[pve-devel] [PATCH v3 1/2] log: add perlmod logger and custom formatter

[Gabriel Goller]

Add special logger for perlmod. This one will print everything to
stderr (which will end up in the tasklog) and the errors to journald.
This also includes a custom formatter so that the stderr output will
look like: "INFO: sample message".

Reported-by: Maximiliano Sandoval <m.sandoval at proxmox.com>
Reported-by: Lukas Wagner <l.wagner at proxmox.com>
Signed-off-by: Gabriel Goller <g.goller at proxmox.com>
---

I didn't include Lukas's T-b as I changed quite a lot on this 
patch.

 proxmox-log/src/lib.rs                | 39 +++++++++++++++++++++++++++
 proxmox-log/src/pve_task_formatter.rs | 31 +++++++++++++++++++++
 2 files changed, 70 insertions(+)
 create mode 100644 proxmox-log/src/pve_task_formatter.rs

diff --git a/proxmox-log/src/lib.rs b/proxmox-log/src/lib.rs
index 8c74e42b618d..a058eb26ec98 100644
--- a/proxmox-log/src/lib.rs
+++ b/proxmox-log/src/lib.rs
@@ -5,6 +5,7 @@ use std::env;
 use std::future::Future;
 use std::sync::{Arc, Mutex};
 
+use pve_task_formatter::PveTaskFormatter;
 use tokio::task::futures::TaskLocalFuture;
 use tracing_log::{AsLog, LogTracer};
 use tracing_subscriber::filter::filter_fn;
@@ -15,6 +16,7 @@ use tasklog_layer::TasklogLayer;
 mod file_logger;
 pub use file_logger::{FileLogOptions, FileLogger};
 
+mod pve_task_formatter;
 mod tasklog_layer;
 
 pub use tracing::debug;
@@ -191,3 +193,40 @@ pub fn init_cli_logger(
     LogTracer::init_with_filter(log_level.as_log())?;
     Ok(())
 }
+
+/// Initialize logger for perlmod
+///
+/// This logger will log everything to stderr (which will land in the tasklog
+/// with a custom format) and the errors to syslog as well.
+pub fn init_perlmod_logger(
+    env_var_name: &str,
+    default_log_level: LevelFilter,
+) -> Result<(), anyhow::Error> {
+    let mut log_level = default_log_level;
+    if let Ok(v) = env::var(env_var_name) {
+        match v.parse::<LevelFilter>() {
+            Ok(l) => {
+                log_level = l;
+            }
+            Err(e) => {
+                eprintln!("env variable {env_var_name} found, but parsing failed: {e:?}");
+            }
+        }
+    }
+    let stderr_layer = tracing_subscriber::fmt::layer()
+        .event_format(PveTaskFormatter {})
+        .with_writer(std::io::stderr);
+
+    let registry = tracing_subscriber::registry()
+        .with(
+            tracing_journald::layer()
+                .ok()
+                .with_filter(filter_fn(|metadata| *metadata.level() == Level::ERROR))
+                .with_filter(log_level),
+        )
+        .with(stderr_layer.with_filter(log_level));
+
+    tracing::subscriber::set_global_default(registry)?;
+    LogTracer::init_with_filter(log_level.as_log())?;
+    Ok(())
+}
diff --git a/proxmox-log/src/pve_task_formatter.rs b/proxmox-log/src/pve_task_formatter.rs
new file mode 100644
index 000000000000..e9866a4b0869
--- /dev/null
+++ b/proxmox-log/src/pve_task_formatter.rs
@@ -0,0 +1,31 @@
+use std::fmt;
+use tracing::{Event, Subscriber};
+use tracing_subscriber::field::VisitOutput;
+use tracing_subscriber::fmt::format::{DefaultVisitor, Writer};
+use tracing_subscriber::fmt::{FmtContext, FormatEvent, FormatFields};
+use tracing_subscriber::registry::LookupSpan;
+
+/// This custom formatter outputs logs as they are visible in the PVE task log.
+///
+/// e.g.: "DEBUG: sample message"
+pub struct PveTaskFormatter {}
+
+impl<C, N> FormatEvent<C, N> for PveTaskFormatter
+where
+    C: Subscriber + for<'a> LookupSpan<'a>,
+    N: for<'a> FormatFields<'a> + 'static,
+{
+    fn format_event(
+        &self,
+        _ctx: &FmtContext<'_, C, N>,
+        mut writer: Writer<'_>,
+        event: &Event<'_>,
+    ) -> fmt::Result {
+        write!(writer, "{}: ", event.metadata().level().as_str())?;
+
+        let mut v = DefaultVisitor::new(writer.by_ref(), true);
+        event.record(&mut v);
+        v.finish()?;
+        writer.write_char('\n')
+    }
+}
-- 
2.39.5