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//! A bridge from [`tracing`] //! //! Traditionally, applications used separate instrumentation for metrics and logging. That is //! tiresome to set up. Using [`tracing`] offers an opportunity to use single instrumentation and //! export as both. //! //! This crate exports metrics through the [`dipstick`] metrics library, provided the //! instrumentation uses specific attributes to events and spans. To use it: //! //! * Register the [`DipstickLayer`] to consume the spans and events. //! * Use the `metrics.scope` on spans to create hierarchy of the metrics. //! * Mark the spans and events with further `metrics.*` attributes to collect metrics of specific //! types and names. //! //! # Recognized attributes //! //! Whenever there's a span or event with one of these attributes, a metric is collected whenever //! it is encountered. The value of the attribute is the name of the metric and the type (the thing //! after the `metrics.`) corresponds to the metric types in [`dipstick`]'s [`InputScope`]. Spans //! happen when they are created and some effects happen when they are closed/destroyed. //! //! * `metrics.counter="name"`: Adds 1 to the metric counter called `name`. //! * `metrics.level="name"`: Adds 1 to the level called `name`. If it is present on a span, the 1 //! is subtracted when it is closed (it's more useful on spans). //! * `metrics.gauge="name"`: Sets the gauge to 1. This one is more useful in the second form //! below. //! * `metrics.time="name"`: Records the time between the creation of the span and its destruction. //! This attribute is accepted only on spans. //! * `metrics.scope="scope-name"`: Names of metrics that are inside this span get prefixed by this //! name, eg. their names will be `scope-name.name`. Nested spans with this attributes accumulate //! the name, eg `outer-scope-name.inner-scope-name.name`. This is accepted on spans only. //! * `metrics.scope.full="scope-name"`: Similar to the above, but the name is not nested, it is //! replaced. //! //! The `counter`, `level` and `gauge` accept alternative variant of `metrics.type.name=value` (for //! example, `metrics.gauge.name=42`), which uses the given value instead of `1`. //! //! Unfortunately, typos don't cause compile errors, they are just ignored :-(. //! //! # Naming //! //! While the metrics are sent into the [`dipstick`] library, the attribute naming is quite //! general. This is on purpose. The author envisions that other crates might offer similar //! functionality, but export the metrics to a different library. In such case it is beneficial if //! the attributes are the same ‒ in such case changing the "backend" means only different //! initialization while the instrumentation of the whole code stays the same. //! //! # Crate status //! //! * There are some limitations about filtering (see the note at [`DipstickLayer`]). They may be //! fixed either in [`tracing_subscriber`] or by changes in here, but both needs some work. //! * There are several performance inefficiencies that need to be eliminated. //! * The crate has been tested only lightly and it's possible it might not act correctly in some //! corner cases. //! //! So, there's still some work to happen (and help in doing it is welcome). On the other hand, it //! is unlikely to cause some _serious_ problems, only incorrect metric readings. //! //! # Examples //! //! ``` //! use std::thread; //! use std::time::Duration; //! //! use dipstick::{AtomicBucket, ScheduleFlush, Stream}; //! use log::LevelFilter; //! use tracing::{debug, info_span, subscriber}; //! use tracing_dipstick::DipstickLayer; //! use tracing_subscriber::layer::SubscriberExt; //! use tracing_subscriber::Registry; //! //! fn main() { //! /* //! * We use the log-always integration of tracing here and route that to the env logger, that has //! * INFO enabled by default and can override by RUST_LOG to something else. //! * //! * We could use tracing_subscriber::fmt, *but* the EnvFilter there unfortunately disables //! * events/spans for the whole stack, not for logging only. And we want all the metrics while we //! * want only certain level of events. //! */ //! env_logger::builder() //! .filter_level(LevelFilter::Info) //! .parse_default_env() //! .init(); //! //! let root = AtomicBucket::new(); //! root.stats(dipstick::stats_all); //! root.drain(Stream::write_to_stdout()); //! let _flush = root.flush_every(Duration::from_secs(5)); //! //! let bridge = DipstickLayer::new(root); //! let subscriber = Registry::default().with(bridge); //! //! subscriber::set_global_default(subscriber).unwrap(); //! //! const CNT: usize = 10; //! let _yaks = info_span!("Shaving yaks", cnt = CNT, metrics.scope = "shaving").entered(); //! for i in 0..CNT { //! let _this_yak = info_span!( //! "Yak", //! metrics.gauge.order = i, //! metrics.scope = "yak", //! metrics.time = "time", //! metrics.level = "active" //! ) //! .entered(); //! debug!(metrics.counter = "started", "Starting shaving"); //! thread::sleep(Duration::from_millis(60)); //! debug!(metrics.counter = "done", metrics.counter.legs = 4, "Shaving done"); //! } //! } //! //! ``` //! //! [`tracing`]: https://docs.rs/tracing #![doc(test(attr(deny(warnings))))] #![forbid(unsafe_code)] #![warn(missing_docs)] use std::fmt::Debug; use dipstick::{InputScope, Level, Prefixed, TimeHandle, Timer}; use once_cell::unsync::Lazy; use tracing_core::field::{Field, Visit}; use tracing_core::span::{Attributes, Id}; use tracing_core::{Event, Subscriber}; use tracing_subscriber::layer::{Context, Layer}; use tracing_subscriber::registry::LookupSpan; const SCOPE_NAME: &str = "metrics.scope"; const SCOPE_NAME_FULL: &str = "metrics.scope.full"; #[derive(Copy, Clone, Debug)] enum MetricType { Counter, Gauge, Level, Timer, } impl MetricType { fn measure<P: MetricPoint>(self, point: &mut P, name: &str, value: i64) { let scope = point.scope(); match self { MetricType::Counter => scope.counter(name).count(value as _), MetricType::Gauge => scope.gauge(name).value(value), MetricType::Level => { let level = scope.level(name); level.adjust(value); point.push_level(level, value); } MetricType::Timer => { let timer = scope.timer(name); let start = timer.start(); point.push_timer(timer, start); } } } } const METRIC_TYPES: &[(&str, &str, MetricType, bool)] = &[ ( "metrics.counter", "metrics.counter.", MetricType::Counter, true, ), ("metrics.gauge", "metrics.gauge.", MetricType::Gauge, true), ("metrics.level", "metrics.level.", MetricType::Level, true), ("metrics.time", "", MetricType::Timer, false), ]; trait MetricPoint { const SCOPED: bool; type Scope: InputScope; fn push_timer(&mut self, timer: Timer, start: TimeHandle); fn push_level(&mut self, level: Level, decrement: i64); fn scope(&self) -> &Self::Scope; } struct PointWrap<P>(P); impl<P: MetricPoint> Visit for PointWrap<P> { fn record_debug(&mut self, _: &Field, _: &dyn Debug) {} fn record_str(&mut self, field: &Field, value: &str) { let name = field.name(); for tp in METRIC_TYPES { if (tp.3 || P::SCOPED) && name == tp.0 { tp.2.measure(&mut self.0, value, 1); break; } } } fn record_i64(&mut self, field: &Field, value: i64) { let name = field.name(); for tp in METRIC_TYPES { if tp.3 && name.starts_with(tp.1) { tp.2.measure(&mut self.0, &name[tp.1.len()..], value); } } } fn record_u64(&mut self, field: &Field, value: u64) { self.record_i64(field, value as _); } } #[derive(Clone)] struct Scope<S> { scope: S, // TODO: Small vecs? Put into the same vec to save one allocation? timers: Vec<(Timer, TimeHandle)>, levels: Vec<(Level, i64)>, // TODO: CPU timers } impl<S> Drop for Scope<S> { fn drop(&mut self) { for (timer, start) in self.timers.drain(..) { timer.stop(start); } for (level, decrement) in self.levels.drain(..) { level.adjust(-decrement); } } } impl<S: InputScope> MetricPoint for Scope<S> { const SCOPED: bool = true; type Scope = S; fn push_level(&mut self, level: Level, decrement: i64) { self.levels.push((level, decrement)); } fn push_timer(&mut self, timer: Timer, start: TimeHandle) { self.timers.push((timer, start)); } fn scope(&self) -> &S { &self.scope } } impl<S, F> MetricPoint for Lazy<S, F> where S: InputScope, F: FnOnce() -> S, { const SCOPED: bool = false; type Scope = S; fn push_timer(&mut self, _: Timer, _: TimeHandle) { unreachable!("Timers are not supported on events"); } fn push_level(&mut self, _: Level, _: i64) { // Levels on events are decremented manually, not at the end of some scope } fn scope(&self) -> &S { self } } /// The bridge from [`tracing`](https://docs.rs/tracing) to [`dipstick`]. /// /// This takes information from tracing and propagates them into [`dipstick`] as metrics. It works /// as [`Layer`]. /// /// # Warning /// /// Currently, [`tracing_subscriber`] doesn't allow filtering on per-layer basis. That means if /// there's another layer that filters (for example based on the level), it'll impact this layer /// too. This would negatively impact the gathered metrics as this expects to get them all. /// /// It has been observed to work together with the `tracing`s `log-always` feature. /// /// Future versions might bypass the [`Layer`] system and wrap a /// [`Subscriber`][tracing_core::Subscriber] directly. /// /// # Examples /// /// ```rust /// use std::time::Duration; /// /// use dipstick::{AtomicBucket, ScheduleFlush, Stream}; /// use log::LevelFilter; /// use tracing::subscriber; /// use tracing_dipstick::DipstickLayer; /// use tracing_subscriber::layer::SubscriberExt; /// use tracing_subscriber::Registry; /// /// env_logger::builder() /// .filter_level(LevelFilter::Info) /// .parse_default_env() /// .init(); /// /// let root = AtomicBucket::new(); /// root.stats(dipstick::stats_all); /// root.drain(Stream::write_to_stdout()); /// let _flush = root.flush_every(Duration::from_secs(5)); /// /// let bridge = DipstickLayer::new(root); /// let subscriber = Registry::default().with(bridge); /// /// subscriber::set_global_default(subscriber).unwrap(); /// ``` #[derive(Copy, Clone, Debug, Default)] pub struct DipstickLayer<S> { scope: S, } impl<S> DipstickLayer<S> where S: Clone + InputScope + Prefixed + 'static, { /// Creates the bridge. /// /// Expects the scope into which it will put metrics. pub fn new(input_scope: S) -> Self { DipstickLayer { scope: input_scope } } } impl<S, I> Layer<I> for DipstickLayer<S> where S: Clone + InputScope + Prefixed + Send + Sync + 'static, I: Subscriber, for<'l> I: LookupSpan<'l>, { fn new_span(&self, attrs: &Attributes, id: &Id, ctx: Context<I>) { let named = |scope: &S| -> S { let mut named: Option<S> = None; struct NameVisitor<'a, S> { target: &'a mut Option<S>, src: &'a S, } impl<S> Visit for NameVisitor<'_, S> where S: Prefixed, { fn record_debug(&mut self, _: &Field, _: &dyn Debug) {} fn record_str(&mut self, field: &Field, value: &str) { let name = field.name(); if name == SCOPE_NAME { *self.target = Some(self.src.add_name(value)); } else if name == SCOPE_NAME_FULL { *self.target = Some(self.src.named(value)); } } } attrs.record(&mut NameVisitor { target: &mut named, src: scope, }); named.unwrap_or_else(|| scope.clone()) }; let scope = ctx .lookup_current() .and_then(|current| { current .extensions() .get::<Scope<S>>() .map(|Scope { scope: s, .. }| named(s)) }) .unwrap_or_else(|| named(&self.scope)); let mut scope = PointWrap(Scope { scope, timers: Vec::new(), levels: Vec::new(), }); attrs.record(&mut scope); ctx.span(id) .expect("Missing newly created span") .extensions_mut() .insert(scope.0); } // TODO: How about cloning/creating new IDs for spans? fn on_event(&self, event: &Event, ctx: Context<I>) { // TODO: Currently, we store a scope in each span. Instead we should store it only in the // ones that are interesting. In particular: // * Score on creation only if the span itself touches metrics (either has some or has a // metric scope). // * Initialize it lazily on the first access. But extensions_mut might be slower? let scope = Lazy::new(|| { ctx.lookup_current() .map(|c| { // FIXME: It would be nice to avoid the clone. That should be possible, in // theory. c.extensions() .get::<Scope<S>>() .expect("Missing prepared scope") .scope .clone() }) .unwrap_or_else(|| self.scope.clone()) }); event.record(&mut PointWrap(scope)); } }