On error links

Start another neuron when a neuron fails, and pass it the error message, so someone hears about it or the work is retried.

An On error link starts another neuron when a neuron fails, and passes it the error message. Use it to tell someone that a run failed, for example by email or Telegram, or to try the work again another way. Without an On error link, nothing runs on failure and the error is only logged.

Add an On error link

1. On the neuron card, click the red On error dot on the right edge.
2. Click the receptor (the left edge) of the neuron that should handle the failure.

The handling neuron starts only if this neuron fails. To cancel before you click the second neuron, press Esc.

Set up the neuron that handles the error

The error message arrives as the handling neuron's Connection input. Set up that neuron to use it:

1. In its DO, write what to do with the error, for example "Write a short alert saying which step failed and why."
2. In its SEND, choose where the alert goes, such as Email or Telegram.

To pass the error message somewhere else, open the connection and link Error message to an input or a SEND field. See Connections.

See which neurons run on error

The On error box in a neuron's SEND tab shows how many neurons start if it fails (On error · starts a number of neurons) and lists them. Click Manage to open the connections window, where you can disconnect them. On the card, hover over the On error dot to see the same.

Common problems

Nothing happens when a neuron fails

A neuron with no On error link only logs the error. Add an On error link to a neuron that tells you about it.

The error-handling neuron runs every time

The connection was made from the transmitter, so it starts the child after the parent finishes. Disconnect it in the connections window, then click the parent's red On error dot and click the child's receptor.