HttpKit | HTTP kit , supporting expiration | HTTP library

routes (and thus defroutes) expects each argument to be a request handler function. A list of handlers is not a handler function; hence the error. Happily, there is a function to convert a list of handlers to a single handler: routes! Since it wants N separate arguments, rather than a single list, you will need apply as well. So:

Not sure about the root cause, but I was able to find a similar, minimal example and a workaround.

I created a simple project with lein new app demo, then replaced the code for core.clj with:

A Clojure atom is designed specifically so that in a multi-threaded program, there can be multiple threads executing swap! on a single atom, and if your program does this, those update functions f given to swap! can run simultaneously. The only part of swap! that is synchronized is a 'compare and swap' operation that effectively does:

• lock the atom's state
• check if its current value is identical? to the reference it contained before f began executing, and if it is, replace it with the new object returned by f.
• Unlock the atom's state".

The function f may take a long time to calculate a new value from the current one, but the critical section above is merely a pointer comparison, and if equal, a pointer assignment.

That is why the doc string for swap! says "Note that f may be called multiple times, and thus should be free of side effects."