My webserver has to make calls to 3-4 web services. I was going to implement it in Node.js, but was considering gevent since I'm not a huge fan of callback code. I understand that green threads are similar in behavior to OS threads, and each thread will wait for a response from one web service before calling the next. Is this correct?
For example, if I'm calling web services A, B, C, D, each of which take 1 second, node would have completed all 4 in 1 second (due to parallel calls), but gevent would take 4 seconds (since it chains them one after the other).
The documentation for gevent specifically states that multiple jobs can run concurrently (http://www.gevent.org/intro.html#example). Since it uses LibUV under the hood and has a similar main event pump to nodejs, both approaches will be extremely similar but running in a different programming environment and syntax. Pick whatever flavor you prefer.
Basically, gevent subtasks will yield to each other when they encounter a blocking operation. I am no node expert, but I believe this is how node runs as well. A good example is here: http://sdiehl.github.io/gevent-tutorial/#synchronous-asynchronous-execution