tracing_tunnel/types.rs
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//! Types to carry tracing events over the WASM client-host boundary.
use serde::{Deserialize, Serialize};
use tracing_core::{Level, Metadata};
use core::hash::Hash;
#[cfg(feature = "std")]
use std::path;
use crate::{
alloc::{BTreeMap, Cow, String, Vec},
TracedValues,
};
/// ID of a tracing [`Metadata`] record as used in [`TracingEvent`]s.
pub type MetadataId = u64;
/// ID of a tracing span as used in [`TracingEvent`]s.
pub type RawSpanId = u64;
/// Tracing level defined in [`CallSiteData`].
///
/// This corresponds to [`Level`] from the `tracing-core` library, but is (de)serializable.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, Serialize, Deserialize)]
#[serde(rename_all = "snake_case")]
pub enum TracingLevel {
/// "ERROR" level.
Error,
/// "WARN" level.
Warn,
/// "INFO" level.
Info,
/// "DEBUG" level.
Debug,
/// "TRACE" level.
Trace,
}
impl From<Level> for TracingLevel {
fn from(level: Level) -> Self {
match level {
Level::ERROR => Self::Error,
Level::WARN => Self::Warn,
Level::INFO => Self::Info,
Level::DEBUG => Self::Debug,
Level::TRACE => Self::Trace,
}
}
}
/// Kind of [`CallSiteData`] location: either a span, or an event.
#[derive(Debug, Clone, Copy, Hash, Serialize, Deserialize)]
#[serde(rename_all = "snake_case")]
pub enum CallSiteKind {
/// Call site is a span.
Span,
/// Call site is an event.
Event,
}
/// Data for a single tracing call site: either a span definition, or an event definition.
///
/// This corresponds to [`Metadata`] from the `tracing-core` library, but is (de)serializable.
#[derive(Debug, Clone, Hash, Serialize, Deserialize)]
pub struct CallSiteData {
/// Kind of the call site.
pub kind: CallSiteKind,
/// Name of the call site.
pub name: Cow<'static, str>,
/// Tracing target.
pub target: Cow<'static, str>,
/// Tracing level.
pub level: TracingLevel,
/// Path to the module where this call site is defined.
#[serde(default, skip_serializing_if = "Option::is_none")]
pub module_path: Option<Cow<'static, str>>,
/// Path to the file where this call site is defined.
#[serde(default, skip_serializing_if = "Option::is_none")]
pub file: Option<Cow<'static, str>>,
/// Line number for this call site.
#[serde(default, skip_serializing_if = "Option::is_none")]
pub line: Option<u32>,
/// Fields defined by this call site.
pub fields: Vec<Cow<'static, str>>,
}
impl From<&Metadata<'static>> for CallSiteData {
fn from(metadata: &Metadata<'static>) -> Self {
let kind = if metadata.is_span() {
CallSiteKind::Span
} else {
debug_assert!(metadata.is_event());
CallSiteKind::Event
};
let fields = metadata
.fields()
.iter()
.map(|field| Cow::Borrowed(field.name()));
Self {
kind,
name: Cow::Borrowed(metadata.name()),
target: Cow::Borrowed(metadata.target()),
level: TracingLevel::from(*metadata.level()),
module_path: metadata.module_path().map(Cow::Borrowed),
file: metadata.file().map(Cow::Borrowed),
line: metadata.line(),
fields: fields.collect(),
}
}
}
/// Event produced during tracing.
///
/// These events are emitted by a [`TracingEventSender`] and then consumed
/// by a [`TracingEventReceiver`] to pass tracing info across an API boundary.
///
/// [`TracingEventSender`]: crate::TracingEventSender
/// [`TracingEventReceiver`]: crate::TracingEventReceiver
#[derive(Debug, Clone, Serialize, Deserialize)]
#[serde(rename_all = "snake_case")]
#[non_exhaustive]
pub enum TracingEvent {
/// New call site.
NewCallSite {
/// Unique ID of the call site that will be used to refer to it in the following events.
id: MetadataId,
/// Information about the call site.
#[serde(flatten)]
data: CallSiteData,
},
/// New tracing span.
NewSpan {
/// Unique ID of the span that will be used to refer to it in the following events.
id: RawSpanId,
/// Parent span ID. `None` means using the contextual parent (i.e., the current span).
#[serde(default, skip_serializing_if = "Option::is_none")]
parent_id: Option<RawSpanId>,
/// ID of the span metadata.
metadata_id: MetadataId,
/// Values associated with the span.
values: TracedValues<String>,
},
/// New "follows from" relation between spans.
FollowsFrom {
/// ID of the follower span.
id: RawSpanId,
/// ID of the source span.
follows_from: RawSpanId,
},
/// Span was entered.
SpanEntered {
/// ID of the span.
id: RawSpanId,
},
/// Span was exited.
SpanExited {
/// ID of the span.
id: RawSpanId,
},
/// Span was cloned.
SpanCloned {
/// ID of the span.
id: RawSpanId,
},
/// Span was dropped (aka closed).
SpanDropped {
/// ID of the span.
id: RawSpanId,
},
/// New values recorded for a span.
ValuesRecorded {
/// ID of the span.
id: RawSpanId,
/// Recorded values.
values: TracedValues<String>,
},
/// New event.
NewEvent {
/// ID of the event metadata.
metadata_id: MetadataId,
/// Parent span ID. `None` means using the contextual parent (i.e., the current span).
#[serde(default, skip_serializing_if = "Option::is_none")]
parent: Option<RawSpanId>,
/// Values associated with the event.
values: TracedValues<String>,
},
}
impl TracingEvent {
/// Normalizes a captured sequence of events so that it does not contain information that
/// changes between program runs (e.g., metadata IDs) or due to minor refactoring
/// (source code lines). Normalized events can be used for snapshot testing
/// and other purposes when reproducibility is important.
pub fn normalize(events: &mut [Self]) {
let mut metadata_id_mapping = BTreeMap::new();
for event in events {
match event {
TracingEvent::NewCallSite { id, data } => {
// Replace metadata ID to be predictable.
let new_metadata_id = metadata_id_mapping.len() as MetadataId;
metadata_id_mapping.insert(*id, new_metadata_id);
*id = new_metadata_id;
// Normalize file paths to have `/` path delimiters.
#[cfg(feature = "std")]
if path::MAIN_SEPARATOR != '/' {
data.file = data
.file
.as_deref()
.map(|path| path.replace(path::MAIN_SEPARATOR, "/").into());
}
// Make event data not depend on specific lines, which could easily
// change due to refactoring etc.
data.line = None;
if matches!(data.kind, CallSiteKind::Event) {
data.name = Cow::Borrowed("event");
}
}
TracingEvent::NewSpan { metadata_id, .. }
| TracingEvent::NewEvent { metadata_id, .. } => {
let new_metadata_id = metadata_id_mapping.len() as MetadataId;
*metadata_id = *metadata_id_mapping
.entry(*metadata_id)
.or_insert(new_metadata_id);
}
_ => { /* No changes */ }
}
}
}
}