Reqwest hangs after a particular number of requests

[bellwether-softworks]

I'm running into application hangs after a fixed number of requests (count varies between machines, but seems fixed on each). In particular, it only seems to happen when I use block_on and resolves when using .await syntax, so I'm not clear on where to direct my efforts. I'm hoping maybe I'm just doing something wrong that somebody else can spot, and would appreciate any help.

The problem can be reproduced using the code in this gist. As indicated above, if I change lines 15 and 16 to use .await instead of block_on, the problem does not present (or at least, not within the 200 iterations I've provisioned for).

[seanmonstar]

Don't use block_on from futures. It will park the thread in a way that doesn't allow Tokio's IO driver to do anything. It's also possible the number you're see is Tokio's cooperative budget not being able to replenish.

[bellwether-softworks]

@seanmonstar thank you, this whole thing was apparently a big lack of understanding on my part about how to introduce async functionality into a previously synchronous project; this issue forced me to get to understand async runtimes a bit better, and switching from the use of futures to the tokio runtime was the fix.