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//! //! Definition of histograms. //! //! Histograms represent measures on a set of entities known at //! compile-time. In some cases, the set of entities is not known //! at compile-time (e.g. plug-ins, dates), in which case you should //! rather use [Keyed histograms](../keyed.index.html). //! use rustc_serialize::json::Json; use std::marker::PhantomData; use std::mem::size_of; use std::sync::atomic::{AtomicBool, Ordering}; use indexing::*; use misc::{vec_with_size, Flatten, LinearBuckets, SerializationFormat}; use service::{PrivateAccess, Service}; use task::{BackEnd, Op, PlainRawStorage}; /// /// A plain histogram. /// /// Histograms do not implement `Sync`, so an instance of `Histogram` /// cannot be shared by several threads. However, any histogram can be /// cloned as needed for concurrent use. /// /// # Performance //// /// Cloning a histogram is relatively cheap, both in terms of memory /// and in terms of speed (most histograms weigh ~40bytes on a x86-64 /// architecture). /// /// When the telemetry service is inactive, recording data to a /// histogram is very fast (essentially a dereference and an atomic /// fetch). When the telemetry service is active, the duration of /// recording data is comparable to the duration of sending a simple /// message to a `Sender`. /// pub trait Histogram<T>: Clone { /// /// Record a value in this histogram. /// /// If the service is currently inactive, this is a noop. /// fn record(&self, value: T) { self.record_cb(|| Some(value)) } /// /// Record a value in this histogram, as provided by a callback. /// /// If the service is currently inactive, this is a noop. /// /// If the callback returns `None`, no value is recorded. /// fn record_cb<F>(&self, _: F) where F: FnOnce() -> Option<T>; } /// Back-end features specific to plain histograms. impl BackEnd<Plain> { /// Instruct the Telemetry Task to record a value in an /// already registered histogram. fn raw_record(&self, k: &Key<Plain>, value: u32) { self.sender.send(Op::RecordPlain(k.index, value)).unwrap(); } /// Instruct the Telemetry Task to record the result of a callback /// in an already registered histogram. fn raw_record_cb<F, T>(&self, cb: F) -> bool where F: FnOnce() -> Option<T>, T: Flatten, { if let Some(k) = self.get_key() { if let Some(v) = cb() { self.raw_record(&k, v.as_u32()); true } else { false } } else { false } } } /// /// A histogram that ignores any input. /// /// Useful for histograms that can be activated/deactivated either at /// compile-time (e.g. because they are attached to specific versions /// of the application) or during startup (e.g. depending on /// command-line options). /// #[derive(Default)] pub struct Ignoring<T> { witness: PhantomData<T>, } impl<T> Ignoring<T> { /// /// Create an histogram that ignores any input. /// /// `Ignoring` histograms are effectively implemented as empty /// structs, without a back-end, so they take no memory. /// pub fn new() -> Ignoring<T> { Ignoring { witness: PhantomData, } } } impl<T> Histogram<T> for Ignoring<T> { fn record_cb<F>(&self, _: F) where F: FnOnce() -> Option<T>, { // Nothing to do. } } impl<T> Clone for Ignoring<T> { fn clone(&self) -> Self { Ignoring { witness: PhantomData, } } } /// /// /// Flag histograms. /// /// This histogram has only two states. Until the first call to /// `record()`, it is _unset_. Once `record()` has been called once, /// it is _set_ and won't change anymore. This type is useful if you /// need to track whether a feature was ever used during a session. /// /// /// With `SerializationFormat::SimpleJson`, these histograms are /// serialized as a plain number 0 (unset)/1 (set). /// pub struct Flag { back_end: BackEnd<Plain>, /// A cache used to avoid spamming the Task once the flag has been set. cache: AtomicBool, } /// The storage, owned by the Telemetry Task. struct FlagStorage { /// `true` once we have called `record`, `false` until then. encountered: bool, } impl PlainRawStorage for FlagStorage { fn store(&mut self, _: u32) { self.encountered = true; } fn to_json(&self, format: &SerializationFormat) -> Json { match format { SerializationFormat::SimpleJson => Json::I64(if self.encountered { 1 } else { 0 }), } } } impl Histogram<()> for Flag { fn record_cb<F>(&self, cb: F) where F: FnOnce() -> Option<()>, { if self.cache.load(Ordering::Relaxed) { // Don't bother with dereferencing values or sending // messages, the histogram is already full. return; } if self.back_end.raw_record_cb(cb) { self.cache.store(true, Ordering::Relaxed); } } } impl Flag { /// /// Create a new Flag histogram with a given name. /// /// Argument `name` is used as key when processing and exporting /// the data. Each `name` must be unique to the `Service`. /// /// # Panics /// /// If `name` is already used by another histogram in `service`. /// pub fn new(service: &Service, name: String) -> Flag { let storage = Box::new(FlagStorage { encountered: false }); let key = PrivateAccess::register_plain(service, name, storage); Flag { back_end: BackEnd::new(service, key), cache: AtomicBool::new(false), } } } impl Clone for Flag { fn clone(&self) -> Self { Flag { back_end: self.back_end.clone(), // The cache is not shared, but that's ok, it's just an // optimization. cache: AtomicBool::new(self.cache.load(Ordering::Relaxed)), } } } /// /// Linear histograms. /// /// /// Linear histograms classify numeric integer values into same-sized /// buckets. This type is typically used for percentages, or to store /// a relatively precise approximation of the amount of resources /// (time, memory) used by a section or a data structure. /// /// /// With `SerializationFormat::SimpleJson`, these histograms are /// serialized as an array of numbers, one per bucket, in the numeric /// order of buckets. pub struct Linear<T> where T: Flatten, { witness: PhantomData<T>, back_end: BackEnd<Plain>, } impl<T> Histogram<T> for Linear<T> where T: Flatten, { fn record_cb<F>(&self, cb: F) where F: FnOnce() -> Option<T>, { self.back_end.raw_record_cb(cb); } } impl<T> Linear<T> where T: Flatten, { /// /// Create a new Linear histogram with a given name. /// /// - `name` is used as key when processing and exporting /// the data. Each `name` must be unique to the `Service`. /// /// - `min` is the minimal value expected to be entered in this /// histogram. Any value lower than `min` is rounded up to `min`. /// /// - `max` is the maximal value expected to be entered in this /// histogram. Any value higher than `max` is rounded up to `max`. /// /// - `buckets` is the number of buckets in this histogram. For /// highest possible precision, use `buckets = max - min + 1`. /// In most cases, however, such precision is not needed, so you /// should use a lower number of buckets. /// /// /// # Performance /// /// Increasing the number of buckets increases the memory usage on /// the client by a few bytes per bucket. More importantly, it also /// increases the size of the payload, hence the total amount of /// data that the application will eventually upload to a central /// server. If your application has many clients and you wish to /// keep your server happy and your bandwidth costs manageable, /// don't use too many buckets. /// /// /// # Panics /// /// If `name` is already used by another histogram in `service`. /// /// If `min >= max`. /// /// If `buckets < max - min + 1`. /// pub fn new(service: &Service, name: String, min: u32, max: u32, buckets: usize) -> Linear<T> { assert!(size_of::<u32>() <= size_of::<usize>()); assert!(min < max); assert!(max - min + 1 >= buckets as u32); let shape = LinearBuckets::new(min, max, buckets); let storage = Box::new(LinearStorage::new(shape)); let key = PrivateAccess::register_plain(service, name, storage); Linear { witness: PhantomData, back_end: BackEnd::new(service, key), } } } struct LinearStorage { values: Vec<u32>, // We cannot use an array here, as this would make the struct unsized. shape: LinearBuckets, } impl LinearStorage { fn new(shape: LinearBuckets) -> LinearStorage { let vec = vec_with_size(shape.buckets, 0); LinearStorage { values: vec, shape } } } impl PlainRawStorage for LinearStorage { fn store(&mut self, value: u32) { let index = self.shape.get_bucket(value); self.values[index] += 1; } fn to_json(&self, _: &SerializationFormat) -> Json { let json = Json::Array(self.values.iter().map(|&x| Json::I64(x as i64)).collect()); json } } impl<T> Clone for Linear<T> where T: Flatten, { fn clone(&self) -> Self { Linear { witness: PhantomData, back_end: self.back_end.clone(), } } } /// /// /// Count histograms. /// /// A Count histogram simply accumulates the numbers passed with /// `record()`. Count histograms are useful, for instance, to know how /// many times a feature has been used, or how many times an error has /// been triggered. /// /// /// With `SerializationFormat::SimpleJson`, these histograms are /// serialized as a plain number. /// #[derive(Clone)] pub struct Count { back_end: BackEnd<Plain>, } // The storage, owned by the Telemetry Task. struct CountStorage { value: u32, } impl PlainRawStorage for CountStorage { fn store(&mut self, value: u32) { self.value += value; } fn to_json(&self, format: &SerializationFormat) -> Json { match format { SerializationFormat::SimpleJson => Json::I64(self.value as i64), } } } impl Histogram<u32> for Count { fn record_cb<F>(&self, cb: F) where F: FnOnce() -> Option<u32>, { self.back_end.raw_record_cb(cb); } } impl Count { /// /// Create a new Count histogram with a given name. /// /// Argument `name` is used as key when processing and exporting /// the data. Each `name` must be unique to the `Service`. /// /// # Panics /// /// If `name` is already used by another histogram in `service`. /// pub fn new(service: &Service, name: String) -> Count { let storage = Box::new(CountStorage { value: 0 }); let key = PrivateAccess::register_plain(service, name, storage); Count { back_end: BackEnd::new(service, key), } } } /// /// /// Enumerated histograms. /// /// Enumerated histogram generalize Count histograms to families of /// keys known at compile-time. They are useful, for instance, to know /// how often users have picked a specific choice from several, or how /// many times each kind of error has been triggered, etc. /// /// /// With `SerializationFormat::SimpleJson`, these histograms are /// serialized as an array of numbers, in the order of enum values. /// pub struct Enum<K> where K: Flatten, { witness: PhantomData<K>, back_end: BackEnd<Plain>, } // The storage, owned by the Telemetry Task. struct EnumStorage { values: Vec<u32>, } impl PlainRawStorage for EnumStorage { fn store(&mut self, value: u32) { self.values.resize(value as usize + 1, 0); self.values[value as usize] += 1; } fn to_json(&self, format: &SerializationFormat) -> Json { match format { SerializationFormat::SimpleJson => { Json::Array(self.values.iter().map(|&x| Json::I64(x as i64)).collect()) } } } } impl<K> Histogram<K> for Enum<K> where K: Flatten, { fn record_cb<F>(&self, cb: F) where F: FnOnce() -> Option<K>, { self.back_end.raw_record_cb(cb); } } impl<K> Enum<K> where K: Flatten, { /// /// Create a new Enum histogram with a given name. /// /// Argument `name` is used as key when processing and exporting /// the data. Each `name` must be unique to the `Service`. /// /// # Panics /// /// If `name` is already used by another histogram in `service`. /// pub fn new(service: &Service, name: String) -> Enum<K> { let storage = Box::new(EnumStorage { values: Vec::new() }); let key = PrivateAccess::register_plain(service, name, storage); Enum { witness: PhantomData, back_end: BackEnd::new(service, key), } } } impl<K> Clone for Enum<K> where K: Flatten, { fn clone(&self) -> Self { Enum { witness: PhantomData, back_end: self.back_end.clone(), } } }