fix: Avoid blocking on async runtime when resolving cloud scans

[Jesse-Bakker]

No description provided.

[evbo]

Not sure if it's related but on 0.46.0 I just tried scanning s3 lazily and it panicked with:

panicked at /usr/local/cargo/registry/src/index.crates.io-6f17d22bba15001f/polars-io-0.46.0/src/pl_async.rs:310:9:
can call blocking only when running on the multi-threaded runtime

example:

let s3_uri = format!("s3://{}/{}", bucket, key);
        let cloud_options = CloudOptions::default().with_aws(config_keys);
        let scan_args = ScanArgsParquet {
            cloud_options: Some(cloud_options),
            glob,
            ..ScanArgsParquet::default()
        };

        Ok(LazyFrame::scan_parquet(s3_uri, scan_args).unwrap())

[evbo]

full backtrace:

stack backtrace:
0: rust_begin_unwind
at /rustc/90b35a6239c3d8bdabc530a6a0816f7ff89a0aaf/library/std/src/panicking.rs:665:5
1: core::panicking::panic_fmt
at /rustc/90b35a6239c3d8bdabc530a6a0816f7ff89a0aaf/library/core/src/panicking.rs:74:14
2: core::panicking::panic_display
at /usr/local/rustup/toolchains/1.83.0-aarch64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/panicking.rs:264:5
3: tokio::runtime::scheduler::multi_thread::worker::block_in_place::panic_cold_display
at /usr/local/rustup/toolchains/1.83.0-aarch64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/panic.rs:100:13
4: tokio::runtime::scheduler::multi_thread::worker::block_in_place
at /usr/local/cargo/registry/src/index.crates.io-6f17d22bba15001f/tokio-1.41.1/src/runtime/scheduler/multi_thread/worker.rs:444:9
5: tokio::runtime::scheduler::block_in_place::block_in_place
at /usr/local/cargo/registry/src/index.crates.io-6f17d22bba15001f/tokio-1.41.1/src/runtime/scheduler/block_in_place.rs:20:5
6: tokio::task::blocking::block_in_place
at /usr/local/cargo/registry/src/index.crates.io-6f17d22bba15001f/tokio-1.41.1/src/task/blocking.rs:78:9
7: polars_io::pl_async::RuntimeManager::block_on_potential_spawn
at /usr/local/cargo/registry/src/index.crates.io-6f17d22bba15001f/polars-io-0.46.0/src/pl_async.rs:310:9
8: polars_io::path_utils::expand_paths_hive::{{closure}}
at /usr/local/cargo/registry/src/index.crates.io-6f17d22bba15001f/polars-io-0.46.0/src/path_utils/mod.rs:235:17
9: polars_io::path_utils::expand_paths_hive
at /usr/local/cargo/registry/src/index.crates.io-6f17d22bba15001f/polars-io-0.46.0/src/path_utils/mod.rs:330:25
10: polars_plan::plans::ir::scan_sources::ScanSources::expand_paths_with_hive_update
at /usr/local/cargo/registry/src/index.crates.io-6f17d22bba15001f/polars-plan-0.46.0/src/plans/ir/scan_sources.rs:121:56
11: polars_plan::plans::conversion::dsl_to_ir::to_alp_impl::{{closure}}
at /usr/local/cargo/registry/src/index.crates.io-6f17d22bba15001f/polars-plan-0.46.0/src/plans/conversion/dsl_to_ir.rs:166:64
12: stacker::maybe_grow
at /usr/local/cargo/registry/src/index.crates.io-6f17d22bba15001f/stacker-0.1.17/src/lib.rs:55:9
13: polars_plan::plans::conversion::dsl_to_ir::to_alp_impl
at /usr/local/cargo/registry/src/index.crates.io-6f17d22bba15001f/polars-plan-0.46.0/src/plans/conversion/dsl_to_ir.rs:129:1
14: polars_plan::plans::conversion::dsl_to_ir::to_alp
at /usr/local/cargo/registry/src/index.crates.io-6f17d22bba15001f/polars-plan-0.46.0/src/plans/conversion/dsl_to_ir.rs:81:11
15: polars_plan::plans::optimizer::optimize
at /usr/local/cargo/registry/src/index.crates.io-6f17d22bba15001f/polars-plan-0.46.0/src/plans/optimizer/mod.rs:84:22
16: polars_lazy::frame::LazyFrame::optimize_with_scratch
at /usr/local/cargo/registry/src/index.crates.io-6f17d22bba15001f/polars-lazy-0.46.0/src/frame/mod.rs:624:22
17: polars_lazy::frame::LazyFrame::prepare_collect_post_opt
at /usr/local/cargo/registry/src/index.crates.io-6f17d22bba15001f/polars-lazy-0.46.0/src/frame/mod.rs:679:13
18: polars_lazy::frame::LazyFrame::_collect_post_opt
at /usr/local/cargo/registry/src/index.crates.io-6f17d22bba15001f/polars-lazy-0.46.0/src/frame/mod.rs:700:49
19: polars_lazy::frame::LazyFrame::collect
at /usr/local/cargo/registry/src/index.crates.io-6f17d22bba15001f/polars-lazy-0.46.0/src/frame/mod.rs:747:9
21: <core::pin::Pin

as core::future::future::Future>::poll
at /usr/local/rustup/toolchains/1.83.0-aarch64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/future/future.rs:123:9
22: <core::pin::Pin

as core::future::future::Future>::poll
at /usr/local/rustup/toolchains/1.83.0-aarch64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/future/future.rs:123:9
23: tokio::runtime::scheduler::current_thread::CoreGuard::block_on::{{closure}}::{{closure}}::{{closure}}
at /usr/local/cargo/registry/src/index.crates.io-6f17d22bba15001f/tokio-1.41.1/src/runtime/scheduler/current_thread/mod.rs:729:57
24: tokio::runtime::coop::with_budget
at /usr/local/cargo/registry/src/index.crates.io-6f17d22bba15001f/tokio-1.41.1/src/runtime/coop.rs:107:5
25: tokio::runtime::coop::budget
at /usr/local/cargo/registry/src/index.crates.io-6f17d22bba15001f/tokio-1.41.1/src/runtime/coop.rs:73:5
26: tokio::runtime::scheduler::current_thread::CoreGuard::block_on::{{closure}}::{{closure}}
at /usr/local/cargo/registry/src/index.crates.io-6f17d22bba15001f/tokio-1.41.1/src/runtime/scheduler/current_thread/mod.rs:729:25
27: tokio::runtime::scheduler::current_thread::Context::enter
at /usr/local/cargo/registry/src/index.crates.io-6f17d22bba15001f/tokio-1.41.1/src/runtime/scheduler/current_thread/mod.rs:428:19
28: tokio::runtime::scheduler::current_thread::CoreGuard::block_on::{{closure}}
at /usr/local/cargo/registry/src/index.crates.io-6f17d22bba15001f/tokio-1.41.1/src/runtime/scheduler/current_thread/mod.rs:728:36
29: tokio::runtime::scheduler::current_thread::CoreGuard::enter::{{closure}}
at /usr/local/cargo/registry/src/index.crates.io-6f17d22bba15001f/tokio-1.41.1/src/runtime/scheduler/current_thread/mod.rs:807:68
30: tokio::runtime::context::scoped::Scoped::set
at /usr/local/cargo/registry/src/index.crates.io-6f17d22bba15001f/tokio-1.41.1/src/runtime/context/scoped.rs:40:9
31: tokio::runtime::context::set_scheduler::{{closure}}
at /usr/local/cargo/registry/src/index.crates.io-6f17d22bba15001f/tokio-1.41.1/src/runtime/context.rs:180:26
32: std::thread::local::LocalKey::try_with
at /usr/local/rustup/toolchains/1.83.0-aarch64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/thread/local.rs:283:12
33: std::thread::local::LocalKey::with
at /usr/local/rustup/toolchains/1.83.0-aarch64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/thread/local.rs:260:9
34: tokio::runtime::context::set_scheduler
at /usr/local/cargo/registry/src/index.crates.io-6f17d22bba15001f/tokio-1.41.1/src/runtime/context.rs:180:9
35: tokio::runtime::scheduler::current_thread::CoreGuard::enter
at /usr/local/cargo/registry/src/index.crates.io-6f17d22bba15001f/tokio-1.41.1/src/runtime/scheduler/current_thread/mod.rs:807:27
36: tokio::runtime::scheduler::current_thread::CoreGuard::block_on
at /usr/local/cargo/registry/src/index.crates.io-6f17d22bba15001f/tokio-1.41.1/src/runtime/scheduler/current_thread/mod.rs:716:19
37: tokio::runtime::scheduler::current_thread::CurrentThread::block_on::{{closure}}
at /usr/local/cargo/registry/src/index.crates.io-6f17d22bba15001f/tokio-1.41.1/src/runtime/scheduler/current_thread/mod.rs:196:28
38: tokio::runtime::context::runtime::enter_runtime
at /usr/local/cargo/registry/src/index.crates.io-6f17d22bba15001f/tokio-1.41.1/src/runtime/context/runtime.rs:65:16
39: tokio::runtime::scheduler::current_thread::CurrentThread::block_on
at /usr/local/cargo/registry/src/index.crates.io-6f17d22bba15001f/tokio-1.41.1/src/runtime/scheduler/current_thread/mod.rs:184:9
40: tokio::runtime::runtime::Runtime::block_on_inner
at /usr/local/cargo/registry/src/index.crates.io-6f17d22bba15001f/tokio-1.41.1/src/runtime/runtime.rs:368:47
41: tokio::runtime::runtime::Runtime::block_on
at /usr/local/cargo/registry/src/index.crates.io-6f17d22bba15001f/tokio-1.41.1/src/runtime/runtime.rs:342:13
at /usr/local/rustup/toolchains/1.83.0-aarch64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/ops/function.rs:250:5
45: core::ops::function::FnOnce::call_once
at /rustc/90b35a6239c3d8bdabc530a6a0816f7ff89a0aaf/library/core/src/ops/function.rs:250:5
note: Some details are omitted, run with RUST_BACKTRACE=full for a verbose backtrace.

[evbo]

@ritchie46 could this be an edge case not accounted for? The workaround is to instead:

let lf = tokio::task::spawn_blocking(|| {
        LazyFrame::scan_parquet(s3_uri, scan_args)
            .unwrap()
            .collect()
            .unwrap()
    })
    .await
    .unwrap().lazy();

But that's not great as it involves collect