Exposing blocking client to Python via PyO3 causes get request to hang indefinitely

[ChristopherRabotin]

Hi there,

I have a structure called MetaFile whose sole job is to download the provided URI and store it locally, using blocking in reqwest. It works great in Rust. I've also exposed it to Python using the superb PyO3 library. Here is the problem: when calling exactly the same function from Python, the call just hangs indefinitely.

The exact code I'm working with is here: https://github.com/nyx-space/anise/blob/7b9b0d926fcb331a256500b8ad0e586e0bda81c2/anise/src/almanac/meta.rs#L193 .

Here is the relevant Rust code:

                                        let client = reqwest::blocking::Client::builder()
                                            .connect_timeout(Duration::from_secs(30))
                                            .timeout(Duration::from_secs(30))
                                            .build()
                                            .unwrap();

                                        println!("built");

                                        match client.get(url.clone()).send() {
                                            Ok(resp) => {
                                                println!("resp");
                                                if resp.status().is_success() {
// ...

When called from Python, it blocks forever on the start of this match.

>>> MetaFile("http://google.com/robots.txt").process()
built

Any idea what could be happening here?

Thanks

[seanmonstar]

Sorry, I'm not sure what the problem is. The only thing I can think of is that Python's GIL can cause locks when multi-threading, but probably not in this case. Still, it's the only thing that comes to mind,

[ChristopherRabotin]

That was the issue indeed: PyO3/pyo3#3732 (comment) .