Basic inspector support

[piscisaureus]

Continuation of #2696.

[ry]

LGTM!

Thank you @mtharrison - sorry this took so long for us to get landed!

[bartlomieju]

🎉 this is awesome!

I tested it with these two commands:

$ target/debug/deno -A --debug https://deno.land/[email protected]/http/file_server.ts
Debugger listening on ws://127.0.0.1:9888/97690037-256e-4e27-add0-915ca5421e2f
Inspector frontend connected.

This one works, brilliantly.

But I can't get this one to work:

$ target/debug/deno --debug tools/deno_tcp.ts
Debugger listening on ws://127.0.0.1:9888/97690037-256e-4e27-add0-915ca5421e2f
Inspector frontend connected.
thread 'tokio-runtime-worker-0' panicked at 'error binding to 127.0.0.1:9888: error creating server listener: Address already in use (os error 48)', /Users/biwanczuk/.cargo/registry/src/github.com-1ecc6299db9ec823/warp-0.1.20/src/server.rs:206:27
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace.
Waiting for debugger to disconnect...
thread 'main' panicked at 'internal error: entered unreachable code', /Users/biwanczuk/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-0.1.22/src/runtime/threadpool/mod.rs:296:26
thread 'tokio-runtime-worker-3' 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

As soon as I click "Inspect" in devtools I get above error.

[piscisaureus]

@bartlomieju
There are many known issues with this patch.
We landed it to have a starting point to iterate on.

[ry]

Bert discovered a problem - there's a debugger thread that's running unconditionally (even when --debug isn't running). This is causing a little failure in tests/workers_startup_bench.ts but it's indicative of a bigger design problem. Fix isn't super easy - so this will take a bit more to land - and I should have been reviewing more carefully : )

[eugeneo]

I am not sure if this is applicable here, but there were similar concerns about a thread in Node - and we ended up having that “always on” thread anyways. In the Node that thread is handling a signal used to enable Inspector on a running instance if the Inspector was not enabled from the command line.

…

On Fri, Oct 4, 2019 at 5:56 PM Ryan Dahl ***@***.***> wrote: ***@***.**** requested changes on this pull request. Bert discovered a problem - there's a debugger thread that's running unconditionally (even when --debug isn't running). This is causing a little failure in tests/workers_startup_bench.ts but it's indicative of a bigger design problem. Fix isn't super easy - so this will take a bit more to land - and I should have been reviewing more carefully : ) — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#2991?email_source=notifications&email_token=AACGJLML7O3BDI3JLBG4DZLQM7Q4VA5CNFSM4IYRSU4KYY3PNVWWK3TUL52HS4DFWFIHK3DMKJSXC5LFON2FEZLWNFSXPKTDN5WW2ZLOORPWSZGOCG7Y5AI#pullrequestreview-297766529>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AACGJLP7YJRFYMUHZ65NO5DQM7Q4VANCNFSM4IYRSU4A> .

[ry]

Closing this because we are unable to get it green. We will try again soon.