basic-errors

Overview ¶

This sample demonstrates error handling with the core/status package.

The pattern: classify a failure once, where its meaning is known, with status.Errorf and a sentinel (PublicErrorf when the message is safe to show a client); add context with fmt.Errorf and %w, which keeps the classification; branch with errors.Is, never on message text. At the HTTP boundary the status picks the response code, and only public messages reach the client.

• cookbookFlow produces classified errors and lets them propagate.
• improviseFlow consumes them, recovering from each with errors.Is.
• leakyFlow fails unclassified, so you can watch the boundary redact it.

Run it:

go run .

Or with the Dev UI, to call the flows from a browser and read a trace of every run at http://localhost:4000/traces:

curl -sL cli.genkit.dev | bash    # install the Genkit CLI, once
genkit start -- go run .

Or over HTTP, where the status becomes the response code:

# 400, public message: dish must not be empty.
curl -X POST http://localhost:8080/cookbookFlow \
  -H "Content-Type: application/json" -d '{"data": {"dish": ""}}'

# 404, public message: no recipe for "lasagna" in the cookbook.
curl -X POST http://localhost:8080/cookbookFlow \
  -H "Content-Type: application/json" -d '{"data": {"dish": "lasagna"}}'

# 200: the same miss, recovered from by improvising a recipe.
curl -X POST http://localhost:8080/improviseFlow \
  -H "Content-Type: application/json" -d '{"data": {"dish": "lasagna"}}'

# 500, generic message: the real text and its fake credentials stay in
# the server log and never reach the client.
curl -X POST http://localhost:8080/leakyFlow \
  -H "Content-Type: application/json" -d '{"data": null}'

Both recipe flows stream. Asking for the stream changes where a failure lands, since the response has answered 200 before the flow runs: the status and the public message arrive in the body rather than on the status line.

# 200, with {"error":{"status":"INVALID_ARGUMENT", ...}} in the stream.
curl -N -X POST 'http://localhost:8080/cookbookFlow?stream=true' \
  -H "Content-Type: application/json" -d '{"data": {"dish": ""}}'