---
title: "Execute Methods"
description: "Execute methods of the LumiScan apps - one write that returns when the operation is done, the two results to check, and where each app keeps the inputs, outputs and status of a method."
product: "LumiScan Keryx"
component: "lumiscan-keryx"
version: "1.0.0"
display_version: "1.0.0.7"
latest_version: true
language: "en"
url: "https://docs.hdvisionsystems.com/en/lumiscan-keryx/1.0.0/execute.html"
---

# Execute Methods – LumiScan Keryx

An execute method is for an operation that finishes within about 1 s. The client writes any value to the method’s `execute` node, and the write returns when the operation has finished. One write, no state to track.

## Calling a method

1. Write the method’s inputs. A method has no arguments of its own: its inputs are separate nodes.

2. Write to the method’s `execute` node, for example `hdvisionsystems/lumiscan-cam-driver/camera1/control/capture/execute`.

3. Check **both** results:

   a. **The result of the write: could the operation run at all?** A refused write is never queued. See [Results of a method call](https://docs.hdvisionsystems.com/en/lumiscan-keryx/1.0.0/status-codes.html#method-results).

   b. **The outcome: did the operation succeed?** Where to read it depends on the app, see below.

4. Read the outputs.

## Where the inputs, outputs and outcome are {#where}

| Apps | Nodes | A failed operation shows as |
| --- | --- | --- |
| Cam Driver, AI Object Matching, Calibration | `<module>/control/<function>/execute`; the module’s `input/…` and `output/…`, the same the handshake uses | `control/status/code` and `text`, while the write itself answers that it ran. **Always read the status after the write.** A refused write leaves the status as it was |
| Template Finder, Object Finder, Area Detector, Text Reader | `<module>/<method>/execute`, `<module>/<method>/input/…`, `<module>/<method>/output/result`, `output/status-code`, `output/status-text` | `<method>/output/status-code` and `status-text`, **and** the write fails with the matching result |
| DMC, QR, Aztec and Barcode Reader | `<app>/execute`, `<app>/input/…`, `<app>/output/results` | the write fails; the reason is in the application log |

The finders' `status-code` has its own values, see [Execution status of the finders](https://docs.hdvisionsystems.com/en/lumiscan-keryx/1.0.0/status-codes.html#execution-status).

The functions under `system/` of every app are methods of the second kind: `system/<function>/execute` with `input/…` and `output/status-code`, `status-text`. A function of the whole app in the newer layout is `system/control/<function>/execute`, for example `system/control/restart/execute`.

## When a method runs {#ready}

A method of the Cam Driver, AI Object Matching or Calibration checks the same `control/<function>/ready` signal its handshake uses, and is refused while it is `false`. Most functions depend on something that must happen first - a connected camera, a loaded network, an image to save. The app’s manual says when each `ready` is `true`.

When a method is refused, read its `ready` together with `control/status/code` and `status/text`: `ready` names the missing precondition, and the status text still carries the message of the fault that caused it.

## Timeouts {#timeouts}

Keep in mind that the caller is blocked until the method returns. On LumiScan Keryx a client gives up after 2 s by default; the OPC UA Connector waits up to 60 s for a method call. A function that can take longer is offered as a [handshake](https://docs.hdvisionsystems.com/en/lumiscan-keryx/1.0.0/handshake.html) only.

## One operation at a time {#busy}

A module runs one operation at a time. A method called while another operation of the same module runs - an execute, a handshake, or in the finders a frame of a stream - is refused as busy (`TooManyOperations`, ctrlX `DL_TOO_MANY_OPERATIONS`). Retry it: the same call succeeds once the running operation has finished.

An operation that collides with a running stream is refused differently: the Cam Driver’s `capture` and AI Object Matching’s `inference` are not ready while their stream runs (`InvalidOperationMode`, ctrlX `DL_INVALID_OPERATION_MODE`). Retrying does not help; stop the stream first, see [Streams](https://docs.hdvisionsystems.com/en/lumiscan-keryx/1.0.0/streams.html#collisions).