[QGIS-Developer] How to deal with time delay in QgsProcessingAlgorithm?

[Nils Nolde]

Hi,

I'd like to extend the openrouteservice API client plugin with a 
processing provider, but I run into problems implementing an error catch 
for 'Query limit exceeded' which is usually set to 40 requests/min. I 
want the plugin to be able to continue requesting when it hits that 
limit, after waiting the appropriate amount of time.

Currently I'm doing the following:

- The request is made in a 'client' module. That client module is called 
by the processing algorithms (e.g. isochrones) whose input feature 
source can have more than 40 features and likely exceed the minutely limit

- When the limit is exceeded, the 'client' module catches the HTTP error 
and invokes a time.sleep() for (60 - seconds_since_first_request) 
seconds, and then continues requesting

That freezes QGIS obviously, which is not what I want.

Any idea how to deal with this? I have no idea how to delay Python 
execution without freezing the main application..

Many thanks

Nils