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|
//! A `tracing` [`Subscriber`] that uses the [`log`] crate as a backend for
//! formatting `tracing` spans and events.
//!
//! When a [`TraceLogger`] is set as the current subscriber, it will record
//! traces by emitting [`log::Record`]s that can be collected by a logger.
//!
//! **Note**: This API has been deprecated since version 0.1.1. In order to emit
//! `tracing` events as `log` records, the ["log" and "log-always" feature
//! flags][flags] on the `tracing` crate should be used instead.
//!
//! [`log`]: log
//! [`Subscriber`]: https://docs.rs/tracing/0.1.7/tracing/subscriber/trait.Subscriber.html
//! [`log::Record`]:log::Record
//! [flags]: https://docs.rs/tracing/latest/tracing/#crate-feature-flags
#![deprecated(
since = "0.1.1",
note = "use the `tracing` crate's \"log\" feature flag instead"
)]
use crate::AsLog;
use std::{
cell::RefCell,
collections::HashMap,
fmt::{self, Write},
sync::{
atomic::{AtomicUsize, Ordering},
Mutex,
},
};
use tracing_core::{
field,
span::{self, Id},
Event, Metadata, Subscriber,
};
/// A `tracing` [`Subscriber`] implementation that logs all recorded
/// trace events.
///
/// **Note**: This API has been deprecated since version 0.1.1. In order to emit
/// `tracing` events as `log` records, the ["log" and "log-always" feature
/// flags][flags] on the `tracing` crate should be used instead.
///
/// [`Subscriber`]: https://docs.rs/tracing/0.1.7/tracing/subscriber/trait.Subscriber.html
/// [flags]: https://docs.rs/tracing/latest/tracing/#crate-feature-flags
pub struct TraceLogger {
settings: Builder,
spans: Mutex<HashMap<Id, SpanLineBuilder>>,
next_id: AtomicUsize,
}
thread_local! {
static CURRENT: RefCell<Vec<Id>> = RefCell::new(Vec::new());
}
/// Configures and constructs a [`TraceLogger`].
///
#[derive(Debug)]
pub struct Builder {
log_span_closes: bool,
log_enters: bool,
log_exits: bool,
log_ids: bool,
parent_fields: bool,
log_parent: bool,
}
// ===== impl TraceLogger =====
impl TraceLogger {
/// Returns a new `TraceLogger` with the default configuration.
pub fn new() -> Self {
Self::builder().finish()
}
/// Returns a `Builder` for configuring a `TraceLogger`.
pub fn builder() -> Builder {
Default::default()
}
fn from_builder(settings: Builder) -> Self {
Self {
settings,
..Default::default()
}
}
fn next_id(&self) -> Id {
Id::from_u64(self.next_id.fetch_add(1, Ordering::SeqCst) as u64)
}
}
// ===== impl Builder =====
impl Builder {
/// Configures whether or not the [`TraceLogger`] being constructed will log
/// when a span closes.
///
pub fn with_span_closes(self, log_span_closes: bool) -> Self {
Self {
log_span_closes,
..self
}
}
/// Configures whether or not the [`TraceLogger`] being constructed will
/// include the fields of parent spans when formatting events.
///
pub fn with_parent_fields(self, parent_fields: bool) -> Self {
Self {
parent_fields,
..self
}
}
/// Configures whether or not the [`TraceLogger`] being constructed will log
/// when a span is entered.
///
/// If this is set to false, fields from the current span will still be
/// recorded as context, but the actual entry will not create a log record.
///
pub fn with_span_entry(self, log_enters: bool) -> Self {
Self { log_enters, ..self }
}
/// Configures whether or not the [`TraceLogger`] being constructed will log
/// when a span is exited.
///
pub fn with_span_exits(self, log_exits: bool) -> Self {
Self { log_exits, ..self }
}
/// Configures whether or not the [`TraceLogger`] being constructed will
/// include span IDs when formatting log output.
///
pub fn with_ids(self, log_ids: bool) -> Self {
Self { log_ids, ..self }
}
/// Configures whether or not the [`TraceLogger`] being constructed will
/// include the names of parent spans as context when formatting events.
///
pub fn with_parent_names(self, log_parent: bool) -> Self {
Self { log_parent, ..self }
}
/// Complete the builder, returning a configured [`TraceLogger`].
///
pub fn finish(self) -> TraceLogger {
TraceLogger::from_builder(self)
}
}
impl Default for Builder {
fn default() -> Self {
Builder {
log_span_closes: false,
parent_fields: true,
log_exits: false,
log_ids: false,
log_parent: true,
log_enters: false,
}
}
}
impl Default for TraceLogger {
fn default() -> Self {
TraceLogger {
settings: Default::default(),
spans: Default::default(),
next_id: AtomicUsize::new(1),
}
}
}
#[derive(Debug)]
struct SpanLineBuilder {
parent: Option<Id>,
ref_count: usize,
fields: String,
file: Option<String>,
line: Option<u32>,
module_path: Option<String>,
target: String,
level: log::Level,
name: &'static str,
}
impl SpanLineBuilder {
fn new(parent: Option<Id>, meta: &Metadata<'_>, fields: String) -> Self {
Self {
parent,
ref_count: 1,
fields,
file: meta.file().map(String::from),
line: meta.line(),
module_path: meta.module_path().map(String::from),
target: String::from(meta.target()),
level: meta.level().as_log(),
name: meta.name(),
}
}
fn log_meta(&self) -> log::Metadata<'_> {
log::MetadataBuilder::new()
.level(self.level)
.target(self.target.as_ref())
.build()
}
fn finish(self) {
let log_meta = self.log_meta();
let logger = log::logger();
if logger.enabled(&log_meta) {
logger.log(
&log::Record::builder()
.metadata(log_meta)
.target(self.target.as_ref())
.module_path(self.module_path.as_ref().map(String::as_ref))
.file(self.file.as_ref().map(String::as_ref))
.line(self.line)
.args(format_args!("close {}; {}", self.name, self.fields))
.build(),
);
}
}
}
impl field::Visit for SpanLineBuilder {
fn record_debug(&mut self, field: &field::Field, value: &dyn fmt::Debug) {
write!(self.fields, " {}={:?};", field.name(), value)
.expect("write to string should never fail")
}
}
impl Subscriber for TraceLogger {
fn enabled(&self, metadata: &Metadata<'_>) -> bool {
log::logger().enabled(&metadata.as_log())
}
fn new_span(&self, attrs: &span::Attributes<'_>) -> Id {
let id = self.next_id();
let mut spans = self.spans.lock().unwrap();
let mut fields = String::new();
let parent = self.current_id();
if self.settings.parent_fields {
let mut next_parent = parent.as_ref();
while let Some(parent) = next_parent.and_then(|p| spans.get(p)) {
write!(&mut fields, "{}", parent.fields).expect("write to string cannot fail");
next_parent = parent.parent.as_ref();
}
}
let mut span = SpanLineBuilder::new(parent, attrs.metadata(), fields);
attrs.record(&mut span);
spans.insert(id.clone(), span);
id
}
fn record(&self, span: &Id, values: &span::Record<'_>) {
let mut spans = self.spans.lock().unwrap();
if let Some(span) = spans.get_mut(span) {
values.record(span);
}
}
fn record_follows_from(&self, span: &Id, follows: &Id) {
// TODO: this should eventually track the relationship?
log::logger().log(
&log::Record::builder()
.level(log::Level::Trace)
.args(format_args!("span {:?} follows_from={:?};", span, follows))
.build(),
);
}
fn enter(&self, id: &Id) {
let _ = CURRENT.try_with(|current| {
let mut current = current.borrow_mut();
if current.contains(id) {
// Ignore duplicate enters.
return;
}
current.push(id.clone());
});
let spans = self.spans.lock().unwrap();
if self.settings.log_enters {
if let Some(span) = spans.get(id) {
let log_meta = span.log_meta();
let logger = log::logger();
if logger.enabled(&log_meta) {
let current_id = self.current_id();
let current_fields = current_id
.as_ref()
.and_then(|id| spans.get(id))
.map(|span| span.fields.as_ref())
.unwrap_or("");
if self.settings.log_ids {
logger.log(
&log::Record::builder()
.metadata(log_meta)
.target(span.target.as_ref())
.module_path(span.module_path.as_ref().map(String::as_ref))
.file(span.file.as_ref().map(String::as_ref))
.line(span.line)
.args(format_args!(
"enter {}; in={:?}; {}",
span.name, current_id, current_fields
))
.build(),
);
} else {
logger.log(
&log::Record::builder()
.metadata(log_meta)
.target(span.target.as_ref())
.module_path(span.module_path.as_ref().map(String::as_ref))
.file(span.file.as_ref().map(String::as_ref))
.line(span.line)
.args(format_args!("enter {}; {}", span.name, current_fields))
.build(),
);
}
}
}
}
}
fn exit(&self, id: &Id) {
let _ = CURRENT.try_with(|current| {
let mut current = current.borrow_mut();
if current.last() == Some(id) {
current.pop()
} else {
None
}
});
if self.settings.log_exits {
let spans = self.spans.lock().unwrap();
if let Some(span) = spans.get(id) {
let log_meta = span.log_meta();
let logger = log::logger();
if logger.enabled(&log_meta) {
logger.log(
&log::Record::builder()
.metadata(log_meta)
.target(span.target.as_ref())
.module_path(span.module_path.as_ref().map(String::as_ref))
.file(span.file.as_ref().map(String::as_ref))
.line(span.line)
.args(format_args!("exit {}", span.name))
.build(),
);
}
}
}
}
fn event(&self, event: &Event<'_>) {
let meta = event.metadata();
let log_meta = meta.as_log();
let logger = log::logger();
if logger.enabled(&log_meta) {
let spans = self.spans.lock().unwrap();
let current = self.current_id().and_then(|id| spans.get(&id));
let (current_fields, parent) = current
.map(|span| {
let fields = span.fields.as_ref();
let parent = if self.settings.log_parent {
Some(span.name)
} else {
None
};
(fields, parent)
})
.unwrap_or(("", None));
logger.log(
&log::Record::builder()
.metadata(log_meta)
.target(meta.target())
.module_path(meta.module_path().as_ref().cloned())
.file(meta.file().as_ref().cloned())
.line(meta.line())
.args(format_args!(
"{}{}{}{}",
parent.unwrap_or(""),
if parent.is_some() { ": " } else { "" },
LogEvent(event),
current_fields,
))
.build(),
);
}
}
fn clone_span(&self, id: &Id) -> Id {
let mut spans = self.spans.lock().unwrap();
if let Some(span) = spans.get_mut(id) {
span.ref_count += 1;
}
id.clone()
}
fn try_close(&self, id: Id) -> bool {
let mut spans = self.spans.lock().unwrap();
if spans.contains_key(&id) {
if spans.get(&id).unwrap().ref_count == 1 {
let span = spans.remove(&id).unwrap();
if self.settings.log_span_closes {
span.finish();
}
return true;
} else {
spans.get_mut(&id).unwrap().ref_count -= 1;
}
}
false
}
}
impl TraceLogger {
#[inline]
fn current_id(&self) -> Option<Id> {
CURRENT
.try_with(|current| current.borrow().last().map(|span| self.clone_span(span)))
.ok()?
}
}
struct LogEvent<'a>(&'a Event<'a>);
impl<'a> fmt::Display for LogEvent<'a> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
let mut has_logged = false;
let mut format_fields = |field: &field::Field, value: &dyn fmt::Debug| {
let name = field.name();
let leading = if has_logged { " " } else { "" };
// TODO: handle fmt error?
let _ = if name == "message" {
write!(f, "{}{:?};", leading, value)
} else {
write!(f, "{}{}={:?};", leading, name, value)
};
has_logged = true;
};
self.0.record(&mut format_fields);
Ok(())
}
}
impl fmt::Debug for TraceLogger {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("TraceLogger")
.field("settings", &self.settings)
.field("spans", &self.spans)
.field("current", &self.current_id())
.field("next_id", &self.next_id)
.finish()
}
}
|