Re: [pbs-devel] [PATCH proxmox v2 1/4] log: rename/move init functions

[Wolfgang Bumiller <w.bumiller@proxmox.com>]

On Mon, Feb 17, 2025 at 02:08:03PM +0100, Gabriel Goller wrote:
> On 11.02.2025 10:28, Wolfgang Bumiller wrote:
> > On Tue, Feb 11, 2025 at 10:22:44AM +0100, Wolfgang Bumiller wrote:
> > > On Mon, Feb 10, 2025 at 05:42:35PM +0100, Gabriel Goller wrote:
> > > > On 10.02.2025 15:37, Wolfgang Bumiller wrote:
> > > > > On Mon, Dec 09, 2024 at 11:46:03AM +0100, Gabriel Goller wrote:
> > > > > > +/// Inits a new tracing logger that prints to stderr or tasklog with the logging level specified in the
> > > > > > +/// environment variable `env_var`.
> > > > > > +///
> > > > > > +/// This logger is task-aware, which means if we are in a PBS task, we will retrieve the task-file
> > > > > > +/// and write to it. We'll only write to stderr if we are not in a task. If `env_var` doesn't exist
> > > > > > +/// or can't be read, use the `default_log_level`. The output will be very plain: no ansi, no
> > > > > > +/// timestamp, no level, just the message and it's
> > > > > > +/// fields.
> > > > > > +pub fn stderr_or_tasklog(
> > > > > > +    env_var: &str,
> > > > > > +    default_log_level: LevelFilter,
> > > > > > +) -> Result<(), anyhow::Error> {
> > > > > > +    let log_level = get_env_variable(env_var, default_log_level);
> > > > > > +
> > > > > > +    let registry = tracing_subscriber::registry()
> > > > > > +        .with(
> > > > > > +            plain_stderr_layer()
> > > > > > +                .with_filter(filter_fn(|_metadata| !LogContext::exists()))
> > > > >
> > > > > ^ This condition misses the `Level::ERROR` comparison while being
> > > > > suggested as a replacement for `init_cli_logger` which had it (not
> > > > > visible in the patch context lines, but it's there).
> > > > > If this is done on purpose, please explain it in the commit message.
> > > >
> > > > Oops, yeah my bad, this should be
> > > >
> > > >     !LogContext::exists() || *metadata.level() == Level::ERROR
> > > >
> > > > What do you think about the rest of the patch? I tried to implement this
> > > > with a builder pattern as well, but it turned out to be quite tricky
> > > > moving the layers around so I just wrote a ton of functions with long
> > > > names :(
> > > 
> > > The rest seems fine.
> > > It does look like it should be mostly a builder-pattern thing (as it
> > > kind of already is, with the final 2 lines being a kind of `.apply()`,
> > > but with the names being showing their intended use, it's fine for an
> > > `init` module to have specific common setups like this (`init_cli_…`,
> > > `…with_pve_format`, etc.)
> > > 
> > > Perhaps the journal/tasklog one could be named "init_daemon_log" (or
> > > just have an alias under that name)...
> > 
> > Sorry, I was reading it backwards, we're getting rid of those names...
> > That just goes to show I didn't properly think about this... :-)
> > 
> > Now, first of all, having the "descriptive" names there makes sense.
> > With the `pve` specific function we then still have a rather specific
> > one.
> > Therefore, with a specific `init` module, it would IMO be fine to have
> > situation-specific names for common setups.
> > 
> > Unless we can actually come up with a builder-pattern variant.
> > Perhaps it would have to be the Layer type rather than the subscriber
> > we'd need to turn into a builder, while having its final "apply" create
> > the subscriber and register it and initialize the LogTracer.
> 
> I cooked up a simple builder type thingy to build layers:
> 
> 
>     struct LogBuilder {
>         global_log_level: LevelFilter,
>         layer: Vec<
>             Box<dyn tracing_subscriber::Layer<tracing_subscriber::Registry> + Send + Sync + 'static>,
>         >,
>     }
> 
> 
> And the implementation:
> 
>     impl LogBuilder {
>         pub fn from_env(env_var: &str, default_log_level: LevelFilter) -> LogBuilder {
>             let log_level = get_env_variable(env_var, default_log_level);
>             LogBuilder {
>                 global_log_level: log_level,
>                 layer: vec![],
>             }
>         }
> 
>         pub fn journald_or_stderr(mut self) -> LogBuilder {
>             self.layer.push(
>                 journald_or_stderr_layer()
>                     .with_filter(self.global_log_level)
>                     .boxed(),
>             );
>             self
>         }
> 
>         pub fn journald_or_stderr_on_logcontext_and_error(mut self) -> LogBuilder {
>             self.layer.push(
>                 journald_or_stderr_layer()
>                     .with_filter(filter_fn(|metadata| {
>                         !LogContext::exists() || *metadata.level() == Level::ERROR
>                     }))
>                     .with_filter(self.global_log_level)
>                     .boxed(),
>             );
>             self
>         }
> 
>         //...
> 
>         pub fn init(self) -> Result<(), anyhow::Error> {
>             let registry = tracing_subscriber::registry().with(self.layer);
>             tracing::subscriber::set_global_default(registry)?;
> 
>             LogTracer::init_with_filter(self.global_log_level.as_log())?;
>             Ok(())
>         }
>     }
> 
> We could place this in a new builder module and then have the
> product-specific functions (e.g. init_pve_log, init_perlmod_log,
> init_pbs_log, etc.) in the init module.
> 
> What do you think?

Hmmm...
Those names are a bit long, and still as specific as before, so I'm not
sure we win a lot either way.

I'm wondering - if we really have so many specific cases - do we really
need them implemented in this crate, rather than where they are used?
How many different types of logging layers do we have and where atm?


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