Invoking functions

Three ways to hit a deployed function, in order of convenience.

1. From the UI (Try it out)

The function detail page has a Try it out card with a mini HTTP client. Set method, path, headers, body, click Send, see the response with status code, headers, and body preview.

Path prefix should match the function's route. For a route of /... (wildcard), anything works. For /api/..., use /api/whatever.

This path relays through the control plane, which then proxies to the pod.

2. Through the control plane API

curl -X POST "http://localhost:8080/api/v1/applications/$APP/functions/$FN/invoke" \
  -H 'content-type: application/json' \
  -d '{
    "method": "GET",
    "path": "/hello?name=world",
    "headers": { "user-agent": ["curl/8"] }
  }'

Response:

{
  "status": 200,
  "headers": {"content-type": ["text/plain"], "content-length": ["7"]},
  "body": "Hello, world!\n",
  "bodyIsBase64": false,
  "truncated": false,
  "durationMs": 4
}

• body is base64-encoded (bodyIsBase64: true) when the response isn't valid UTF-8 or its content-type isn't textual.
• truncated: true means the response body exceeded the 1 MiB cap (proxy.MaxResponseBody).
• durationMs is measured control-plane-side, not inside the function.

This is what the UI's Try it out uses. It works regardless of whether the function is exposed externally via Ingress.

3. Directly to the pod

Each Application gets a K8s Service. You can port-forward or hit it from another pod:

# From your laptop
kubectl -n spinup-functions port-forward svc/greeter 8080:80
curl http://localhost:8080/hello?name=world

# From inside the cluster
curl http://greeter.spinup-functions.svc.cluster.local/hello?name=world

The Application page's Invoke card shows the exact port-forward command for the current app.

Public routing

For external traffic, the Helm chart installs an Istio VirtualService that routes dnsName traffic to the Application:

GET https://spinup.example.com/fn/{app-name}/{fn-route-suffix}
   →  Istio Gateway
   →  VirtualService(spinup-functions.svc.cluster.local)
   →  SpinApp pod

Configure dnsName in Helm values, provision the TLS cert (cert-manager), and functions become publicly reachable at /fn/{app-name}/....

If you don't run Istio, disable it (istio.enabled=false) and add your own Ingress / Gateway API resources pointing at the Application Services in spinup-functions.

Timeouts and limits

• Request body: 1 MiB max (proxy.MaxRequestBody in the CP). Larger requests get a 413.
• Response body: 1 MiB max cap on the CP's captured buffer; excess is truncated (truncated: true in the response envelope).
• Concurrency per pod: bounded by Spin's own concurrency settings — check the Spin docs for the current defaults.

Debugging failed invocations

If the response is 502 invoke failed: or 503 service unavailable::

1. Check the pod is up: kubectl get pods -n spinup-functions
2. Read the pod logs: Runtime logs card on the function page, or kubectl logs -n spinup-functions deploy/{app-name}
3. Check readiness: kubectl get svc {app-name} -n spinup-functions -o wide — no endpoints means the pod isn't Ready yet