feat(infrastructure): use celery worker

backend/app/celery_app.py

@@ -0,0 +1,61 @@
+import os
+from celery import Celery
+
+# Reuse existing RabbitMQ configuration env vars with vhost and optional TLS support
+# If RABBITMQ_URL is provided, it takes precedence. Otherwise compose from parts.
+if os.getenv("RABBITMQ_URL"):
+    RABBITMQ_URL = os.getenv("RABBITMQ_URL")  # type: ignore
+else:
+    from urllib.parse import quote
+
+    username = os.getenv("RABBITMQ_USERNAME", "user")
+    password = os.getenv("RABBITMQ_PASSWORD", "bitnami123")
+    host = os.getenv("RABBITMQ_HOST", "localhost")
+    port = os.getenv("RABBITMQ_PORT", "5672")
+    vhost = os.getenv("RABBITMQ_VHOST", "/")
+    use_ssl = os.getenv("RABBITMQ_USE_SSL", "0").lower() in {"1", "true", "yes"}
+    scheme = "amqps" if use_ssl else "amqp"
+
+    # Kombu uses '//' to denote the default '/' vhost. For custom vhosts, URL-encode them.
+    if vhost in ("/", ""):
+        vhost_path = "/"  # will become '//' after concatenation below
+    else:
+        vhost_path = f"/{quote(vhost, safe='')}"
+
+    # Ensure we end up with e.g. amqp://user:pass@host:5672// (for '/')
+    RABBITMQ_URL = f"{scheme}://{username}:{password}@{host}:{port}{vhost_path}"
+    if vhost in ("/", "") and not RABBITMQ_URL.endswith("//"):
+        RABBITMQ_URL += "/"
+
+# Default queue name to keep parity with the previous worker
+DEFAULT_QUEUE = os.getenv("MAIL_QUEUE", "mail_queue")
+
+# Use RPC backend by default to avoid coupling to Redis
+CELERY_BACKEND = os.getenv("CELERY_BACKEND", "rpc://")
+
+celery_app = Celery(
+    "app",
+    broker=RABBITMQ_URL,
+    backend=CELERY_BACKEND,
+    include=[
+        "app.workers.celery_tasks",
+    ],
+)
+
+# Ensure this Celery app becomes the default for producers (e.g., FastAPI process)
+# so that @shared_task.delay(...) uses the same broker/credentials as the worker.
+celery_app.set_default()
+
+# Basic, safe defaults – single prefetch helps fairness similarly to the old worker
+celery_app.conf.update(
+    task_default_queue=DEFAULT_QUEUE,
+    task_acks_late=True,
+    worker_prefetch_multiplier=int(os.getenv("CELERY_PREFETCH", "1")),
+    task_serializer="json",
+    result_serializer="json",
+    accept_content=["json"],
+    broker_heartbeat=0,  # let kombu handle heartbeats robustly in some envs
+)
+
+# Expose a shortcut for Celery CLI discovery: `celery -A app.celery_app worker ...`
+__all__ = ["celery_app"]