tracing_tunnel/receiver/mod.rs
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570
//! `TracingEvent` receiver.
use serde::{Deserialize, Serialize};
use tracing_core::{
dispatcher::{self, Dispatch},
field::{self, FieldSet, Value, ValueSet},
span::{Attributes, Id, Record},
Event, Field, Metadata,
};
use std::{
collections::{HashMap, HashSet},
error, fmt, mem,
};
mod arena;
#[cfg(test)]
mod tests;
use self::arena::ARENA;
use crate::{CallSiteData, MetadataId, RawSpanId, TracedValue, TracedValues, TracingEvent};
enum CowValue<'a> {
Borrowed(&'a dyn Value),
Owned(Box<dyn Value + 'a>),
}
impl fmt::Debug for CowValue<'_> {
fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
match self {
Self::Borrowed(_) => formatter.debug_struct("Borrowed").finish_non_exhaustive(),
Self::Owned(_) => formatter.debug_struct("Owned").finish_non_exhaustive(),
}
}
}
impl<'a> CowValue<'a> {
fn as_ref(&self) -> &(dyn Value + 'a) {
match self {
Self::Borrowed(value) => value,
Self::Owned(boxed) => boxed.as_ref(),
}
}
}
impl TracedValue {
fn as_value(&self) -> CowValue<'_> {
CowValue::Borrowed(match self {
Self::Bool(value) => value,
Self::Int(value) => value,
Self::UInt(value) => value,
Self::Float(value) => value,
Self::String(value) => value,
Self::Object(value) => return CowValue::Owned(Box::new(field::debug(value))),
Self::Error(err) => {
let err = err as &(dyn error::Error + 'static);
return CowValue::Owned(Box::new(err));
}
})
}
}
#[derive(Debug, Clone, Serialize, Deserialize)]
struct SpanData {
metadata_id: MetadataId,
#[serde(default, skip_serializing_if = "Option::is_none")]
parent_id: Option<RawSpanId>,
ref_count: usize,
values: TracedValues<String>,
}
/// Information about span / event [`Metadata`] that is [serializable] and thus
/// can be persisted across multiple [`TracingEventReceiver`] lifetimes.
///
/// `PersistedMetadata` logically corresponds to a program executable (e.g., a WASM module),
/// not to its particular execution (e.g., a WASM module instance).
/// Multiple executions of the same executable can (and optimally should)
/// share `PersistedMetadata`.
///
/// [serializable]: https://docs.rs/serde/1/serde
#[derive(Debug, Clone, Default, Serialize, Deserialize)]
#[serde(transparent)]
pub struct PersistedMetadata {
inner: HashMap<MetadataId, CallSiteData>,
}
impl PersistedMetadata {
/// Returns the number of metadata entries.
pub fn len(&self) -> usize {
self.inner.len()
}
/// Checks whether this metadata collection is empty (i.e., no metadata was recorded yet).
pub fn is_empty(&self) -> bool {
self.inner.is_empty()
}
/// Iterates over contained call site metadata together with the corresponding
/// [`MetadataId`]s.
pub fn iter(&self) -> impl Iterator<Item = (MetadataId, &CallSiteData)> + '_ {
self.inner.iter().map(|(id, data)| (*id, data))
}
/// Merges entries from another `PersistedMetadata` instance.
pub fn extend(&mut self, other: Self) {
self.inner.extend(other.inner);
}
}
/// Information about alive tracing spans for a particular execution that is (de)serializable and
/// can be persisted across multiple [`TracingEventReceiver`] lifetimes.
///
/// Unlike [`PersistedMetadata`], `PersistedSpans` are specific to an executable invocation
/// (e.g., a WASM module instance). Compared to [`LocalSpans`], `PersistedSpans` have
/// the lifetime of the execution and not the host [`Subscriber`].
///
/// [`Subscriber`]: tracing_core::Subscriber
#[derive(Debug, Clone, Default, Serialize, Deserialize)]
#[serde(transparent)]
pub struct PersistedSpans {
inner: HashMap<RawSpanId, SpanData>,
}
impl PersistedSpans {
/// Returns the number of alive spans.
pub fn len(&self) -> usize {
self.inner.len()
}
/// Checks whether this span collection is empty (i.e., no spans were recorded yet).
pub fn is_empty(&self) -> bool {
self.inner.is_empty()
}
}
/// [`Subscriber`]-specific information about tracing spans for a particular execution
/// (e.g., a WASM module instance).
///
/// Unlike [`PersistedSpans`], this information is not serializable and lives along with
/// the host [`Subscriber`]. It is intended to be placed in something like
/// (an initially empty) `HashMap<K, LocalSpans>`, where `K` denotes the execution ID.
///
/// [`Subscriber`]: tracing_core::Subscriber
#[derive(Debug, Default)]
pub struct LocalSpans {
inner: HashMap<RawSpanId, Id>,
}
/// Error processing a [`TracingEvent`] by a [`TracingEventReceiver`].
#[derive(Debug)]
#[non_exhaustive]
pub enum ReceiveError {
/// The event contains a reference to an unknown [`Metadata`] ID.
UnknownMetadataId(MetadataId),
/// The event contains a reference to an unknown span ID.
UnknownSpanId(RawSpanId),
/// The event contains too many values.
TooManyValues {
/// Maximum supported number of values per event.
max: usize,
/// Actual number of values.
actual: usize,
},
}
impl fmt::Display for ReceiveError {
fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
match self {
Self::UnknownMetadataId(id) => write!(formatter, "unknown metadata ID: {id}"),
Self::UnknownSpanId(id) => write!(formatter, "unknown span ID: {id}"),
Self::TooManyValues { max, actual } => write!(
formatter,
"too many values provided ({actual}), should be no more than {max}"
),
}
}
}
impl error::Error for ReceiveError {}
macro_rules! create_value_set {
($fields:ident, $values:ident, [$($i:expr,)+]) => {
match $values.len() {
0 => $fields.value_set(&[]),
$(
$i => $fields.value_set(<&[_; $i]>::try_from($values).unwrap()),
)+
_ => unreachable!(),
}
};
}
/// Container for non-persisted information specific to a particular traced execution.
#[derive(Debug, Default)]
struct CurrentExecution {
uncommitted_span_ids: HashSet<RawSpanId>,
entered_span_ids: HashSet<RawSpanId>,
}
impl CurrentExecution {
fn remove_span(&mut self, id: RawSpanId) {
self.entered_span_ids.remove(&id);
self.uncommitted_span_ids.remove(&id);
}
fn finalize(&mut self, local_spans: &LocalSpans) {
for id in mem::take(&mut self.entered_span_ids) {
if let Some(local_id) = local_spans.inner.get(&id) {
TracingEventReceiver::dispatch(|dispatch| dispatch.exit(local_id));
}
}
for id in mem::take(&mut self.uncommitted_span_ids) {
if let Some(local_id) = local_spans.inner.get(&id) {
TracingEventReceiver::dispatch(|dispatch| dispatch.try_close(local_id.clone()));
}
}
}
}
/// Receiver of [`TracingEvent`]s produced by [`TracingEventSender`] that relays them
/// to the tracing infrastructure.
///
/// The receiver takes care of persisting [`Metadata`] / spans that can outlive
/// the lifetime of the host program (not just the `TracingEventReceiver` instance!).
/// As an example, in [the Tardigrade runtime], a consumer instance is created each time
/// a workflow is executed. It relays tracing events from the workflow logic (executed in WASM)
/// to the host.
///
/// In some cases, the execution tracked by `TracingEventReceiver` may finish abnormally.
/// (E.g., a WASM module instance panics while it has the `panic = abort` set
/// in the compilation options.) In these cases, all entered
/// spans are force-exited when the receiver is dropped. Additionally, spans created
/// by the execution are closed on drop as long as they are not [persisted](Self::persist()).
/// That is, persistence acts as a commitment of the execution results, while the default
/// behavior is rollback.
///
/// # ⚠ Resource consumption
///
/// To fit the API of the [`tracing-core`] crate, the receiver leaks string parts
/// of [`CallSiteData`]: we need a `&'static str` when we only have a `String`. Steps are taken
/// to limit the amount of leaked memory; we use a `static` string arena which checks whether
/// a particular string was already leaked, and reuses the existing `&'static str` if possible.
/// Still, this has negative implications regarding both memory consumption and performance,
/// so you probably should limit the number of executables to use with a `TracingEventReceiver`.
/// The number of *executions* of each executable is not a limiting factor.
///
/// # Examples
///
/// See [crate-level docs](index.html) for an example of usage.
///
/// [`TracingEventSender`]: crate::TracingEventSender
/// [the Tardigrade runtime]: https://github.com/slowli/tardigrade
/// [`tracing-core`]: https://docs.rs/tracing-core/
#[derive(Debug, Default)]
pub struct TracingEventReceiver {
metadata: HashMap<MetadataId, &'static Metadata<'static>>,
spans: PersistedSpans,
local_spans: LocalSpans,
current_execution: CurrentExecution,
}
impl TracingEventReceiver {
/// Maximum supported number of values in a span or event.
const MAX_VALUES: usize = 32;
/// Restores the receiver from the persisted metadata and tracing spans.
///
/// A receiver will work fine if `local_spans` information is lost (e.g., reset to the default
/// empty value). However, this is likely to result in span leakage
/// in the underlying [`Subscriber`]. On the other hand, mismatch between `metadata` / `spans`
/// and the execution producing [`TracingEvent`]s is **bad**; it will most likely result
/// in errors returned from [`Self::try_receive()`].
///
/// [`Subscriber`]: tracing_core::Subscriber
pub fn new(
metadata: PersistedMetadata,
spans: PersistedSpans,
local_spans: LocalSpans,
) -> Self {
let mut this = Self {
metadata: HashMap::new(),
spans,
local_spans,
current_execution: CurrentExecution::default(),
};
for (id, data) in metadata.inner {
this.on_new_call_site(id, data);
}
this
}
fn dispatch<T>(dispatch_fn: impl FnOnce(&Dispatch) -> T) -> T {
dispatch_fn(&dispatcher::get_default(Dispatch::clone))
}
fn metadata(&self, id: MetadataId) -> Result<&'static Metadata<'static>, ReceiveError> {
self.metadata
.get(&id)
.copied()
.ok_or(ReceiveError::UnknownMetadataId(id))
}
fn span(&self, id: RawSpanId) -> Result<&SpanData, ReceiveError> {
self.spans
.inner
.get(&id)
.ok_or(ReceiveError::UnknownSpanId(id))
}
fn span_mut(&mut self, id: RawSpanId) -> Result<&mut SpanData, ReceiveError> {
self.spans
.inner
.get_mut(&id)
.ok_or(ReceiveError::UnknownSpanId(id))
}
/// Returns `Ok(None)` if the local span ID is (validly) not set yet, and `Err(_)`
/// if it must have been set by this point.
fn map_span_id(&self, remote_id: RawSpanId) -> Result<Option<&Id>, ReceiveError> {
match self.local_spans.inner.get(&remote_id) {
Some(local_id) => Ok(Some(local_id)),
None => {
// Check if the the referenced span is alive.
if self.spans.inner.contains_key(&remote_id) {
Ok(None)
} else {
Err(ReceiveError::UnknownSpanId(remote_id))
}
}
}
}
fn ensure_values_len(values: &TracedValues<String>) -> Result<(), ReceiveError> {
if values.len() > Self::MAX_VALUES {
return Err(ReceiveError::TooManyValues {
actual: values.len(),
max: Self::MAX_VALUES,
});
}
Ok(())
}
fn generate_fields<'a>(
metadata: &'static Metadata<'static>,
values: &'a TracedValues<String>,
) -> Vec<(Field, CowValue<'a>)> {
let fields = metadata.fields();
values
.iter()
.filter_map(|(field_name, value)| {
fields
.field(field_name)
.map(|field| (field, value.as_value()))
})
.collect()
}
fn expand_fields<'a>(
values: &'a [(Field, CowValue<'_>)],
) -> Vec<(&'a Field, Option<&'a dyn Value>)> {
values
.iter()
.map(|(field, value)| (field, Some(value.as_ref())))
.collect()
}
fn create_values<'a>(
fields: &'a FieldSet,
values: &'a [(&Field, Option<&dyn Value>)],
) -> ValueSet<'a> {
create_value_set!(
fields,
values,
[
1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23,
24, 25, 26, 27, 28, 29, 30, 31, 32,
]
)
}
fn on_new_call_site(&mut self, id: MetadataId, data: CallSiteData) {
let (metadata, is_new) = ARENA.alloc_metadata(data);
self.metadata.insert(id, metadata);
if is_new {
Self::dispatch(|dispatch| dispatch.register_callsite(metadata));
}
}
fn create_local_span(&self, data: &SpanData) -> Result<Id, ReceiveError> {
let metadata = self.metadata(data.metadata_id)?;
let local_parent_id = data
.parent_id
.map(|parent_id| self.map_span_id(parent_id))
.transpose()?
.flatten();
let value_set = Self::generate_fields(metadata, &data.values);
let value_set = Self::expand_fields(&value_set);
let value_set = Self::create_values(metadata.fields(), &value_set);
let attributes = if let Some(local_parent_id) = local_parent_id {
Attributes::child_of(local_parent_id.clone(), metadata, &value_set)
} else {
Attributes::new(metadata, &value_set)
};
Ok(Self::dispatch(|dispatch| dispatch.new_span(&attributes)))
}
/// Tries to consume an event and relays it to the tracing infrastructure.
///
/// # Errors
///
/// Fails if the event contains a bogus reference to a call site or a span, or if it contains
/// too many values. In general, an error can mean that the consumer was restored
/// from an incorrect persisted state, or that the event generator is bogus (e.g.,
/// not a [`TracingEventSender`]).
///
/// [`TracingEventSender`]: crate::TracingEventSender
#[allow(clippy::missing_panics_doc, clippy::map_entry)] // false positive
pub fn try_receive(&mut self, event: TracingEvent) -> Result<(), ReceiveError> {
match event {
TracingEvent::NewCallSite { id, data } => {
self.on_new_call_site(id, data);
}
TracingEvent::NewSpan {
id,
parent_id,
metadata_id,
values,
} => {
Self::ensure_values_len(&values)?;
let data = SpanData {
metadata_id,
parent_id,
ref_count: 1,
values,
};
if !self.local_spans.inner.contains_key(&id) {
let local_id = self.create_local_span(&data)?;
self.local_spans.inner.insert(id, local_id);
}
self.spans.inner.insert(id, data);
self.current_execution.uncommitted_span_ids.insert(id);
}
TracingEvent::FollowsFrom { id, follows_from } => {
let local_id = self.map_span_id(id)?;
let local_follows_from = self.map_span_id(follows_from)?;
// TODO: properly handle remaining cases
if let (Some(id), Some(follows_from)) = (local_id, local_follows_from) {
Self::dispatch(|dispatch| {
dispatch.record_follows_from(id, follows_from);
});
}
}
TracingEvent::SpanEntered { id } => {
let local_id = if let Some(id) = self.map_span_id(id)? {
id.clone()
} else {
let data = self.span(id)?;
let local_id = self.create_local_span(data)?;
self.local_spans.inner.insert(id, local_id.clone());
local_id
};
self.current_execution.entered_span_ids.insert(id);
Self::dispatch(|dispatch| dispatch.enter(&local_id));
}
TracingEvent::SpanExited { id } => {
if let Some(local_id) = self.map_span_id(id)? {
Self::dispatch(|dispatch| dispatch.exit(local_id));
}
self.current_execution.entered_span_ids.remove(&id);
}
TracingEvent::SpanCloned { id } => {
let span = self.span_mut(id)?;
span.ref_count += 1;
// Dispatcher is intentionally not called: we handle ref counting locally.
}
TracingEvent::SpanDropped { id } => {
let span = self.span_mut(id)?;
span.ref_count -= 1;
if span.ref_count == 0 {
self.spans.inner.remove(&id);
self.current_execution.remove_span(id);
if let Some(local_id) = self.local_spans.inner.remove(&id) {
Self::dispatch(|dispatch| dispatch.try_close(local_id.clone()));
}
}
}
TracingEvent::ValuesRecorded { id, values } => {
Self::ensure_values_len(&values)?;
if let Some(local_id) = self.map_span_id(id)? {
let metadata = self.metadata(self.spans.inner[&id].metadata_id)?;
let values = Self::generate_fields(metadata, &values);
let values = Self::expand_fields(&values);
let values = Self::create_values(metadata.fields(), &values);
let values = Record::new(&values);
Self::dispatch(|dispatch| dispatch.record(local_id, &values));
}
let span = self.span_mut(id)?;
span.values.extend(values);
}
TracingEvent::NewEvent {
metadata_id,
parent,
values,
} => {
Self::ensure_values_len(&values)?;
let metadata = self.metadata(metadata_id)?;
let values = Self::generate_fields(metadata, &values);
let values = Self::expand_fields(&values);
let values = Self::create_values(metadata.fields(), &values);
let parent = parent.map(|id| self.map_span_id(id)).transpose()?.flatten();
let event = if let Some(parent) = parent {
Event::new_child_of(parent.clone(), metadata, &values)
} else {
Event::new(metadata, &values)
};
Self::dispatch(|dispatch| dispatch.event(&event));
}
}
Ok(())
}
/// Consumes an event and relays it to the tracing infrastructure.
///
/// # Panics
///
/// Panics in the same cases when [`Self::try_receive()`] returns an error.
pub fn receive(&mut self, event: TracingEvent) {
self.try_receive(event)
.expect("received bogus tracing event");
}
/// Persists [`Metadata`] produced by the previously consumed events. The returned
/// metadata should be merged into the metadata provided to [`Self::new()`].
pub fn persist_metadata(&self) -> PersistedMetadata {
let inner = self
.metadata
.iter()
.map(|(&id, &metadata)| (id, CallSiteData::from(metadata)))
.collect();
PersistedMetadata { inner }
}
/// Returns persisted and local spans.
pub fn persist(mut self) -> (PersistedSpans, LocalSpans) {
self.current_execution.uncommitted_span_ids.clear();
let spans = mem::take(&mut self.spans);
let local_spans = mem::take(&mut self.local_spans);
self.current_execution.finalize(&local_spans);
(spans, local_spans)
}
}
impl Drop for TracingEventReceiver {
fn drop(&mut self) {
self.current_execution.finalize(&self.local_spans);
}
}