log: introduce a shareable LogContext struct

Since hyper can spawn() more tasks, when we stop passing `WorkerTask`
references down the stack, we still need to be able to *inherit* the
current logging context. Hyper provides a way to replace its used
`spawn()` method, so we need to provide a way to reuse the logging
context.

Instead of having the `FileLogger` and warn counter separately
available with local-only access, put them behind an Arc<Mutex<>>.
Previously they already *were* behind an Arc<Mutex<>> as part of the
WorkerTaskState.

Signed-off-by: Wolfgang Bumiller <w.bumiller@proxmox.com>

proxmox-log/src/lib.rs

@@ -1,11 +1,11 @@
 #![cfg_attr(docsrs, feature(doc_cfg, doc_auto_cfg))]
 #![deny(unsafe_op_in_unsafe_fn)]
 
-use std::{
-    cell::{Cell, RefCell},
-    env,
-};
+use std::env;
+use std::future::Future;
+use std::sync::{Arc, Mutex};
 
+use tokio::task::futures::TaskLocalFuture;
 use tracing::Level;
 use tracing_log::{AsLog, LogTracer};
 use tracing_subscriber::filter::{filter_fn, LevelFilter};
@@ -34,8 +34,7 @@ pub use tracing::warn;
 pub use tracing::warn_span;
 
 tokio::task_local! {
-    pub static LOGGER: RefCell<FileLogger>;
-    pub static WARN_COUNTER: Cell<u64>;
+    static LOG_CONTEXT: LogContext;
 }
 
 pub fn init_logger(
@@ -55,7 +54,7 @@ pub fn init_logger(
                 .expect("Unable to open syslog")
                 .with_filter(log_level)
                 .with_filter(filter_fn(|metadata| {
-                    LOGGER.try_with(|_| {}).is_err() || *metadata.level() == Level::ERROR
+                    LogContext::exists() || *metadata.level() == Level::ERROR
                 })),
         )
         .with(TasklogLayer {}.with_filter(log_level));
@@ -64,3 +63,66 @@ pub fn init_logger(
     LogTracer::init_with_filter(log_level.as_log())?;
     Ok(())
 }
+
+/// A file logger and warnings counter which can be used across a scope for separate logging.
+/// Mainly used for worker-task logging.
+pub struct FileLogState {
+    pub warn_count: u64,
+    pub logger: FileLogger,
+}
+
+impl FileLogState {
+    fn new(logger: FileLogger) -> Self {
+        Self {
+            warn_count: 0,
+            logger,
+        }
+    }
+}
+
+/// A log context can be set for a sync or asynchronous scope to cause log messages to be added to
+/// a [`FileLogger`].
+#[derive(Clone)]
+pub struct LogContext {
+    logger: Arc<Mutex<FileLogState>>,
+}
+
+impl LogContext {
+    /// Create a logging context for a [`FileLogger`].
+    pub fn new(logger: FileLogger) -> Self {
+        Self {
+            logger: Arc::new(Mutex::new(FileLogState::new(logger))),
+        }
+    }
+
+    /// Check to see if a log context exists without getting a strong reference to it.
+    pub fn exists() -> bool {
+        LOG_CONTEXT.try_with(|_| ()).is_ok()
+    }
+
+    /// Get the current logging context if set.
+    pub fn current() -> Option<Self> {
+        LOG_CONTEXT.try_with(|ctx| ctx.clone()).ok()
+    }
+
+    /// Run a task with a new logger and an initial warn counter of zero.
+    pub fn sync_scope<F, R>(self, func: F) -> R
+    where
+        F: FnOnce() -> R,
+    {
+        LOG_CONTEXT.sync_scope(self, func)
+    }
+
+    /// Run a task with a new logger and an initial warn counter of zero.
+    pub fn scope<F>(self, f: F) -> TaskLocalFuture<Self, F>
+    where
+        F: Future,
+    {
+        LOG_CONTEXT.scope(self, f)
+    }
+
+    /// Access the internal state.
+    pub fn state(&self) -> &Arc<Mutex<FileLogState>> {
+        &self.logger
+    }
+}

proxmox-log/src/tasklog_layer.rs

@@ -8,34 +8,31 @@ use tracing::Subscriber;
 use tracing_subscriber::layer::Context;
 use tracing_subscriber::Layer;
 
-use crate::FileLogger;
-use crate::LOGGER;
-use crate::WARN_COUNTER;
+use crate::{FileLogState, LogContext};
 
 pub struct TasklogLayer;
 
 impl<S: Subscriber> Layer<S> for TasklogLayer {
     fn on_event(&self, event: &Event<'_>, _ctx: Context<'_, S>) {
-        let _result = LOGGER.try_with(|logger| {
+        if let Some(ctx) = LogContext::current() {
+            let mut logger = ctx.logger.lock().unwrap();
             let mut buf = String::new();
             event.record(&mut EventVisitor::new(&mut buf));
             let level = event.metadata().level();
-            log_to_file(&mut logger.borrow_mut(), level, &buf);
-        });
+            log_to_file(&mut logger, level, &buf);
+        }
     }
 }
 
-fn log_to_file(logger: &mut FileLogger, level: &Level, buf: &String) {
+fn log_to_file(logger: &mut FileLogState, level: &Level, buf: &String) {
     match *level {
         Level::ERROR | Level::WARN => {
-            WARN_COUNTER.with(|counter| {
-                counter.set(counter.get() + 1);
-            });
-            logger.log(buf);
+            logger.warn_count += 1;
+            logger.logger.log(buf);
         }
-        Level::INFO => logger.log(buf),
-        Level::DEBUG => logger.log(format!("DEBUG: {buf}")),
-        Level::TRACE => logger.log(format!("TRACE: {buf}")),
+        Level::INFO => logger.logger.log(buf),
+        Level::DEBUG => logger.logger.log(format!("DEBUG: {buf}")),
+        Level::TRACE => logger.logger.log(format!("TRACE: {buf}")),
     };
 }
 

proxmox-rest-server/src/worker_task.rs

@@ -1,4 +1,3 @@
-use std::cell::{Cell, RefCell};
 use std::collections::{HashMap, VecDeque};
 use std::fs::File;
 use std::io::{BufRead, BufReader, Read, Write};
@@ -20,7 +19,7 @@ use tokio::sync::oneshot;
 use tracing::{info, warn};
 
 use proxmox_lang::try_block;
-use proxmox_log::{FileLogOptions, FileLogger, LOGGER, WARN_COUNTER};
+use proxmox_log::{FileLogOptions, FileLogger, LogContext};
 use proxmox_schema::upid::UPID;
 use proxmox_sys::fs::{atomic_open_or_create_file, create_path, replace_file, CreateOptions};
 use proxmox_sys::linux::procfs;
@@ -885,15 +884,9 @@ impl WorkerTask {
         let upid_str = worker.upid.to_string();
         let f = f(worker.clone());
 
-        let logger = RefCell::new(logger);
-        let counter = Cell::new(0);
-        tokio::spawn(LOGGER.scope(logger, async move {
-            WARN_COUNTER
-                .scope(counter, async move {
+        tokio::spawn(LogContext::new(logger).scope(async move {
             let result = f.await;
             worker.log_result(&result);
-                })
-                .await;
         }));
 
         Ok(upid_str)
@@ -916,8 +909,7 @@ impl WorkerTask {
         let _child = std::thread::Builder::new()
             .name(upid_str.clone())
             .spawn(move || {
-                LOGGER.sync_scope(RefCell::new(logger), || {
-                    WARN_COUNTER.sync_scope(Cell::new(0), || {
+                LogContext::new(logger).sync_scope(|| {
                     let worker1 = worker.clone();
 
                     let result = match std::panic::catch_unwind(move || f(worker1)) {
@@ -931,14 +923,16 @@ impl WorkerTask {
                     worker.log_result(&result);
                 });
             });
-            });
 
         Ok(upid_str)
     }
 
     /// create state from self and a result
     pub fn create_state(&self, result: &Result<(), Error>) -> TaskState {
-        let warn_count = WARN_COUNTER.try_with(Cell::get).unwrap_or(0);
+        let warn_count = match LogContext::current() {
+            Some(ctx) => ctx.state().lock().unwrap().warn_count,
+            None => 0,
+        };
 
         let endtime = proxmox_time::epoch_i64();