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//! A library to assist in reporting on the health of a system. #![warn( missing_docs, unused_import_braces, unused_imports, unused_qualifications )] #![deny(missing_debug_implementations, trivial_numeric_casts, unused_must_use)] #![forbid(unsafe_code)] use async_trait::async_trait; use parking_lot::Mutex; use std::{ borrow::Cow, error::Error as StdError, ops, sync::Arc, time::{Duration, Instant}, }; #[cfg(feature = "tokio_0_2")] use tokio_0_2::time::delay_for as sleep; #[cfg(all(feature = "tokio_0_3", not(feature = "tokio_0_2")))] use tokio_0_3::time::sleep; /// A health status reporter pub trait Reporter { /// The current health status without regard to any reliance criteria fn raw_status(&self) -> Status { self.last_check().into() } /// The current health status of the underlying health check or `None` if /// the current status should not be relyed upon fn status(&self) -> Option<Status> { Some(self.raw_status()) } /// The result of the most recent health check /// /// Because it may take multiple checks to cause the health status to /// change, this value may match the current health status. fn last_check(&self) -> Check; } /// A report of a single health check run /// /// Default: `Pass` /// /// ## Operations /// /// ``` /// use health::Check; /// /// assert_eq!(Check::Pass, !Check::Failed); /// assert_eq!(Check::Failed, !Check::Pass); /// /// assert_eq!(Check::Pass, Check::Pass & Check::Pass); /// assert_eq!(Check::Failed, Check::Pass & Check::Failed); /// assert_eq!(Check::Failed, Check::Failed & Check::Pass); /// assert_eq!(Check::Failed, Check::Failed & Check::Failed); /// /// assert_eq!(Check::Pass, Check::Pass | Check::Pass); /// assert_eq!(Check::Pass, Check::Pass | Check::Failed); /// assert_eq!(Check::Pass, Check::Failed | Check::Pass); /// assert_eq!(Check::Failed, Check::Failed | Check::Failed); /// /// assert_eq!(Check::Failed, Check::Pass ^ Check::Pass); /// assert_eq!(Check::Pass, Check::Pass ^ Check::Failed); /// assert_eq!(Check::Pass, Check::Failed ^ Check::Pass); /// assert_eq!(Check::Failed, Check::Failed ^ Check::Failed); /// ``` #[derive(Clone, Copy, Debug, Eq, PartialEq)] pub enum Check { /// The health check passed Pass, /// The health check failed Failed, } impl Default for Check { #[inline] fn default() -> Self { Self::Pass } } impl ops::Not for Check { type Output = Self; fn not(self) -> Self::Output { match self { Self::Pass => Self::Failed, Self::Failed => Self::Pass, } } } impl ops::BitAnd for Check { type Output = Self; fn bitand(self, rhs: Self) -> Self::Output { match (self, rhs) { (Self::Pass, Self::Pass) => Self::Pass, _ => Self::Failed, } } } impl ops::BitOr for Check { type Output = Self; fn bitor(self, rhs: Self) -> Self::Output { match (self, rhs) { (Self::Pass, _) | (_, Self::Pass) => Self::Pass, _ => Self::Failed, } } } impl ops::BitXor for Check { type Output = Self; fn bitxor(self, rhs: Self) -> Self::Output { if self != rhs { Self::Pass } else { Self::Failed } } } /// The status of a health check, accounting for allowable variance /// /// Default: `Healthy` /// /// ## Operations /// /// ``` /// use health::Status; /// /// assert_eq!(Status::Healthy, !Status::Unhealthy); /// assert_eq!(Status::Unhealthy, !Status::Healthy); /// /// assert_eq!(Status::Healthy, Status::Healthy & Status::Healthy); /// assert_eq!(Status::Unhealthy, Status::Healthy & Status::Unhealthy); /// assert_eq!(Status::Unhealthy, Status::Unhealthy & Status::Healthy); /// assert_eq!(Status::Unhealthy, Status::Unhealthy & Status::Unhealthy); /// /// assert_eq!(Status::Healthy, Status::Healthy | Status::Healthy); /// assert_eq!(Status::Healthy, Status::Healthy | Status::Unhealthy); /// assert_eq!(Status::Healthy, Status::Unhealthy | Status::Healthy); /// assert_eq!(Status::Unhealthy, Status::Unhealthy | Status::Unhealthy); /// /// assert_eq!(Status::Unhealthy, Status::Healthy ^ Status::Healthy); /// assert_eq!(Status::Healthy, Status::Healthy ^ Status::Unhealthy); /// assert_eq!(Status::Healthy, Status::Unhealthy ^ Status::Healthy); /// assert_eq!(Status::Unhealthy, Status::Unhealthy ^ Status::Unhealthy); /// ``` #[derive(Clone, Copy, Debug, Eq, PartialEq)] pub enum Status { /// The health check is reporting as healthy Healthy, /// The health check is reporting as unhealthy Unhealthy, } impl Default for Status { #[inline] fn default() -> Self { Self::Healthy } } impl From<Check> for Status { fn from(hc: Check) -> Self { match hc { Check::Pass => Self::Healthy, Check::Failed => Self::Unhealthy, } } } impl ops::Not for Status { type Output = Self; fn not(self) -> Self::Output { match self { Self::Healthy => Self::Unhealthy, Self::Unhealthy => Self::Healthy, } } } impl ops::BitAnd for Status { type Output = Self; fn bitand(self, rhs: Self) -> Self::Output { match (self, rhs) { (Self::Healthy, Self::Healthy) => Self::Healthy, _ => Self::Unhealthy, } } } impl ops::BitOr for Status { type Output = Self; fn bitor(self, rhs: Self) -> Self::Output { match (self, rhs) { (Self::Healthy, _) | (_, Self::Healthy) => Self::Healthy, _ => Self::Unhealthy, } } } impl ops::BitXor for Status { type Output = Self; fn bitxor(self, rhs: Self) -> Self::Output { if self != rhs { Self::Healthy } else { Self::Unhealthy } } } /// Configuration for a periodic health check /// /// Defaults: /// /// * Checks every 5 seconds /// * Becomes unhealthy after 3 consecutive failures /// * Becomes healthy on first success /// * Becomes unreliable if no completed checks in 15 seconds #[derive(Clone, Debug, PartialEq, Eq)] pub struct Config { /// Interval over which to periodically run the health check pub check_interval: Duration, /// Minimum number of consecutive failures to flip an healthy /// health check to unhealthy pub min_failures: u8, /// Minimum number of consecutive successes to flip an unhealthy /// health check to healthy pub min_successes: u8, /// Leeway between updated before the health check status is no longer /// considered current /// /// To deal with variation, this should generally not be less than /// twice the `check_interval`. pub leeway: Duration, } impl Default for Config { fn default() -> Self { Self { check_interval: Duration::from_secs(5), min_failures: 3, min_successes: 1, leeway: Duration::from_secs(15), } } } #[derive(Clone, Copy, Debug, Default)] struct State { status: Status, last_update: Duration, last_check: Check, count: u8, } /// A type that exposes a health check #[async_trait] pub trait Checkable { /// The error reported on a failed health check type Error: std::error::Error + Send + Sync + 'static; /// The action run to check the current health of the element /// /// `Ok(())` is interpreted as a passing result. Any `Err(_)` /// is interpreted as a failure. async fn check(&self) -> Result<(), Self::Error>; /// An identifier for the type of the checkable resource fn name(&self) -> Cow<str>; } /// A background healthcheck for checking the health of the MySQL Pool #[derive(Clone, Debug)] pub struct PeriodicChecker<C> { inner: Arc<PeriodicCheckerInner<C>>, } impl<C: Checkable> Reporter for PeriodicChecker<C> { /// The current health status without consideration for when /// the health status was last updated #[inline] fn raw_status(&self) -> Status { self.inner.raw_status() } /// The current health status or `None` if the health check hasn't /// updated its internal state within the leeway time #[inline] fn status(&self) -> Option<Status> { self.inner.status() } /// The result of the most recent health check #[inline] fn last_check(&self) -> Check { self.inner.last_check() } } impl<C: Checkable> PeriodicChecker<C> { /// Creates a new health check for the MySQL pool pub fn new(checkable: C, config: Config) -> Self { Self { inner: Arc::new(PeriodicCheckerInner { checkable, initialized: Instant::now(), state: Mutex::new(State::default()), config, }), } } /// Begins the health check loop and never returns pub async fn run(self) -> ! { self.inner.run().await } } #[derive(Debug)] struct PeriodicCheckerInner<C> { checkable: C, initialized: Instant, state: Mutex<State>, config: Config, } impl<C: Checkable> Reporter for PeriodicCheckerInner<C> { fn raw_status(&self) -> Status { self.state.lock().status } fn status(&self) -> Option<Status> { let state = self.state.lock(); let now = self.initialized.elapsed(); if now - state.last_update > self.config.leeway { None } else { Some(state.status) } } fn last_check(&self) -> Check { self.state.lock().last_check } } impl<C: Checkable> PeriodicCheckerInner<C> { async fn run(self: Arc<Self>) -> ! { let mut delay = sleep(Duration::from_secs(0)); loop { delay.await; delay = sleep(self.config.check_interval); let result = self.checkable.check().await; let mut state = self.state.lock(); state.last_update = self.initialized.elapsed(); let prior_status = state.status; let error = result.err(); let this_check = if error.is_none() { Check::Pass } else { Check::Failed }; if state.last_check != this_check { state.count = 0; } state.count = state.count.saturating_add(1); let new_status = if this_check == Check::Pass && state.status == Status::Unhealthy && state.count >= self.config.min_successes { Status::Healthy } else if this_check == Check::Failed && state.status == Status::Healthy && state.count >= self.config.min_failures { Status::Unhealthy } else { state.status }; let count = state.count; state.last_check = this_check; state.status = new_status; drop(state); let module = &*self.checkable.name(); match (new_status, &error) { // Report errors while unhealthy and still failing health checks (Status::Unhealthy, Some(error)) => { tracing::error!( error = error as &dyn StdError, check = ?this_check, status = ?new_status, count, module, "healthcheck" ); } // Report warnings while healthy but reporting failing health checks (Status::Healthy, Some(error)) => { tracing::warn!( error = error as &dyn StdError, check = ?this_check, status = ?new_status, count, module, "healthcheck" ); } // Report info while unhealthy but passing health checks (Status::Unhealthy, None) => { tracing::info!( check = ?this_check, status = ?new_status, count, module, "healthcheck" ); } // Report info if just becoming healthy (Status::Healthy, None) if prior_status == Status::Unhealthy => { tracing::info!( check = ?this_check, status = ?new_status, count, module, "healthcheck" ); } // Report debug if healthy and passing health checks (Status::Healthy, None) => { tracing::debug!( check = ?this_check, status = ?new_status, count, module, "healthcheck" ); } } } } }