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      Combine Data Node Configuration Guide

      The Combine Data Node is used to merge multiple JSON payloads into a single structured output. It supports holding and synchronizing data from multiple upstream sources, enabling correlation of values by device, timestamp, or other shared context.

      What It Does

      The node holds incoming data from one or more source node IDs, and when triggered by a new payload, it combines that data into a single output object. It supports optional backfilling, error handling, and per-UID application for device-specific logic.

       Step-by-Step: How to Configure the Combine Data Node

      1. Add the node

        • Drag the Combine Data Node from the Logic panel into the workflow canvas.

      2. Connect upstream sources

        • Connect each node whose payloads should be stored or merged. Ensure each input emits a valid JSON structure.

      3. Open configuration

        • Double-click the node to access configuration settings.

       Configuration Fields

      Field Requirement Description
      Node Name* Required Identifier for the node within the workflow.
      Hold Data from Node ID(s) Required List of Node IDs to retain data from for later combination.
      Append Received Payloads Optional When enabled, retains a list of all payloads rather than just the latest.
      Backfill Optional If enabled, combines the current payload with the most recent from each listed node, even if not all are received in the current cycle.
      Payload Combine Method Optional Strategy for how payloads are combined:
      – Combine Latest Received: merges the latest available values from listed sources.
      Error Handling Action* Required Defines what happens when one or more payloads are missing or invalid:
      – Continue – Add Error to JSON appends an error object in the output.
      Apply To* Required Defines the scope of application:
      – UID: performs merge logic per device.
       

      Output Behavior

      The output will be a single merged JSON object that includes:

      • The most recent payload (or list of payloads, if appending)

      • Keys from all configured source nodes

      • Optionally, an error field if configured and a source is unavailable or invalid

      Example:

      json
      CopyEdit
      {
      "source1": { "temperature": 23 },
      "source2": { "humidity": 58 },
      "error": { "source3": "No data received" }
      }

       Best Practices

      • Always specify Hold Data from Node ID(s) explicitly. Avoid combining from undefined sources.

      • Enable Backfill when combining asynchronous data sources that don’t emit simultaneously.

      • Use UID scoping (Apply To: UID) when building workflows that handle multiple devices in parallel.

      • Prefer Continue – Add Error to JSON over silent failure for better debugging and downstream traceability.

      • Validate upstream nodes to ensure compatible JSON structures.

      Common Use Cases

      • Combine telemetry from multiple sensors into a single output payload

      • Synchronize state between separate nodes (e.g., config + measurement)

      • Merge enriched data from separate processing stages

      • Correlate computed results with raw input in one unified structure

      FAQ

      Q: What happens if one node is missing a payload?

      A: If Backfill is enabled, the node uses the most recent value. If not, the merge is skipped or an error is included, depending on the error handling setting.

      Q: Can this be used to create time-aligned datasets?

      A: Only if the upstream payloads are aligned manually or through another synchronization node. The Combine Data node does not manage timestamp alignment inherently.

      Q: Does this node support array merging?

      A: Not directly. If multiple payloads contain arrays, ensure downstream logic is prepared to handle the combined structure.