pool(Pool)or to thread_create/3 of the pool option is not present. If the dispatch module is used (see section 3.2), spawning is normally specified as an option to the http_handler/3 registration.
We recomment the use of thread pools. They allow registration of a set of threads using common characteristics, specify how many can be active and what to do if all threads are active. A typical application may define a small pool of threads with large stacks for computation intensive tasks, and a large pool of threads with small stacks to serve media. The declaration could be the one below, allowing for max 3 concurrent solvers and a maximum backlog of 5 and 30 tasks creating image thumbnails.
:- use_module(library(thread_pool)). :- thread_pool_create(compute, 3, [ local(20000), global(100000), trail(50000), backlog(5) ]). :- thread_pool_create(media, 30, [ local(100), global(100), trail(100), backlog(100) ]). :- http_handler('/solve', solve, [spawn(compute)]). :- http_handler('/thumbnail', thumbnail, [spawn(media)]).