Read Shopify Function logs and use observability tools to debug a failing Function in production

In-depth guide

Steps

1. In the Shopify Partners dashboard navigate to your app, open the Functions section, and select the Function; the Logs tab streams recent invocations with input, output, and any runtime errors
2. Use `shopify app logs` CLI command if you prefer terminal output; it tails live Function execution events for your development store
3. For structured debugging add console.error or console.log calls inside the Function run entrypoint; these appear in the logs panel as stdout/stderr entries alongside the invocation record
4. Examine the logs for input query errors (complexity exceeded, missing fields) vs logic errors (wrong output shape, type mismatches) — they surface differently in the log entry
5. If the Function returns an empty result (no discounts applied) without an error, add a log statement at each conditional branch to identify which path was taken; then replay with a known input using `shopify app function run`
6. Check the Function's execution time in the log; Functions have a strict time budget (check current docs for the limit) — exceeding it causes a timeout failure visible in the logs