Flush traces before dsc exits

[SteveL-MSFT]

PR Summary

There's a race condition where a trace may be received before it is written. This shows up in tracing tests which fail intermittently due to the expected trace not showing up.

Fix is to ensure that stderr and stdout is flushed and give async threads time before dsc process exits by having custom exit() function that drops the tracing guard which flushes and then also flush stdout/stderr.

Some syntax changes to be consistent removing the crate name with use statements.

[Copilot]

Pull request overview

This PR aims to reduce intermittent tracing/test failures by ensuring pending output is flushed and giving trace/log writers a brief window to complete before the dsc process terminates.

Changes:

• Introduces a custom util::exit(code) that flushes stdout/stderr and sleeps briefly before terminating the process.
• Updates dsc/src/main.rs to use the new exit() instead of std::process::exit.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 5 comments.

File	Description
dsc/src/util.rs	Adds a custom process-exit helper intended to improve trace/output reliability at shutdown.
dsc/src/main.rs	Switches the CLI entrypoint to call the new exit helper.

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[Copilot]

Pull request overview

This PR addresses intermittent tracing test failures by attempting to ensure pending stdout/stderr output is written before the dsc process terminates.

Changes:

• Introduces a custom util::exit() that flushes stdio and sleeps briefly before exiting.
• Switches main.rs to use the new util::exit() instead of std::process::exit.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 4 comments.

File	Description
dsc/src/util.rs	Adds a custom process exit helper that flushes stdio and delays before exiting.
dsc/src/main.rs	Routes process termination through the new util exit helper.

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[andyleejordan]

👀 Seems like a workaround more than a solution...is there no way to wait on the async threads (with a timeout too so we don't hang)?

[SteveL-MSFT]

It looks like I can call https://docs.rs/tokio/latest/tokio/runtime/struct.Runtime.html#method.shutdown_timeout

[SteveL-MSFT]

Actually, I can't use that outside of an async task running within the runtime. And it looks like tokio itself doesn't provide a way to wait tokio-rs/tokio#5369

So this workaround seems like the only approach

[SteveL-MSFT]

@andyleejordan any suggestions?

[SteveL-MSFT]

I take it back, it looks like a WorkerGuard flushes when dropped (https://docs.rs/tracing-appender/latest/tracing_appender/non_blocking/struct.WorkerGuard.html), so need to keep the guard and drop on exit.

[SteveL-MSFT]

Spent too much time on this. Using a guard doesn't work because we're also using Indicatif crate for writing progress bars which makes the guard not work. So I'm back to having a short delay to allow async traces to get written as Indicatif repo says they don't support their own guard yet.

[Copilot]

Pull request overview

This PR aims to make tracing output deterministic at process shutdown by introducing a custom exit() path that drops a stored tracing guard and flushes stdout/stderr before terminating, reducing intermittent tracing-test flakes.

Changes:

• Add a global TRACING_GUARD and store the tracing default guard during enable_tracing().
• Introduce util::exit(code) to drop the stored guard and flush stdout/stderr before std::process::exit.
• Update main.rs to use the new exit() and simplify some util::-qualified calls.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
dsc/src/util.rs	Adds global tracing guard storage and a custom exit() that drops the guard + flushes stdio.
dsc/src/main.rs	Switches to util::exit() and updates imports/qualifiers to match the new shutdown behavior.

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