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
//! A facade for tracing. //! //! This crate provides a pluggable API for tracing, akin to what [log] does for logging. //! //! Some available implementations are: //! * [tracing_chromium] - to emit Chromium's trace event format //! //! ### Example //! ``` //! #[macro_use] //! extern crate tracing_facade; //! //! #[macro_use] //! extern crate serde_json; //! //! use std::borrow::Cow; //! use std::sync::{Arc, Mutex}; //! //! #[derive(Clone, Debug)] //! struct Event { //! name: String, //! kind: tracing_facade::EventKind, //! metadata: tracing_facade::Metadata, //! } //! //! impl<'a> From<tracing_facade::Event<'a>> for Event { //! fn from(event: tracing_facade::Event) -> Self { //! Event { //! name: event.name.into_owned(), //! kind: event.kind, //! metadata: event.metadata, //! } //! } //! } //! //! struct Tracer { //! events: Arc<Mutex<Vec<Event>>> //! } //! //! impl Tracer { //! fn new() -> (Tracer, Arc<Mutex<Vec<Event>>>) { //! let vec = Arc::new(Mutex::new(Vec::new())); //! let tracer = Tracer { //! events: Arc::clone(&vec) //! }; //! (tracer, vec) //! } //! } //! //! //! impl tracing_facade::Tracer for Tracer { //! fn supports_metadata(&self) -> bool { //! true //! } //! //! fn record_event(&self, event: tracing_facade::Event) { //! self.events.lock().unwrap().push(event.into()); //! } //! //! fn flush(&self) {} //! } //! //! fn main() { //! let (tracer, tracer_events) = Tracer::new(); //! tracing_facade::set_boxed_tracer(Box::new(tracer)); //! { //! trace_scoped!("foo"); //! trace_begin!("bar", "value": 42); //! trace_end!("bar"); //! } //! //! let events = tracer_events.lock().unwrap().clone(); //! assert_eq!(events.len(), 4); //! assert_eq!(events[0].name, "foo"); //! assert_eq!(events[0].kind, tracing_facade::EventKind::SyncBegin); //! assert_eq!(events[0].metadata.as_json(), None); //! //! assert_eq!(events[1].name, "bar"); //! assert_eq!(events[1].kind, tracing_facade::EventKind::SyncBegin); //! assert_eq!(events[1].metadata.as_json(), Some(&json!({"value": 42}))); //! //! assert_eq!(events[2].name, "bar"); //! assert_eq!(events[2].kind, tracing_facade::EventKind::SyncEnd); //! assert_eq!(events[2].metadata.as_json(), None); //! //! assert_eq!(events[3].name, "foo"); //! assert_eq!(events[3].kind, tracing_facade::EventKind::SyncEnd); //! assert_eq!(events[3].metadata.as_json(), None); //! } //! ``` use std::borrow::Cow; use std::sync::atomic::{AtomicUsize, Ordering}; mod macros; pub use macros::*; pub enum Error {} /// A trait encompassing the operations required for tracing. pub trait Tracer: Sync + Send { /// Determines whether the [Tracer] is enabled. /// /// The trace macros use this to avoid doing work when unneeded. fn is_enabled(&self) -> bool { true } /// Specifies whether the [Tracer] can handle additional metadata. /// /// The trace macros use this to avoid constructing a [Metadata] object which will get immediately /// thrown away. fn supports_metadata(&self) -> bool { false } /// Record an [Event] to the Tracer. fn record_event(&self, event: Event); /// Flush any previously recorded [Event]s to the Tracer. fn flush(&self); } /// An enum representing the types of [Event]s that can occur. #[derive(Clone, Copy, Debug, PartialEq)] pub enum EventKind { /// The beginning of a synchronous duration. /// /// This represents the beginning of a duration on a particular thread. Durations can be nested, /// but must not overlap. SyncBegin, /// The end of a synchronous duration. /// /// This represents the end of a duration on a particular thread. Durations can be nested, /// but must not overlap. SyncEnd, } /// An event to trace. pub struct Event<'a> { /// The name of the [Event]. pub name: Cow<'a, str>, /// The type of [Event] which occurred. pub kind: EventKind, /// [Metadata] attached to the event. pub metadata: Metadata, } /// A struct containing metadata for an event. #[derive(Clone, Debug)] pub struct Metadata { json: Option<serde_json::Value>, } impl Metadata { pub fn as_json(&self) -> Option<&serde_json::Value> { self.json.as_ref() } pub fn into_json(self) -> Option<serde_json::Value> { self.json } pub fn from_json(json: serde_json::Value) -> Metadata { Metadata { json: Some(json) } } } impl Default for Metadata { fn default() -> Self { Metadata { json: None } } } /// Determines whether a [Tracer] has been installed, and if it is currently enabled. /// /// If a [Tracer] has been installed, returns the result of [Tracer::is_enabled]. /// Otherwise, returns false. pub fn is_enabled() -> bool { loop { match STATE.load(Ordering::Acquire) { UNINITIALIZED => return false, INITIALIZING => std::thread::yield_now(), INITIALIZED => return get_tracer_assume_initialized().is_enabled(), other => panic!("unexpected tracing_facade::STATE value: {}", other), } } } /// Determines whether a [Tracer] has been installed, and if it supports metadata. /// /// If a [Tracer] has been installed, returns the result of [Tracer::supports_metadata]. /// Otherwise, returns false. pub fn supports_metadata() -> bool { if is_enabled() { get_tracer_assume_initialized().supports_metadata() } else { false } } /// Records an Event to the installed [Tracer]. /// /// If a [Tracer] has been installed, invokes [Tracer::record_event] on it. /// Otherwise, does nothing. pub fn record_event(event: Event) { if is_enabled() { get_tracer_assume_initialized().record_event(event) } } /// Flushes the installed [Tracer]. /// /// If a [Tracer] has been installed, invokes [Tracer::flush] on it. /// Otherwise, does nothing. pub fn flush() { if is_enabled() { get_tracer_assume_initialized().flush() } } static mut TRACER: Option<&'static Tracer> = None; static STATE: AtomicUsize = AtomicUsize::new(UNINITIALIZED); /// The tracer hasn't been initialized yet. const UNINITIALIZED: usize = 0; /// The tracer has been initialized. const INITIALIZED: usize = 1; /// The tracer is in the process of initializing. const INITIALIZING: usize = 2; fn get_tracer_assume_initialized() -> &'static Tracer { unsafe { TRACER.unwrap() } } /// Installs a [Tracer]. /// /// Installation can only occur once; subsequent installations will panic. pub fn set_tracer(tracer: &'static Tracer) { set_tracer_impl(tracer); } /// Installs a [Tracer] contained in a [Box]. /// /// The contained [Tracer] will never be destroyed. /// Installation can only occur once; subsequent installations will panic. pub fn set_boxed_tracer(tracer: Box<Tracer>) { let raw = Box::into_raw(tracer); set_tracer_impl(unsafe { &*raw }); } fn set_tracer_impl(tracer: &'static Tracer) { loop { match STATE.compare_exchange(UNINITIALIZED, INITIALIZING, Ordering::AcqRel, Ordering::Relaxed) { Ok(_) => { // We've recorded ourselves as the initializer. unsafe { TRACER = Some(tracer); } STATE .compare_exchange(INITIALIZING, INITIALIZED, Ordering::AcqRel, Ordering::Relaxed) .unwrap(); return; } Err(UNINITIALIZED) => { // This should be impossible. unreachable!(); } Err(INITIALIZED) | Err(INITIALIZING) => { panic!("attempted to set a tracer after the tracing system was already initialized"); } Err(_) => { // This should also be impossible. unreachable!(); } } } }