Variable interpolation

When configuring a library function's parameters you can use dynamic data from the context or received events.

To do so, include a variable interpolation expression in a text field. A variable interpolation expression has the form: {SOURCE[PATH]}.

SOURCE may be one of:

  • event,
  • env, and
  • params.

event references the received event. env references the applications variables. params references a library function's parameters.

PATH is some expression that references a part of the SOURCE, e.g. .foo.

A complete variable interpolation expression can thus look like {}. This expression would expand to the foo property of the received event. One can also include an expression among other text, e.g. Request took {event.request.duration}s.

If an expression can't be resolved, the expression will be included as is. E.g. say that the event has no bar property. Then would the expression {} not be replaced.

env is always available.

params is only available within library functions.

event is only in a handler context, i.e. if a parameter with an event expression is used in the setup context, the resolution would fail as there is no event, and the expression would be used as is.