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

[Gabriel Goller <g.goller@proxmox.com>]

>> > > <snip>
>> > >
>> > > 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?
>>
>> We currently have:
>>  1) journald (with stderr fallback)
>
>=> builder.journald_logging()
>
>(the fallback could just be implied, or do we ever not want that?)

true, I don't think we want to fail anywhere if there is no journald
anyway.

>>  2) stderr
>
>=> builder.stderr_logging()
>
>>  3) stderr (with pve formatting)
>
>=> builder.pve_logging() (#[cfg(feature = "pve")]?)

Maybe stderr_pve_logging? I'd like to mention 'stderr' somewhere in the
case we add some different pve-format logging (e.g. pve-tasklog).

>>  4) pbs tasklog
>^ I assume (4) is the "tasklog-or-journald" case?
>Not sure where (1) is really the right choice.
>
>Does (4) exist anywhere other than in the API daemons?
>
>=> builder.task_logging()
>
>(the journal-if-not-in-task part could be implied - or do we ever need
>to combine the tasklog part differently?)

Yes, in the proxmox-backup-manager. There we use stderr for all the
normal logs and the tasklogger for when we a task is started.

>> But the problem is we have different combinations and filters as well:
>> journald and stderr (perlmod), stderr and pbs tasklog (but only when we
>> are in a tasklog or when the level is error) (pbs-client), etc.
>
>^ Why is "pbs-client" the example here? IMO this sounds like the API
>daemons. The pbs-client *CLI* tool certainly should just log to stderr,
>and the "crate" otherwise doesn't decide this.

Oops, my bad I meant the proxmox-backup-manager.

>> The logging gets initiated in:
>
>(list below is reordered)
>
>>  * pbs proxy daemon
>>  * pbs api daemon
>
>^ API daemons - so those are case (4) - are they different from one
>another?

Nope, this is case 4. (To be exact case 1 + 4, journald + tasklog.)
Also you need to add filters here, this isn't just a "print everything
to journald", we only print to journald when the level is error or we
are *not* in a tasklog.

>>  * pbs proxmox-file-restore
>
>^ The VM side? Not sure what it needs, but seems special-enough to have
>its own code, unless we just log to the journal anyway

As far as I remember this one should print to stderr only. (This is
wrong in this patch.)

>>  * pbs tape pmt
>>  * pbs tape pmtx
>>  * pbs client
>>  * pbs pxar
>>  * pbs proxmox-backup-debug
>>  * pbs proxmox-backup-manager
>>  * pbs proxmox-backup-tape
>>  * pbs sg-tape-cmd
>
>^ IIRC all of these are CLI tools and should therefore all be case (2) -
>although I don't know about how the tape stuff works.
>If they do anything else, it would be good to know why and have this
>documented either in proxmox-log or in their logging-init functions.

All except the proxmox-backup-manager as far as I can see, because that
one starts pbs tasks directly.

>>  * pbs proxmox-daily-update
>
>The 'daily-update' may be a special case and could use the journal
>directly, but may as well be stderr->journald via its `.service`.
>But, yeah, obviously it would make actual tracing/debugging easier with
>a proper journald-logger here. So another user of case (1).

Agree.

>>  * perlmod
>^ For the lack of a better place (as pve, pmg and nftables code probably
>all want to share it), having this as a special function in proxmox-log
>makes some sense I suppose (but could be feature-guarded).

There is already a shared common::init_logger function in perlmod I think.

>> Exposing the builder directly without any helper functions would be fine
>> as well I reckon. The downside is that the initiation gets more
>> "complicated", e.g. (the pbs daemon):
>>
>>     LogBuilder::from_env("PBS_LOG", LevelFilter::INFO)
>>         .journald_on_no_tasklog_or_error()
>>         .tasklog().init()?;
>
>So yes this is probably okay to have, but I really don't think we need
>these huge names - like I said, it doesn't make sense to me that
>`.tasklog()` should be combined with anything other than this exact one
>other thing anyway, so the middle line there could just be left out IMO.

See above.
Also either we use a helper function which does everything for us (e.g.
init_perlmod_logger, init_journald_and_tasklog) or we use the builder
where we *need* to mention every layer separately. Otherwise you have different
builder functions, some which add a single layer and others that add
multiple layers + magic (which IMO is a mess).




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