Add support for gettid() to PatternEncoder

[cloneable]

Add {i} and {tid} to allow logging in particular the Linux
thread ID as returned by gettid(). This is very useful for
system-wide debugging und monitoring with consistent
thread/task IDs.

Fixes: #231

[cloneable]

Two build errors. I'll take a look later.

error[E0658]: `cfg(rustdoc)` is experimental and subject to change
  --> C:\Users\runneradmin\.cargo\registry\src\github.com-1ecc6299db9ec823\gettid-0.1.2\src\lib.rs:16:55
   |
16 | #[cfg(any(target_os = "linux", target_os = "android", rustdoc))]
   |                                                       ^^^^^^^
   |
   = note: for more information, see https://github.com/rust-lang/rust/issues/43781

error[E0433]: failed to resolve: use of undeclared crate or module `gettid`
  --> src/encode/mod.rs:33:34
   |
33 |     pub(crate) static TID: u64 = gettid::gettid()
   |                                  ^^^^^^ use of undeclared crate or module `gettid`

[estk]

The gettid crate seems to use the unstable compilation flag cfg(rustdoc). The issue is that we build for stable rust and unstable compilation flags are unavailable on the stable channel of rust. I don't love that the crate has no tests.

I found another crate which has a seemingly more complete impl. I also like that it leverages nix which is know to be high quality software. The downside of the palaver crate is it seems maintenance has lapsed, and latest version is an alpha release from 2020.

It's a little unclear what to do from here, maybe bug the palaver authors or steal their implementation and add a comment linking back to an issue requesting they stabilize their api, so when that happens we can just pull them in...

[cloneable]

I had some similar thoughts about gettid crate. I was thinking of asking the thread-id people if the would add gettid() to their crate. (I didn't know about palaver.) log4rs already depends on it and thread-id seems like a good place to add support. What do you think about this?

[estk]

@cloneable that sounds like a great plan. Lmk if there is anything I can do to help.

[cloneable]

So I looked at palaver and it seems like a well written library, but I agree that owners may have stopped caring. (The owner of the repo is still active elsewhere.) I like that they support more OSes (but not Redox), that they avoid phtread_self() and that their gettid() returns u64 whereas thread-id's get() returns usize for some weird reason.

In summary none of gettid, thread-id and palaver is a great choice, but I still prefer palaver's provided implementations of gettid(). I'll ask them about state of maintainership and stability.

[cloneable]

nix is failing to build in 1.40 due to missing support for const_fn. I understand 1.40 is required for something, but are you planning to move to a younger release soon? If not then palaver is out.

[estk]

So, im open to changing the 1.40 requirement, but my feeling is that we should have at least a year of rust compiler backward compatibility. We could open a PR for palaver to gate the const fns on rust versions with dtolnay's: rustversion. @alecmocatta do you plan on cutting a non-alpha 0.3 soon? Are you looking for a maintainer for the palaver crate?

[alecmocatta]

@estk Thanks for the tag. I don't have the bandwidth at the moment but I'd happily add you as palaver maintainer to do so.

[estk]

@alecmocatta that would be great, I'll work on a pr for palaver that will add compatibility for 1.40. Excellent crate btw.

[alecmocatta]

@estk Thanks, look forward to reviewing!

[estk]

@alecmocatta & @cloneable it actually looks like the problem is in nix and it is only in one line of a macro there. I'm going to see if its just that and if they are open to PR's on the subject. I'll keep this thread up to date on how I go.

[estk]

Ok @alecmocatta & @cloneable I think the world has moved on. MSRV is 1.46 in not only nix, but also the bitflags crate. I've bumped master to test on 1.46. @cloneable you'll need to rebase and should be good. Apologies for holding this up.

[cloneable]

Looks good now. Thank you both!