REST API

Overview

The REST API module connects DMAIC.io to external data sources. It performs HTTP GET requests against a URL, maps individual fields of the JSON response to columns in the worksheet, and can run on a schedule — e.g. to regularly pull measurements from a server, a machine controller, or a cloud service into the worksheet.

Endpoint: A saved entry with name, URL, optional HTTP headers, and a mapping table. Any number of endpoints can be managed per project — e.g. one per machine or per data source.

JSON path: A dot notation that addresses a specific value or array in the API response (e.g. data.measurements or result.values[*].temperature). The value behind this path is written to the assigned worksheet column.

Mapping (JSON path → column): A list of assignments: each entry maps one JSON path to one target column in the worksheet. On every fetch, values are written according to these mappings.

Write mode: Controls how fetched values are written to the columns — either replace (old values are overwritten) or append (new values are added at the bottom). Append is suitable for ongoing data capture.

Schedule: Optional repeating fetch in minutes or hours. As long as the module is open, it automatically calls the endpoint at the configured interval.

Operation

Setting up an endpoint

• Use "+" to create a new endpoint and give it a meaningful name.
• Enter the URL — typically a REST interface that returns JSON.
• Add HTTP headers if needed (e.g. Authorization for API keys or bearer tokens).
• Click the play button to run a test fetch — the response is displayed for inspection.
• Identify JSON paths in the response and assign each one to a worksheet column.
• Pick the write mode: replace or append.
• Optional: enable the schedule and enter an interval in minutes or hours.

Managing endpoints

• Endpoints can be duplicated — handy for several similar data sources.
• Deleting an endpoint automatically stops a running schedule.
• The full state (endpoints, mappings, schedules) is included in the project export.

Pitfalls

CORS errors: Browsers block cross-origin API calls by default unless the server sends the right CORS headers. Solution: enable CORS on the endpoint or use a proxy. Symptom: network error without a response body.

Sensitive data in headers: API keys, bearer tokens, and passwords are stored in clear text inside the project and included in exports. Check data before sharing or rotate tokens regularly.

Wrong JSON path: Typos or the wrong nesting depth cause empty columns to be written. Always run a test fetch and check the result before using the endpoint productively.

Write mode "replace" with a schedule: With "replace" enabled and a schedule running, the sheet content is overwritten on every fetch — old values are lost. For time series, choose "append".

Schedule only runs while the module is open: The recurring fetch runs in the browser tab. Closing the module or the browser stops the schedule. For real background acquisition, a server-side job is required.

Very short intervals: Intervals below one minute put a heavy load on the browser and the remote endpoint. For high-frequency data, buffer on the server side and fetch in larger steps.