "action requerido"})
        return
    end

    local task_id = uuid.v4()
    local task = {
        id = task_id,
        action = body.action,
        data = body.data or {},
        created_at = os.time()
    }

    local ok, err = queue.publish("app:tasks_queue", task)
    if err then
        res:set_status(http.STATUS.INTERNAL_SERVER_ERROR)
        res:write_json({error = "falló al encolar tarea"})
        return
    end

    res:set_status(http.STATUS.ACCEPTED)
    res:write_json({
        id = task_id,
        status = "queued"
    })
end

return { handler = handler }

Endpoint Listar Tareas

Cree src/list_tasks.lua:

local http = require("http")
local sql = require("sql")

local function handler()
    local req, req_err = http.request()
    local res, res_err = http.response()

    if not req or not res then
        return nil, "failed to get HTTP context"
    end

    local db, db_err = sql.get("app:db")
    if db_err then
        res:set_status(http.STATUS.INTERNAL_SERVER_ERROR)
        res:write_json({error = "base de datos no disponible"})
        return
    end

    local status_filter = req:query("status")

    local query = sql.builder.select("id", "payload", "status", "result", "created_at", "processed_at")
        :from("tasks")
        :order_by("created_at DESC")
        :limit(100)

    if status_filter then
        query = query:where({status = status_filter})
    end

    local rows, query_err = query:run_with(db):query()
    db:release()

    if query_err then
        res:set_status(http.STATUS.INTERNAL_SERVER_ERROR)
        res:write_json({error = "query falló"})
        return
    end

    res:set_status(http.STATUS.OK)
    res:write_json({
        tasks = rows,
        count = #rows
    })
end

return { handler = handler }

Worker de Cola

Cree src/process_task.lua:

local queue = require("queue")
local sql = require("sql")
local logger = require("logger")
local time = require("time")
local json = require("json")

local function main(task)
    local msg, msg_err = queue.message()
    if msg_err then
        logger:error("failed to get message", {error = tostring(msg_err)})
        return false
    end

    logger:info("processing task", {
        id = task.id,
        action = task.action
    })

    -- Simular trabajo
    time.sleep("100ms")

    -- Procesar basado en acción
    local result
    if task.action == "uppercase" then
        result = {output = string.upper(task.data.text or "")}
    elseif task.action == "sum" then
        local nums = task.data.numbers or {}
        local total = 0
        for _, n in ipairs(nums) do
            total = total + n
        end
        result = {output = total}
    else
        result = {output = "processed"}
    end

    -- Almacenar en base de datos
    local db, db_err = sql.get("app:db")
    if db_err then
        logger:error("database unavailable", {error = tostring(db_err)})
        return false
    end

    local insert = sql.builder.insert("tasks")
        :columns("id", "payload", "status", "result", "created_at", "processed_at")
        :values(
            task.id,
            json.encode(task),
            "completed",
            json.encode(result),
            task.created_at,
            os.time()
        )

    local _, exec_err = insert:run_with(db):exec()
    db:release()

    if exec_err then
        logger:error("failed to store result", {error = tostring(exec_err)})
        return false
    end

    logger:info("task completed", {id = task.id})
    return true
end

return { main = main }

Retornar `true` reconoce el mensaje. Retornar `false` causa que el mensaje sea reencolado o enviado a una cola de mensajes muertos.

Ejecutando el Servicio

Inicializar y ejecutar:

mkdir -p data
wippy init
wippy run

Probar la API:

# Crear una tarea
curl -X POST http://localhost:8080/tasks \
  -H "Content-Type: application/json" \
  -d '{"action": "uppercase", "data": {"text": "hello world"}}'

# Respuesta: {"id": "550e8400-...", "status": "queued"}

# Esperar un momento para procesamiento, luego listar tareas
curl http://localhost:8080/tasks

# Respuesta: {"tasks": [...], "count": 1}

# Filtrar por status
curl "http://localhost:8080/tasks?status=completed"

Flujo de Mensajes

POST /tasks recibe solicitud, genera UUID, publica a cola
Consumidor de cola toma mensaje (2 workers concurrentes)
Worker procesa tarea, escribe resultado a SQLite
GET /tasks lee tareas completadas desde base de datos

Conceptos Demostrados

Concepto	API	Descripción
Endpoints REST	`http.request()`, `http.response()`	Manejar solicitudes HTTP
Publicación en cola	`queue.publish(id, data)`	Enviar trabajos asíncronos
Consumo de cola	`queue.message()`	Acceder mensaje en handler
Consultas de base de datos	`sql.get()`, `db:query()`	Leer datos
Query builder	`sql.builder.insert()`	Construir SQL de forma segura
Migraciones	Proceso retornando 0	Tareas de configuración one-shot
Concurrencia	`concurrency: 2`	Workers paralelos

Siguientes Pasos

Módulo HTTP - Manejo de request/response
Módulo Queue - Operaciones de cola de mensajes
Módulo SQL - Acceso a base de datos
Consumidores de Cola - Configuración de colas