fix: panicking when can't create runtime for block_on

[bartlomieju]

No description provided.

[bartlomieju]

@ry after thorough reading of #2243 I can tell that the issue describes several different problems.

1. panic and hang when "Too many open files" occurs during creation of new Tokio runtime for block_on method - this PR addresses it
2. panics during execution of code inside block_on - this still isn't handled properly, basically Deno hans with message like:

thread 'tokio-runtime-worker-0' panicked at <some panic inside block_on>
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace.
thread '<unnamed>' panicked at 'called `Result::unwrap()` on an `Err` value: Canceled', src/libcore/result.rs:999:5
thread '<unnamed>' panicked at 'unexpected state while aborting task: Complete', /Users/biwanczuk/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-threadpool-0.1.15/src/task/mod.rs:216:21
s

I'd prefer to addresses second point in a separate PR as I need to think a bit more on how to test that properly.

I'm not sure there's a reliable reproduction to test issue resolved in this PR, we were just to eager creating runtimes ¯_(ツ)_/¯

[bartlomieju]

2. panics during execution of code inside block_on - this still isn't handled properly, basically Deno hans with message like:

Actually that might not be true, adding this test on master properly panics.

// cli/tokio_util.rs

#[cfg(test)]
mod tests {
  use super::*;
  use futures;

  #[test]
  #[allow(unreachable_code)]
  #[should_panic]
  fn test_block_on() {
    let fut = futures::future::lazy(|| {
      panic!("unexpected panic during block on");
      if false {
        return futures::future::err(());
      }
      futures::future::ok(1)
    });

    let r = block_on(fut);

    assert!(r.is_err());
  }
}

So I guess this should fix #2243 after all. There are of course other panics (most of them from unwraps I suppose) to be addressed but that's story for another big epic.

[ry]

This patch seems fine, but I'm not sure what it's fixing. #2243 seems to be fixed already....

[bartlomieju]

@ry this panic: #2243 (comment)

[ry]

@bartlomieju are you able to reproduce that panic on v0.17 ? I can’t.

[bartlomieju]

@ry:

v0.17.0

$ ulimit -n 44
$ RUST_BACKTRACE=full deno -r https://deno.land/std/testing/runner.ts
Download https://deno.land/std/testing/runner.ts
Compile https://deno.land/std/testing/runner.ts
thread '<unnamed>' panicked at 'called `Result::unwrap()` on an `Err` value: Os { code: 24, kind: Other, message: "Too many open files" }', src/libcore/result.rs:999:5
stack backtrace:
   0:        0x1083e7062 - std::panicking::take_hook::hb25650a43c7b4abc
   1:        0x1083e6d2b - std::panicking::take_hook::hb25650a43c7b4abc
   2:        0x1083e7850 - std::panicking::rust_panic_with_hook::h7d6a669f1a899680
   3:        0x1083e737d - std::panicking::begin_panic_fmt::h5340abefa09e06ca
   4:        0x1083e7269 - rust_begin_unwind
   5:        0x108412ac2 - core::panicking::panic_fmt::he11aece98ed722cd
   6:        0x109620ec3 - <arc_swap::Protection as core::convert::From<core::option::Option<&arc_swap::debt::Debt>>>::from::h427ca8060d312f50
   7:        0x1096f25e4 - <arc_swap::Protection as core::convert::From<core::option::Option<&arc_swap::debt::Debt>>>::from::h427ca8060d312f50
   8:        0x1095ef42f - <arc_swap::Protection as core::convert::From<core::option::Option<&arc_swap::debt::Debt>>>::from::h427ca8060d312f50
   9:        0x1095f3090 - <arc_swap::Protection as core::convert::From<core::option::Option<&arc_swap::debt::Debt>>>::from::h427ca8060d312f50
  10:        0x1083f6c4f - __rust_maybe_catch_panic
  11:        0x109601977 - <arc_swap::Protection as core::convert::From<core::option::Option<&arc_swap::debt::Debt>>>::from::h427ca8060d312f50
  12:        0x1083ca9be - __rust_alloc_zeroed
  13:        0x1083f5a9e - std::sys::unix::thread::Thread::new::h395dd3888e55e07a
  14:     0x7fff795cc2eb - _pthread_body
  15:     0x7fff795cf249 - _pthread_start
thread 'tokio-runtime-worker-1' panicked at 'called `Result::unwrap()` on an `Err` value: RecvError', src/libcore/result.rs:999:5
stack backtrace:
   0:        0x1083e7062 - std::panicking::take_hook::hb25650a43c7b4abc
   1:        0x1083e6d2b - std::panicking::take_hook::hb25650a43c7b4abc
   2:        0x1083e7850 - std::panicking::rust_panic_with_hook::h7d6a669f1a899680
   3:        0x1083e737d - std::panicking::begin_panic_fmt::h5340abefa09e06ca
   4:        0x1083e7269 - rust_begin_unwind
   5:        0x108412ac2 - core::panicking::panic_fmt::he11aece98ed722cd
   6:        0x1096214ac - <arc_swap::Protection as core::convert::From<core::option::Option<&arc_swap::debt::Debt>>>::from::h427ca8060d312f50
   7:        0x1096f3200 - <arc_swap::Protection as core::convert::From<core::option::Option<&arc_swap::debt::Debt>>>::from::h427ca8060d312f50
   8:        0x109692887 - <arc_swap::Protection as core::convert::From<core::option::Option<&arc_swap::debt::Debt>>>::from::h427ca8060d312f50
   9:        0x109696675 - <arc_swap::Protection as core::convert::From<core::option::Option<&arc_swap::debt::Debt>>>::from::h427ca8060d312f50
  10:        0x1096f4939 - <arc_swap::Protection as core::convert::From<core::option::Option<&arc_swap::debt::Debt>>>::from::h427ca8060d312f50
  11:        0x109083add - deno::isolate::Isolate::shared_isolate_handle::h757989c949f4c4f5
  12:        0x109029720 - core::task::wake::RawWaker::new::hb8bc634ea20c7569
  13:        0x1085dd43c - core::task::wake::RawWaker::new::hb8bc634ea20c7569
  14:        0x108585361 - core::task::wake::RawWaker::new::hb8bc634ea20c7569
  15:        0x108584a13 - core::task::wake::RawWaker::new::hb8bc634ea20c7569
fatal runtime error: failed to initiate panic, error 5
Abort trap: 6

this PR

$ ulimit -n 44
$ RUST_BACKTRACE=full deno_dev -r https://deno.land/std/testing/runner.ts
Download https://deno.land/std/testing/runner.ts
Compile https://deno.land/std/testing/runner.ts
error: Uncaught Other: Too many open files (os error 24)
► file:///Users/biwanczuk/dev/deno/js/dispatch_json.ts:40:11
    at DenoError (file:///Users/biwanczuk/dev/deno/js/errors.ts:20:5)
    at unwrapResponse (file:///Users/biwanczuk/dev/deno/js/dispatch_json.ts:40:11)
    at sendSync (file:///Users/biwanczuk/dev/deno/js/dispatch_json.ts:67:10)
    at fetchSourceFile (file:///Users/biwanczuk/dev/deno/js/compiler.ts:143:15)
    at _resolveModule (file:///Users/biwanczuk/dev/deno/js/compiler.ts:244:24)
    at getSourceFile (file:///Users/biwanczuk/dev/deno/js/compiler.ts:350:16)
    at findSourceFile (typescript.js:90560:29)
    at typescript.js:90459:85
    at getSourceFileFromReferenceWorker (typescript.js:90426:34)
    at processSourceFile (typescript.js:90459:13)

[ry]

Ok cool. thanks!

LGTM

[bartlomieju]

Just one small change - I replaced unwraps on one-shot channel with expects. If those calls fail then there are really too few available files to properly run compiler.