documentation in /transpara/docs

graph TD
    A[Start Application<br>File: main.py<br>Function: main] --> B{Validate Operation Mode<br>File: main.py<br>Class: OperationMode}
    B -->|Valid: ACTIVE or LOG_ONLY| C[Initialize Resources<br>File: main.py<br>Function: manage_resources]
    B -->|Valid: CONFIG| D[Log Config Mode and Exit<br>File: main.py]
    B -->|Invalid| E[Log Error and Exit<br>File: main.py]

    C --> F[Create OpcUaManager<br>File: opcua_client.py<br>Class: OpcUaManager]
    C --> G[Create OutputTStore<br>File: output_tstore.py<br>Class: OutputTStore]
    F --> H[Set OpcUaManager in AppState<br>File: state.py<br>Class: AppState]
    F --> I[Start OPC UA Client Task<br>File: opcua_client.py<br>Function: start_client]
    G --> J[Start TStore Send Data Loop<br>File: output_tstore.py<br>Function: send_data_loop]

    I --> K{Check Server Availability<br>File: opcua_client.py<br>Function: check_server_availability}
    K -->|Success| L{Connect to OPC UA Server<br>File: opcua_client.py<br>Function: ensure_connected}
    K -->|Failure| M{Retry Connection<br>connection_errors_count++}
    M -->|Max Retries Exceeded<br>connection_retry_count| N[Log Error and Exit<br>File: opcua_client.py]
    M -->|Retry| K

    L -->|Success| O[State: CONNECTED<br>connection_success_count++<br>File: opcua_client.py]
    L -->|Failure| M

    O --> P[Validate Nodes<br>File: opcua_client.py<br>Function: monitor_values]
    P --> Q{Check for Enumeration Nodes<br>File: opcua_client.py<br>Class: OpcUaEnumerationsManager}
    Q -->|Is Enumeration| R[Process Enum and Cache<br>File: opcua_client.py<br>Function: process_node_as_enum]
    Q -->|Not Enumeration| S[Subscribe to Nodes<br>File: opcua_client.py<br>Function: monitor_values]
    R --> S

    S -->|Success| T[State: Monitoring<br>consecutive_errors = 0<br>File: opcua_client.py]
    S -->|Failure| U{Retry Subscription<br>consecutive_errors++<br>File: opcua_client.py}
    U -->|force_reconnect=True or<br>consecutive_errors >= reconnect_error_threshold| K
    U -->|Retry<br>read_retry_count| S

    T --> V[Receive Data Changes<br>File: opcua_client.py<br>Class: SubscriptionHandler]
    V -->|LOG_ONLY| W[Log Data<br>File: opcua_client.py<br>Function: datachange_notification]
    V -->|ACTIVE| X[Enqueue Data to TStore<br>File: opcua_client.py<br>Function: datachange_notification]
    X --> J

    V -->|Connection Lost| Y[force_reconnect=True<br>consecutive_errors++<br>File: opcua_client.py]
    Y --> K

    subgraph Configuration Updates
        Z[Detect Config Update<br>File: main.py<br>Function: wait_for_config_update]
        Z -->|Config Changed| AA[Restart Resources<br>File: main.py<br>Function: manage_resources]
        AA --> C
    end

Loading

1. Start Application:

   • The app starts by running main.py, which initializes logging and validates the operation mode (OPERATION_MODE) from settings.

2. Validate Operation Mode:

   • Checks if the operation mode is valid (ACTIVE, LOG_ONLY, or CONFIG).
   • If invalid, logs an error and exits.
   • If CONFIG, logs configuration details and exits.
   • If ACTIVE or LOG_ONLY, proceeds to initialize resources.

3. Initialize Resources:

   • Creates an OutputTStore instance for data storage.
   • Creates an OpcUaManager instance with the OPC UA configuration from opcua_config.yaml.
   • Starts two background tasks:
     • OPC UA client task (opcua_manager.start_client) to connect and monitor nodes.
     • TStore send data loop (output_tstore.send_data_loop) to process enqueued data.

4. Connect to OPC UA Server:

   • Attempts to connect to the OPC UA server (endpoint from opcua_config.yaml).
   • Tracks connection state with state flag (Disconnected → Connected).
   • Increments connection_success_count on success or connection_errors_count on failure.
   • If connection fails, retries up to connection_retries times with exponential backoff.
   • If all retries fail, logs an error and exits.

5. Monitor Nodes:

   • Retrieves monitored items from opcua_config.yaml (e.g., node IDs like ns=1;i=1450).
   • Validates each node by reading its display name.
   • Creates a subscription with specified parameters (publishing_interval, queue_size, etc.).
   • Subscribes to each valid node, checking if it’s an enumeration node (using OpcUaEnumerationsManager).
   • Tracks subscription state with consecutive_errors counter and force_reconnect flag.

6. Handle Data Changes:

   • Receives data change notifications via SubscriptionHandler.
   • If LOG_ONLY mode, logs the data (value, timestamp, tags).
   • If ACTIVE mode, enqueues data to OutputTStore for storage.
   • Processes timestamps based on timestamp_source (gather, server, or source).

7. Handle Connection Issues:

   • If a connection error occurs (e.g., ConnectionError or bad status code), increments consecutive_errors.
   • If consecutive_errors reaches reconnect_error_threshold or specific OPC UA errors occur (e.g., BadSessionIDInvalid), sets force_reconnect=True.
   • Triggers reconnection by returning to the connection step.

8. Shutdown:

   • On interruption (e.g., KeyboardInterrupt) or error, cancels background tasks (opcua_task, tstore_task).
   • Disconnects the OPC UA client and logs shutdown completion.

---

Explanation of State Machine Elements

• Boolean Flags:

  • force_reconnect: Set to True when a session is invalid or consecutive_errors exceeds the threshold, triggering a reconnection attempt.
  • state: Tracks connection status (Disconnected or Connected), updated during connection attempts and disconnections.

• Counters:

  • connection_success_count: Increments on successful connections.
  • connection_errors_count: Increments on failed connection attempts.
  • consecutive_errors: Tracks sequential subscription failures, reset to 0 on success, and triggers reconnection if it reaches reconnect_error_threshold.
  • data_points_count: Tracks the number of data points processed (not fully utilized in the provided code but present for monitoring).

• Retries:

  • Connection retries (connection_retries): Attempts to connect to the OPC UA server with exponential backoff.
  • Subscription retries (read_retry_count): Attempts to subscribe to nodes, with a delay (read_retry_timeout) between tries.