[BUG] Do not leak tokio tasks in the log service.

[rescrv]

Description of changes

The background tasks of wal3 were leaked because the log service was not
calling shutdown when dropping a log. This PR corrects that.

Test plan

Local benchmark. Will upload graph to GitHub PR.

Documentation Changes

N/A

[propel-code-bot]

This PR ensures that background Tokio tasks spawned by the wal3 log service are properly terminated by implementing a Drop handler for LogWriter, which now calls the shutdown method on the inner writer upon dropping. This prevents resource leakage when a log is closed or dropped.

This summary was automatically generated by @propel-code-bot

[github-actions]

Reviewer Checklist

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Testing, Bugs, Errors, Logs, Documentation

• Can you think of any use case in which the code does not behave as intended? Have they been tested?
• Can you think of any inputs or external events that could break the code? Is user input validated and safe? Have they been tested?
• If appropriate, are there adequate property based tests?
• If appropriate, are there adequate unit tests?
• Should any logging, debugging, tracing information be added or removed?
• Are error messages user-friendly?
• Have all documentation changes needed been made?
• Have all non-obvious changes been commented?

System Compatibility

• Are there any potential impacts on other parts of the system or backward compatibility?
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Quality

• Is this code of a unexpectedly high quality (Readability, Modularity, Intuitiveness)

[propel-code-bot]

[CompanyBestPractice]

Consider using parking_lot::Mutex instead of std::sync::Mutex in the LogWriter::drop implementation. Our company guideline states that parking_lot provides faster, more efficient implementations of synchronization primitives.

Suggested change

	let mut inner = self.inner.lock().unwrap();
	if let Some(writer) = inner.writer.as_mut() {
	let mut inner = self.inner.lock();
	if let Some(writer) = inner.writer.as_mut() {
	writer.shutdown();
	}

⚡ Committable suggestion

Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation.

[rescrv]

In this graph we plot the number of tokio tasks over time. Then we write to 10k collections. Notice that the tasks do not level off in the before, but do level off in the after.