appender: add fallback to file creation date

[kaffarell]

When using the linux-musl target for rust, the file creation time cannot be retrieved, as the current version does not support it yet ( This will be fixed with ¹). In the meantime, we parse the datetime from the filename and use that as a fallback.

Fixes: #2999

Footnotes

1. https://github.com/rust-lang/rust/pull/125692 ↩

[zerolfx]

You may need to handle the prefix and suffix before parsing the date (a reverse function of join_date).

tracing/tracing-appender/src/rolling.rs

Lines 551 to 569 in c6bedbe

	pub(crate) fn join_date(&self, date: &OffsetDateTime) -> String {
	let date = date
	.format(&self.date_format)
	.expect("Unable to format OffsetDateTime; this is a bug in tracing-appender");
	match (
	&self.rotation,
	&self.log_filename_prefix,
	&self.log_filename_suffix,
	) {
	(&Rotation::NEVER, Some(filename), None) => filename.to_string(),
	(&Rotation::NEVER, Some(filename), Some(suffix)) => format!("{}.{}", filename, suffix),
	(&Rotation::NEVER, None, Some(suffix)) => suffix.to_string(),
	(_, Some(filename), Some(suffix)) => format!("{}.{}.{}", filename, date, suffix),
	(_, Some(filename), None) => format!("{}.{}", filename, date),
	(_, None, Some(suffix)) => format!("{}.{}", date, suffix),
	(_, None, None) => date,
	}
	}

[kaffarell]

Oh, yeah, you're right. Thanks for the heads up, updated it now. Extracted the the datetime from the prefix/suffix, then converted to PrimitiveDateTime (because OffsetDateTime also takes a offset), then just assume it's utc (this is fine, because we also do this when writing AFAIK).

[zerolfx]

The prefix or suffix can also contain a dot.

[kaffarell]

Damn, forgot about that. Should work now!

[kaffarell]

Third time's the charm :)
LMK what you think now!

[zerolfx]

replacen can occur within a string. We must ensure they are strictly prefixes or suffixes.

[kaffarell]

What do you mean exactly, could you paste an example? If the logfile prefix given is not actually the prefix in the filename, we will get a wrong date string and the parsing will fail, but this is intended.

[mladedav]

I think you could have suffix 2024 and then files like prefix-2024-01-01-2024 will get turned into -01-01-2024.

[kaffarell]

Oof, right. I could reverse the suffix and the whole filename string and then search through? Like that I would always get the first substring from behind. AFAIK rust doesn't have a function to make it more convention ...

[mladedav]

Wouldn't strip_prefix and strip_suffix work instead of replacen?

[bnjbvr]

Hi! what's the status of this PR? Looks like it addressed all the review comments, is it getting blocked for some reason? We'd love to have this fix to avoid using a fork of tracing that includes it, in a downstream project of ours 🙏 Thanks for your work here!

[kaffarell]

@davidbarsky friendly ping :)