Sientia DataOps OPC Ingestor

A high-performance, scalable OPC UA data ingestion system designed for industrial data collection and real-time streaming. The OPC Ingestor provides enterprise-grade data acquisition from OPC UA servers with automatic load balancing, fault tolerance, and comprehensive monitoring.

Features

Core Functionality

• OPC UA Integration: Native support for OPC UA servers with secure and unsecured connections
• Automatic Load Balancing: Slot-based architecture for horizontal scaling across multiple instances
• Persistent Storage: MongoDB integration for historical data persistence
• Health Monitoring: Comprehensive Prometheus metrics and health checks
• Fault Tolerance: Automatic failover, reconnection, and error recovery

Advanced Capabilities

• Certificate-based Security: Support for X.509 certificates and private keys
• Dynamic Tag Management: Runtime configuration updates without service interruption
• Resource Coordination: Redis-based slot leasing and instance coordination
• Notification System: Integrated alerting and notification management
• Performance Optimization: Configurable polling intervals and data collection frequencies

Architecture

The OPC Ingestor uses a modular, manager-based architecture designed for scalability and fault tolerance:

┌────────────────────────────────────────────
│   Main App      │    │  IngestorManager │    │   OPC Manager   │
│                 │◄──►│                  │◄──►│                 │
│ - Signal Hand.  │    │ - Slot Mgmt      │    │ - Connections   │
│ - Metrics       │    │ - Load Balancing │    │ - Subscriptions │
│ - Lifecycle     │    │ - Coordination   │    │ - Data Handler  │
└─────────────────┘    └──────────────────┘    └─────────────────┘
                                │
                                ▼
                       ┌──────────────────┐    ┌─────────────────┐
                       │  ResourceManager │    │  DataManager    │
                       │                  │    │                 │
                       │ - Redis Coord.   │    │ - MongoDB Store │
                       │ - Slot Leasing   │    │ - Data Pipeline │
                       │ - Heartbeats     │    │                 │
                       └──────────────────┘    └─────────────────┘

Key Components

• Ingestor: Main application orchestrator managing the overall lifecycle
• IngestorManager: Coordinates slot allocation, OPC server management, and load balancing
• OPC Manager: Handles individual OPC UA server connections and tag subscriptions
• Data Manager: Manages data persistence (MongoDB)
• Resource Manager: Coordinates resource allocation and instance coordination via Redis

🚪 OPC Gateway (SIENTIAPDE-1972)

Alongside the passive ingestion pipeline above, this service also runs an OPC Gateway for on-demand and command-driven interactions with OPC UA servers:

• NATS write consumer: consumes write commands from opc.write (see NATS_WRITE_SUBJECT) and executes them against the target OPC server (ingestor/adapters/nats_consumer.py, ingestor/engines/write.py). See Write commands below.
• On-demand gRPC ReadTag: a gRPC server (ingestor/adapters/grpc_server.py, ingestor/proto/opc_gateway.proto) for synchronous, single-tag reads.
• Scheduled active reads: a polling read engine (ingestor/engines/active_read.py) for tags that need periodic reads outside the subscription pipeline; orchestrator-side wiring lands in SIENTIAPDE-1974.
• Certificate management: each OPC connector has its own client certificate (opc_certificates), named in the slot and downloaded from MinIO (ingestor/connection/certs.py) rather than shipped in the image.

See Gateway environment variables and the # OPC Gateway blocks in .env.example for the new environment variables.

Write commands (C2) and write_status (C3)

The Laborious publishes one command per tag (SIENTIAPDE-1975):

{"server_id": "1", "addr": "ns=2;s=Pred", "value": 1.25, "data_type": "float",
 "model_id": "2", "model_name": "sin-approx", "schema": "sientia_data",
 "table_name": "predictions", "timestamp": "2026-10-13T12:00:00-03:00"}

• Written DataValue (SIENTIAPDE-2202): the value, plus the prediction timestamp as SourceTimestamp and a Good StatusCode. Timestamp and quality can be turned off separately; the value is always written. Each flag is taken from the command (write_timestamp / write_quality) when present, else from the env (WRITE_TIMESTAMP / WRITE_QUALITY), else true. The envs apply to every server of the gateway (per-server config is a future SIENTIAPDE-2276 card).

• Server connection: the command carries only server_id. The connection is resolved by ServerConfigResolver (ingestor/connection/servers.py): the live pooled connection opened by the reads, else the connectors document (type: opc_ua, status: Active) joined with opc_certificates, with the orchestrator's rule for the read slots (ingestor/connection/certificates.py), in the slot format (url, security, certificate). Lookups are cached for 60 s. An unknown or incomplete server is a failed write (server_not_found).

• Outcome: UPDATE ... SET write_status on the prediction row (by timestamp + model_id), keeping the worst outcome: ok < error < session_bad, and pending/NULL are replaced by any answer, so the order of the answers does not matter. The gateway is the only one that updates the column: the Laborious inserts the row as pending (merged with its PI Web API outcome) and never records OPC outcomes. The UPDATE never raises; its outcome (updated, kept, row_not_found, invalid, error) is logged and counted in opc_write_status_update_total. The reason of a failed write is logged by WriteEngine.

• NATS connection: the first connection gives up after 5 s (it runs on the main loop: nats-py's defaults would block it for minutes while NATS is down); once connected, it reconnects forever. A connection closed for good is started again by GatewayRuntime.idle_sweep.

📋 Prerequisites

• Python 3.11+
• Redis server
• MongoDB server
• OPC UA servers for data collection

Note: External dependencies (Redis, MongoDB) must be available either through:

• Port forwarding from a Kubernetes cluster
• External Docker Compose setup
• Cloud-managed services
• Local installations

️ Installation

Local Development Setup

1. Clone the repository

   git clone <repository-url>
   cd sientia-dataops-opc-ingestor
   

2. Create virtual environment

   python3.11 -m venv venv
   source ./venv/bin/activate
   

3. Install dependencies

   pip install -r requirements.txt
   

4. Create environment configuration file

   cp .env.example .env
   # Edit .env with your connection details
   

5. Configure external dependencies

   You'll need to set up port forwarding or connections to external services. For example:

   # Port forwarding from Kubernetes cluster
   kubectl port-forward svc/redis-master 6379:6379
   kubectl port-forward svc/mongodb 27017:27017
   
   # Or connect to external Docker Compose
   # Ensure services are accessible on localhost with appropriate ports
   

6. Register the OPC UA client certificate (only if connecting to a secured OPC UA server)

   See OPC Client Certificate below.

Usage

Running the Ingestor

Use the provided script to run the application locally:

# Make script executable (first time only)
chmod +x run_local.sh

# Run the application
./run_local.sh

The script will:

• Activate the virtual environment
• Load environment variables from .env
• Start the ingestor application

Running Tests and Coverage

Use the provided script to run tests with coverage:

# Make script executable (first time only)
chmod +x run_coverage.sh

# Run tests with coverage
./run_coverage.sh

The script will:

• Activate the virtual environment
• Run pytest with coverage reporting
• Generate HTML coverage report
• Open the coverage report in your browser

Manual Test Execution

You can also run tests manually:

# Activate virtual environment
source ./venv/bin/activate

# Run all tests
pytest

# Run with coverage
pytest --cov=ingestor --cov-report=html

Populating Redis with OPC Configuration

1. Activate virtual environment

   source ./venv/bin/activate
   

2. Run the Redis feeder

   python simulator/redis-feeder.py
   

The feeder creates sample OPC tag configurations in Redis that the ingestor can discover and manage.

🔐 OPC Client Certificate

Each OPC connector has its own X.509 client certificate (SIENTIAPDE-1974): the connector's security.client_certificate_id points to an opc_certificates document (kind: client, status: active). The Orchestrator joins them and writes, for each server of the slot, its security (mode, policy) and its certificate:

"certificate": {
  "certificate_id": 1,
  "application_uri": "urn:sientia:opc-ingestor",
  "cert": {"bucket": "opc-certificates", "object_name": "client/sientia-platform/opc-ingestor-cert.pem"},
  "private_key": {"bucket": "opc-certificates", "object_name": "client/sientia-platform/opc-ingestor-key.pem"}
}

The certificate is never read from the repository or the image. On connect, the CertProvider (ingestor/connection/certs.py) downloads both objects from MinIO into CERT_CACHE_DIR/<certificate_id>/ (default /tmp/opc-certs), and caches them per certificate. When the slot names other objects for the same certificate (it was replaced), the server config changes, the connection is re-opened and the files are downloaded again. A failed secured connection also forces a new download.

• Security only with a certificate. With a certificate, the connection uses the slot's security.mode (Sign / SignAndEncrypt) and security.policy (Basic256Sha256, Aes128Sha256RsaOaep, Aes256Sha256RsaPss, Basic256, Basic128Rsa15); an unknown one fails the connection. Without a certificate (null), or with mode: None, it connects without security, and a server that requires a certificate refuses the connection (the error shows in the log and the connection metrics). There is no default certificate.
• The certificate's application_uri (its SAN URI) is sent as the client application URI (KEPServer rejects a mismatch with BadCertificateUriInvalid).
• The server must trust the certificate (e.g. KEPServer: OPC UA Configuration Manager → Trusted Clients → Trust, then restart its runtime).

MinIO is only contacted when a certificate is first needed (one client per bucket), so a MinIO outage only affects secured servers, which are retried on the next main-loop iteration.

🧪 Testing

Unit Tests

# Install pytest
pip install pytest

# Run tests
pytest

# Run with coverage
pip install pytest-cov
pytest --cov=ingestor

# Generate HTML coverage report
pytest --cov=ingestor --cov-report=html

Functional Tests

# Run functional tests
pytest tests/functional/

📊 Monitoring and Metrics

The OPC Ingestor exposes comprehensive Prometheus metrics for monitoring:

Application Metrics

• app_up: Application health status
• app_main_loop_total: Main loop execution count
• app_main_loop_duration_seconds: Loop execution time
• app_errors_total: Error count

OPC Server Metrics

• opc_connection_status: Server connection status
• opc_tags_subscribed_current: Number of subscribed tags
• opc_cycles_without_data: Data reception health
• opc_subscriptions_created_total: Subscription count

Resource Management Metrics

• ingestor_slots_managed_current: Slots managed by this instance
• ingestor_active_total: Total active ingestor instances
• redis_connection_status: Redis connection health

Data Processing Metrics

• ingestor_tag_written_count: Data write operations
• redis_operations_total: Redis operation count

OPC Gateway Metrics

• opc_write_total: Active write attempts (NATS-driven), by result
• opc_write_latency_seconds: Active write latency
• opc_write_status_by_model: Last write outcome per model (1 = ok, 0 = failed; label status)
• opc_write_status_update_total: write_status UPDATEs, by result (updated, kept, row_not_found, invalid, error)
• opc_active_read_total: Scheduled/on-demand read attempts, by result
• opc_error_by_type_total: OPC errors by type (connection, conversion, session, ...)

⚙️ Configuration

Environment Variables

Variable	Description	Default	Required
REDIS_HOST	Redis server hostname	localhost	Yes
REDIS_PORT	Redis server port	6379	Yes
REDIS_USERNAME	Redis username	None	No
REDIS_PASSWORD	Redis password	None	No
LEASE_TTL	Slot lease time-to-live (seconds)	10	No
HEARTBEAT_TTL	Heartbeat time-to-live (seconds)	20	No
HOSTNAME	Pod identifier	localhost	No
POLL_INTERVAL	Main loop polling interval (seconds)	5	No
MONGODB_URL	MongoDB server address	localhost:27017	Yes
MONGODB_DATABASE	MongoDB database name	sientia	No
MONGODB_USERNAME	MongoDB username	sientia	No
MONGODB_PASSWORD	MongoDB password	sientia	No
HTTP_METRICS_PORT	Prometheus metrics port	9090	No

Gateway environment variables

Read by GatewayConfig (ingestor/config.py). Booleans accept true/1/yes (case-insensitive); anything else is false.

Variable	Description	Default
NATS_URL	NATS server for write commands (C2)	nats://localhost:4222
NATS_WRITE_SUBJECT	Subject of the write commands	opc.write
NATS_QUEUE	Queue group shared by the gateway pods	gateway-writers
GRPC_ENABLED	Starts the on-demand ReadTag gRPC server	false
GRPC_PORT	gRPC server port	50051
CERT_CACHE_DIR	Local cache of the client certificates downloaded from MinIO	/tmp/opc-certs
WRITE_TIMESTAMP	Writes the prediction timestamp as SourceTimestamp when the command has no write_timestamp	true
WRITE_QUALITY	Writes a Good StatusCode when the command has no write_quality	true
WRITE_MIN_PAUSE_S	Minimum pause between two OPC writes (seconds)	0.0
IDLE_CONN_MAX_S	Idle time before an unpinned pool connection is closed (seconds)	300.0

WRITE_TIMESTAMP / WRITE_QUALITY are independent and apply to every OPC server of the gateway; the value is always written. See Write commands for the precedence (command → env → true). MinIO (MINIO_*) and Postgres (POSTGRES_*) settings are listed in .env.example.

OPC Server Configuration

OPC servers are configured by the Orchestrator through Redis, one key per slot (slot:opc_tags:<n>). The gateway reads the slot v2 structure (contract C1): one entry per address, with one names item per collection / tag name / model, so the same address can feed several models under different names. Each server carries its security and its certificate (null = no security, see OPC Client Certificate):

{
  "slot:opc_tags:1": {
    "server1": {
      "name": "server1",
      "server_id": "kepserver",
      "url": "opc.tcp://localhost:4841",
      "subscription_period_ms": 7500,
      "security": {"mode": "SignAndEncrypt", "policy": "Basic256Sha256"},
      "certificate": {
        "certificate_id": 1,
        "application_uri": "urn:sientia:opc-ingestor",
        "cert": {"bucket": "opc-certificates", "object_name": "client/sientia-platform/opc-ingestor-cert.pem"},
        "private_key": {"bucket": "opc-certificates", "object_name": "client/sientia-platform/opc-ingestor-key.pem"}
      },
      "tags": {
        "ns=2;i=2": {
          "frequency": "15000",
          "active_read": {"enabled": false},
          "names": [
            {"collection": "raw_scouter-opcua-orchestrated-pipeline", "tag_name": "Counter", "model_name": "m1", "model_id": "1"},
            {"collection": "raw_scouter-basic-sum-model", "tag_name": "Contador", "model_name": "m2", "model_id": "2"}
          ]
        }
      }
    }
  }
}

Only the slot v2 is accepted (ingestor/io/slots.py): a slot without security, a tag without names, or a name without collection, tag_name or model_id is rejected and notified (OPC_SLOT_CONFIG_ERROR_<slot>), and the last good config keeps being read. The gateway and the Orchestrator of SIENTIAPDE-1974 are deployed together.

🔧 Development

Project Structure

sientia-dataops-opc-ingestor/
├── ingestor/                 # Main application code
│   ├── managers/            # Component managers
│   │   ├── data_manager.py # Data persistence and export
│   │   ├── ingestor_manager.py # Main coordination
│   │   ├── resource_manager.py # Resource coordination
│   │   └── server_reader.py # OPC UA server reads (SubscriptionEngine + pool)
│   ├── app.py              # Main application entry point
│   ├── ingestor.py         # Core ingestor logic
│   └── metrics.py          # Prometheus metrics definitions
├── simulator/               # OPC simulation and testing tools
├── scripts/                 # Ops scripts (e2e seed)
├── tests/                   # Test suite
└── requirements.txt         # Python dependencies

Adding New Features

1. Follow the manager pattern for new components
2. Add comprehensive docstrings for all public methods
3. Include Prometheus metrics for monitoring
4. Add unit tests for new functionality
5. Update this README with new features and configuration

🐛 Troubleshooting

Common Issues

1. OPC Connection Failures

   • Verify server URLs and network connectivity
   • Check certificate paths and security settings
   • Review server logs for authentication issues

2. Redis Connection Issues

   • Verify Redis server is running and accessible
   • Check authentication credentials
   • Ensure proper network configuration

3. Performance Issues

   • Monitor Prometheus metrics for bottlenecks
   • Adjust polling intervals and lease TTLs
   • Review OPC server performance and network latency

Debug Mode

Enable debug logging by setting the log level in your environment:

export LOG_LEVEL=DEBUG

Performance Tuning

Key Parameters

• POLL_INTERVAL: Main loop frequency (lower = more responsive, higher = less CPU)
• LEASE_TTL: Slot lease duration (lower = faster failover, higher = more stable)
• HEARTBEAT_TTL: Instance health check frequency
• Tag frequency: OPC tag collection rate (Hz)

Scaling Considerations

• Horizontal Scaling: Deploy multiple ingestor instances for high availability
• Load Distribution: Use Redis-based slot allocation for automatic load balancing
• Resource Limits: Monitor CPU, memory, and network usage
• Database Performance: Optimize MongoDB indexes

🤝 Contributing

1. Fork the repository
2. Create a feature branch
3. Make your changes with comprehensive testing
4. Update documentation and docstrings
5. Submit a pull request

Code Quality Standards

• Follow PEP 8 style guidelines
• Include comprehensive docstrings for all public methods
• Maintain test coverage above 80%
• Use type hints where appropriate
• Follow the established architectural patterns

🆘 Support

For support and questions:

• Check the troubleshooting section above
• Review the metrics and logs for error patterns
• Open an issue in the project repository
• Contact the development team

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Note: This OPC Ingestor is designed for production use in industrial environments. Ensure proper security configuration and network isolation for production deployments.