Error Handling and Edge Cases in the Restaurant Booking n8n Workflow

Description and use

A restaurant booking form feeds data into an n8n workflow that writes to Google Sheets and sends Gmail confirmations. Missing required fields, mismatched labels, rapid resubmissions, network glitches, and Gmail rate limits can cause null entries, duplicates, and failed emails.

Problem

Missing or malformed data from a web form can cause null entries in Google Sheets or failed email confirmations, leading to unreliable restaurant bookings.

Outcome

The workflow automates booking capture and confirmation but exposes failure modes such as null entries, duplicate rows, network errors, and email rate limits that need manual or additional error handling.

Workflow

• Form Trigger – formTrigger: receives JSON payload from web form
• Set – Preprocess Form: maps form fields to Google Sheet columns
• Google Sheets – Insert Booking: writes booking row into spreadsheet
• Email – Send Confirmation: sends confirmation email via Gmail

Evidence

Form submissions missing required fields pass empty values downstream, potentially causing null entries in Google Sheets or blank email recipients, requiring form-side retries to guarantee complete data.

Source

The Set node maps form fields to sheet columns; mismatched labels or quick resubmissions can result in empty columns or duplicate rows unless external duplicate checks are implemented.

Source

Google Sheets writes booking data but fails silently on network errors or row limits without automatic retries, and Gmail confirmation sends fail on malformed addresses or API rate limits, logging errors and moving on without retrying.

Source