feat: add cdr processing worker and dlq routing

.env.sample

@@ -23,6 +23,18 @@ KAFKA_DLQ_TOPIC_PARTITIONS=1
 KAFKA_DLQ_TOPIC_REPLICATION_FACTOR=1
 KAFKA_DLQ_TOPIC_RETENTION_MS=604800000
 
+
+# =========================
+# Processing Worker
+# =========================
+
+WORKER_INSTANCE_ID=worker-1
+
+KAFKA_AUTO_OFFSET_RESET=earliest
+KAFKA_CONSUMER_POLL_TIMEOUT_SECONDS=1
+
+KAFKA_DLQ_DELIVERY_TIMEOUT_SECONDS=5
+
 KAFKA_CONSUMER_GROUP=cdr-processing-workers
 
 

README.md

@@ -24,6 +24,12 @@ Validation
 Bounded Async Queue
     ↓
 Redpanda / cdr.raw
+    ↓
+Processing Worker
+    ↓
+Validation + Normalization
+    ├── valid → processed by worker
+    └── invalid → cdr.raw.dlq
 ```
 
 Infrastructure already available:
@@ -60,34 +66,67 @@ worker processing is not connected yet.
 * Kafka delivery acknowledgement before `202 Accepted`
 * `429 Too Many Requests` on ingestion queue saturation
 * `503 Service Unavailable` on Kafka delivery failure
+* Kafka consumer with manual offset management
+* Worker-side JSON decoding and validation
+* Worker-side CDR normalization
+* DLQ routing for malformed and unprocessable Kafka records
+* DLQ records with failure reason, failed field, timestamp, and worker instance
+* Kafka offsets committed only after the current processing outcome succeeds
 
 ## Project Structure
 
 ```text
-src/core/
+telecom-cdr-pipeline/
-├── config.py
+├── infrastructure/
+│   └── clickhouse/
+│       └── init.sql
 │
-├── api/
+├── scripts/
+│   ├── sample-valid-cdr.json
+│   └── sample-invalid-rat.json
+│
+├── src/
+│   └── core/
 │       ├── __init__.py
-│   ├── kafka_publisher.py
+│       ├── config.py
+│       │
+│       ├── api/
+│       │   ├── __init__.py
+│       │   ├── kafka_publisher.py
+│       │   ├── main.py
+│       │   ├── publisher.py
+│       │   └── routes.py
+│       │
+│       ├── domain/
+│       │   ├── __init__.py
+│       │   ├── errors.py
+│       │   ├── models.py
+│       │   ├── normalization.py
+│       │   └── validation.py
+│       │
+│       └── worker/
+│           ├── __init__.py
+│           ├── consumer.py
+│           ├── dlq.py
 │           ├── main.py
-│   ├── publisher.py
+│           └── processor.py
-│   └── routes.py
 │
-└── domain/
+├── tests/
-    ├── __init__.py
+│   ├── integration/
-    ├── errors.py
+│   │   └── test_ingestion_api.py
-    ├── models.py
+│   │
-    ├── normalization.py
+│   └── unit/
-    └── validation.py
+│       ├── test_dlq.py
-
+│       ├── test_normalization.py
-infrastructure/
+│       ├── test_project_setup.py
-└── clickhouse/
+│       ├── test_validation.py
-    └── init.sql
+│       └── test_worker_processor.py
-
+│
-tests/
+├── .env.example
-├── integration/
+├── .gitignore
-└── unit/
+├── docker-compose.yml
+├── pyproject.toml
+└── README.md
 ```
 
 ## Configuration

src/core/config.py

@@ -22,6 +22,14 @@ class Settings(BaseSettings):
     kafka_batch_size: int = 131_072
     kafka_producer_max_messages: int = 100_000
 
+    kafka_dlq_topic: str = "cdr.raw.dlq"
+    kafka_consumer_group: str = "cdr-processing-workers"
+    kafka_auto_offset_reset: str = "earliest"
+
+    kafka_consumer_poll_timeout_seconds: float = 1.0
+    kafka_dlq_delivery_timeout_seconds: float = 5.0
+
+    worker_instance_id: str = "worker-1"
 
 @lru_cache
 def get_settings() -> Settings:

src/core/worker/consumer.py

@@ -0,0 +1,215 @@
+import logging
+from typing import Any
+
+from confluent_kafka import Consumer, KafkaException, Message
+
+from core.config import Settings
+from core.domain.errors import (
+    CDRProcessingError,
+    FailureReason,
+)
+from core.worker.dlq import (
+    DLQPublishError,
+    DLQPublisher,
+)
+from core.worker.processor import (
+    decode_payload,
+    process_payload,
+)
+
+
+logger = logging.getLogger(__name__)
+
+
+class ProcessingWorker:
+    def __init__(
+        self,
+        settings: Settings,
+    ) -> None:
+        self._settings = settings
+
+        self._consumer = Consumer(
+            {
+                "bootstrap.servers":
+                    settings.kafka_bootstrap_servers,
+
+                "group.id":
+                    settings.kafka_consumer_group,
+
+                "client.id":
+                    settings.worker_instance_id,
+
+                "auto.offset.reset":
+                    settings.kafka_auto_offset_reset,
+
+                "enable.auto.commit": False,
+            }
+        )
+
+        self._dlq = DLQPublisher(settings)
+
+        self._running = False
+
+    def run(self) -> None:
+        self._running = True
+
+        self._consumer.subscribe(
+            [self._settings.kafka_raw_topic]
+        )
+
+        logger.info(
+            "Worker started. topic=%s group=%s instance=%s",
+            self._settings.kafka_raw_topic,
+            self._settings.kafka_consumer_group,
+            self._settings.worker_instance_id,
+        )
+
+        try:
+            while self._running:
+                message = self._consumer.poll(
+                    self._settings.kafka_consumer_poll_timeout_seconds
+                )
+
+                if message is None:
+                    continue
+
+                if message.error():
+                    logger.error(
+                        "Kafka consumer error: %s",
+                        message.error(),
+                    )
+                    continue
+
+                self._handle_message(message)
+
+        finally:
+            self._shutdown()
+
+    def _handle_message(
+        self,
+        message: Message,
+    ) -> None:
+        value = message.value() or b""
+
+        original_payload: Any = {
+            "raw": value.decode(
+                "utf-8",
+                errors="replace",
+            )
+        }
+
+        try:
+            payload = decode_payload(value)
+
+            original_payload = payload
+
+            normalized = process_payload(payload)
+
+        except CDRProcessingError as exc:
+            self._route_to_dlq(
+                message=message,
+                original_payload=original_payload,
+                error=exc,
+            )
+
+            return
+
+        except Exception as exc:
+            logger.exception(
+                "Unexpected CDR processing error."
+            )
+
+            error = CDRProcessingError(
+                reason=FailureReason.NORMALIZATION_ERROR,
+                detail=f"Unexpected processing error: {exc}",
+            )
+
+            self._route_to_dlq(
+                message=message,
+                original_payload=original_payload,
+                error=error,
+            )
+
+            return
+
+        logger.info(
+            (
+                "Normalized CDR. "
+                "raw_id=%s cdr_id=%s "
+                "service_type=%s rat=%s"
+            ),
+            normalized.raw_id,
+            normalized.cdr_id,
+            normalized.service_type,
+            normalized.radio_access_type,
+        )
+
+        # Temporary until ClickHouse batching is implemented.
+        self._commit(message)
+
+    def _route_to_dlq(
+        self,
+        message: Message,
+        original_payload: Any,
+        error: CDRProcessingError,
+    ) -> None:
+        logger.warning(
+            (
+                "Routing CDR to DLQ. "
+                "reason=%s field=%s "
+                "partition=%s offset=%s"
+            ),
+            error.reason.value,
+            error.failed_field,
+            message.partition(),
+            message.offset(),
+        )
+
+        try:
+            self._dlq.publish(
+                original_payload=original_payload,
+                error=error,
+            )
+
+        except DLQPublishError:
+            logger.exception(
+                "DLQ publishing failed. "
+                "Original Kafka offset will not be committed."
+            )
+
+            raise
+
+        self._commit(message)
+
+    def _commit(
+        self,
+        message: Message,
+    ) -> None:
+        committed = self._consumer.commit(
+            message=message,
+            asynchronous=False,
+        )
+
+        for partition in committed or []:
+            if partition.error is not None:
+                raise KafkaException(
+                    partition.error
+                )
+
+        logger.debug(
+            "Committed Kafka offset. partition=%s offset=%s",
+            message.partition(),
+            message.offset(),
+        )
+
+    def stop(self) -> None:
+        self._running = False
+
+    def _shutdown(self) -> None:
+        logger.info("Worker shutting down.")
+
+        try:
+            self._dlq.close()
+
+        finally:
+            self._consumer.close()

src/core/worker/dlq.py

@@ -0,0 +1,124 @@
+import json
+import time
+from datetime import datetime, timezone
+from typing import Any
+
+from confluent_kafka import KafkaException, Producer
+
+from core.config import Settings
+from core.domain.errors import CDRProcessingError
+
+
+class DLQPublishError(Exception):
+    pass
+
+
+def build_dlq_envelope(
+    original_payload: Any,
+    error: CDRProcessingError,
+    worker_instance: str,
+) -> dict[str, Any]:
+    return {
+        "original_payload": original_payload,
+        "failure_reason": error.reason.value,
+        "failed_field": error.failed_field,
+        "failed_at": (
+            datetime.now(timezone.utc)
+            .isoformat()
+            .replace("+00:00", "Z")
+        ),
+        "worker_instance": worker_instance,
+    }
+
+
+class DLQPublisher:
+    def __init__(
+        self,
+        settings: Settings,
+    ) -> None:
+        self._settings = settings
+
+        self._producer = Producer(
+            {
+                "bootstrap.servers":
+                    settings.kafka_bootstrap_servers,
+
+                "client.id":
+                    f"{settings.worker_instance_id}-dlq",
+
+                "acks": "all",
+                "enable.idempotence": True,
+
+                "compression.type": "lz4",
+
+                "message.timeout.ms":
+                    settings.kafka_message_timeout_ms,
+            }
+        )
+
+    def publish(
+        self,
+        original_payload: Any,
+        error: CDRProcessingError,
+    ) -> None:
+        envelope = build_dlq_envelope(
+            original_payload=original_payload,
+            error=error,
+            worker_instance=self._settings.worker_instance_id,
+        )
+
+        value = json.dumps(
+            envelope,
+            separators=(",", ":"),
+            ensure_ascii=False,
+        ).encode("utf-8")
+
+        delivered = False
+        delivery_error = None
+
+        def on_delivery(err, message) -> None:
+            nonlocal delivered
+            nonlocal delivery_error
+
+            delivery_error = err
+            delivered = True
+
+        try:
+            self._producer.produce(
+                topic=self._settings.kafka_dlq_topic,
+                value=value,
+                on_delivery=on_delivery,
+            )
+
+        except (BufferError, KafkaException) as exc:
+            raise DLQPublishError(
+                f"Unable to queue DLQ message: {exc}"
+            ) from exc
+
+        deadline = (
+            time.monotonic()
+            + self._settings.kafka_dlq_delivery_timeout_seconds
+        )
+
+        while not delivered:
+            self._producer.poll(0.1)
+
+            if time.monotonic() >= deadline:
+                raise DLQPublishError(
+                    "DLQ Kafka delivery timed out."
+                )
+
+        if delivery_error is not None:
+            raise DLQPublishError(
+                f"DLQ delivery failed: {delivery_error}"
+            )
+
+    def close(self) -> None:
+        remaining = self._producer.flush(
+            self._settings.kafka_dlq_delivery_timeout_seconds
+        )
+
+        if remaining > 0:
+            raise DLQPublishError(
+                f"{remaining} DLQ message(s) were not delivered."
+            )

src/core/worker/main.py

@@ -0,0 +1,51 @@
+import logging
+import signal
+
+from core.config import get_settings
+from core.worker.consumer import ProcessingWorker
+
+
+logging.basicConfig(
+    level=logging.INFO,
+    format=(
+        "%(asctime)s "
+        "%(levelname)s "
+        "%(name)s "
+        "%(message)s"
+    ),
+)
+
+
+def main() -> None:
+    settings = get_settings()
+
+    worker = ProcessingWorker(
+        settings=settings,
+    )
+
+    def handle_shutdown(
+        signum,
+        frame,
+    ) -> None:
+        logging.getLogger(__name__).info(
+            "Shutdown signal received: %s",
+            signum,
+        )
+
+        worker.stop()
+
+    signal.signal(
+        signal.SIGINT,
+        handle_shutdown,
+    )
+
+    signal.signal(
+        signal.SIGTERM,
+        handle_shutdown,
+    )
+
+    worker.run()
+
+
+if __name__ == "__main__":
+    main()

src/core/worker/processor.py

@@ -0,0 +1,38 @@
+import json
+from typing import Any
+
+from core.domain.errors import (
+    CDRProcessingError,
+    FailureReason,
+)
+from core.domain.models import NormalizedCDR
+from core.domain.normalization import normalize_cdr
+from core.domain.validation import parse_raw_cdr
+
+
+def decode_payload(value: bytes) -> dict[str, Any]:
+    try:
+        text = value.decode("utf-8")
+        payload = json.loads(text)
+
+    except (UnicodeDecodeError, json.JSONDecodeError) as exc:
+        raise CDRProcessingError(
+            reason=FailureReason.MALFORMED_JSON,
+            detail=f"Unable to decode Kafka message as JSON: {exc}",
+        ) from exc
+
+    if not isinstance(payload, dict):
+        raise CDRProcessingError(
+            reason=FailureReason.NORMALIZATION_ERROR,
+            detail="Kafka JSON payload must be an object.",
+        )
+
+    return payload
+
+
+def process_payload(
+    payload: dict[str, Any],
+) -> NormalizedCDR:
+    raw_cdr = parse_raw_cdr(payload)
+
+    return normalize_cdr(raw_cdr)

tests/unit/test_dlq.py

@@ -0,0 +1,36 @@
+from core.domain.errors import (
+    CDRProcessingError,
+    FailureReason,
+)
+from core.worker.dlq import build_dlq_envelope
+
+
+def test_build_dlq_envelope() -> None:
+    original = {
+        "raw_id": "raw-invalid-001",
+        "rat": 99,
+    }
+
+    error = CDRProcessingError(
+        reason=FailureReason.INVALID_RAT_VALUE,
+        detail="Unsupported RAT value: 99.",
+        failed_field="rat",
+    )
+
+    envelope = build_dlq_envelope(
+        original_payload=original,
+        error=error,
+        worker_instance="worker-test",
+    )
+
+    assert envelope["original_payload"] == original
+
+    assert (
+        envelope["failure_reason"]
+        == "invalid_rat_value"
+    )
+
+    assert envelope["failed_field"] == "rat"
+    assert envelope["worker_instance"] == "worker-test"
+
+    assert envelope["failed_at"].endswith("Z")

tests/unit/test_worker_processor.py

@@ -0,0 +1,78 @@
+import json
+
+import pytest
+
+from core.domain.errors import (
+    CDRProcessingError,
+    FailureReason,
+)
+from core.worker.processor import (
+    decode_payload,
+    process_payload,
+)
+
+
+def valid_payload() -> dict:
+    return {
+        "raw_id": "raw-worker-001",
+        "src_ip": "10.240.12.1",
+        "device_id": "310410998877665",
+        "caller_num": "0019875551234",
+        "svc": "4G_DATA",
+        "up_bytes": 100,
+        "down_bytes": 200,
+        "rat": 6,
+        "lac": "4021",
+        "ci": "8812",
+        "epoch_start": 1789900000,
+        "epoch_end": 1789900300,
+    }
+
+
+def test_decode_valid_json_object() -> None:
+    value = json.dumps(
+        valid_payload()
+    ).encode("utf-8")
+
+    payload = decode_payload(value)
+
+    assert payload == valid_payload()
+
+
+def test_malformed_json() -> None:
+    with pytest.raises(
+        CDRProcessingError
+    ) as exc_info:
+        decode_payload(
+            b'{"raw_id": invalid}'
+        )
+
+    assert (
+        exc_info.value.reason
+        == FailureReason.MALFORMED_JSON
+    )
+
+
+def test_json_array_is_rejected() -> None:
+    with pytest.raises(
+        CDRProcessingError
+    ) as exc_info:
+        decode_payload(
+            b'["not", "a", "cdr"]'
+        )
+
+    assert (
+        exc_info.value.reason
+        == FailureReason.NORMALIZATION_ERROR
+    )
+
+
+def test_worker_normalizes_valid_payload() -> None:
+    normalized = process_payload(
+        valid_payload()
+    )
+
+    assert normalized.raw_id == "raw-worker-001"
+    assert normalized.radio_access_type == "LTE_4G"
+    assert normalized.total_bytes == 300
+    assert normalized.duration_seconds == 300