| <!DOCTYPE html><html lang="en"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><meta name="generator" content="rustdoc"><meta name="description" content="Source of the Rust file `/root/.cargo/registry/src/github.com-1ecc6299db9ec823/tower-0.4.13/src/balance/pool/mod.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>mod.rs - source</title><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../../SourceSerif4-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../../FiraSans-Regular.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../../FiraSans-Medium.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../../SourceCodePro-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../../SourceSerif4-Bold.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../../SourceCodePro-Semibold.ttf.woff2"><link rel="stylesheet" href="../../../../normalize.css"><link rel="stylesheet" href="../../../../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" href="../../../../ayu.css" disabled><link rel="stylesheet" href="../../../../dark.css" disabled><link rel="stylesheet" href="../../../../light.css" id="themeStyle"><script id="default-settings" ></script><script src="../../../../storage.js"></script><script defer src="../../../../source-script.js"></script><script defer src="../../../../source-files.js"></script><script defer src="../../../../main.js"></script><noscript><link rel="stylesheet" href="../../../../noscript.css"></noscript><link rel="alternate icon" type="image/png" href="../../../../favicon-16x16.png"><link rel="alternate icon" type="image/png" href="../../../../favicon-32x32.png"><link rel="icon" type="image/svg+xml" href="../../../../favicon.svg"></head><body class="rustdoc source"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="sidebar"><a class="sidebar-logo" href="../../../../tower/index.html"><div class="logo-container"><img class="rust-logo" src="../../../../rust-logo.svg" alt="logo"></div></a></nav><main><div class="width-limiter"><nav class="sub"><a class="sub-logo-container" href="../../../../tower/index.html"><img class="rust-logo" src="../../../../rust-logo.svg" alt="logo"></a><form class="search-form"><div class="search-container"><span></span><input class="search-input" name="search" autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><div id="help-button" title="help" tabindex="-1"><a href="../../../../help.html">?</a></div><div id="settings-menu" tabindex="-1"><a href="../../../../settings.html" title="settings"><img width="22" height="22" alt="Change settings" src="../../../../wheel.svg"></a></div></div></form></nav><section id="main-content" class="content"><div class="example-wrap"><pre class="src-line-numbers"><span id="1">1</span> |
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| </pre><pre class="rust"><code><span class="doccomment">//! This module defines a load-balanced pool of services that adds new services when load is high. |
| //! |
| //! The pool uses `poll_ready` as a signal indicating whether additional services should be spawned |
| //! to handle the current level of load. Specifically, every time `poll_ready` on the inner service |
| //! returns `Ready`, [`Pool`] consider that a 0, and every time it returns `Pending`, [`Pool`] |
| //! considers it a 1. [`Pool`] then maintains an [exponential moving |
| //! average](https://en.wikipedia.org/wiki/Moving_average#Exponential_moving_average) over those |
| //! samples, which gives an estimate of how often the underlying service has been ready when it was |
| //! needed "recently" (see [`Builder::urgency`]). If the service is loaded (see |
| //! [`Builder::loaded_above`]), a new service is created and added to the underlying [`Balance`]. |
| //! If the service is underutilized (see [`Builder::underutilized_below`]) and there are two or |
| //! more services, then the latest added service is removed. In either case, the load estimate is |
| //! reset to its initial value (see [`Builder::initial`] to prevent services from being rapidly |
| //! added or removed. |
| </span><span class="attribute">#![deny(missing_docs)] |
| |
| </span><span class="kw">use </span><span class="kw">super</span>::p2c::Balance; |
| <span class="kw">use </span><span class="kw">crate</span>::discover::Change; |
| <span class="kw">use </span><span class="kw">crate</span>::load::Load; |
| <span class="kw">use </span><span class="kw">crate</span>::make::MakeService; |
| <span class="kw">use </span>futures_core::{ready, Stream}; |
| <span class="kw">use </span>pin_project_lite::pin_project; |
| <span class="kw">use </span>slab::Slab; |
| <span class="kw">use </span>std::{ |
| fmt, |
| future::Future, |
| pin::Pin, |
| task::{Context, Poll}, |
| }; |
| <span class="kw">use </span>tower_service::Service; |
| |
| <span class="attribute">#[cfg(test)] |
| </span><span class="kw">mod </span>test; |
| |
| <span class="attribute">#[derive(Debug, Clone, Copy, Eq, PartialEq)] |
| </span><span class="kw">enum </span>Level { |
| <span class="doccomment">/// Load is low -- remove a service instance. |
| </span>Low, |
| <span class="doccomment">/// Load is normal -- keep the service set as it is. |
| </span>Normal, |
| <span class="doccomment">/// Load is high -- add another service instance. |
| </span>High, |
| } |
| |
| <span class="macro">pin_project! </span>{ |
| <span class="doccomment">/// A wrapper around `MakeService` that discovers a new service when load is high, and removes a |
| /// service when load is low. See [`Pool`]. |
| </span><span class="kw">pub struct </span>PoolDiscoverer<MS, Target, Request> |
| <span class="kw">where |
| </span>MS: MakeService<Target, Request>, |
| { |
| maker: MS, |
| <span class="attribute">#[pin] |
| </span>making: <span class="prelude-ty">Option</span><MS::Future>, |
| target: Target, |
| load: Level, |
| services: Slab<()>, |
| died_tx: tokio::sync::mpsc::UnboundedSender<usize>, |
| <span class="attribute">#[pin] |
| </span>died_rx: tokio::sync::mpsc::UnboundedReceiver<usize>, |
| limit: <span class="prelude-ty">Option</span><usize>, |
| } |
| } |
| |
| <span class="kw">impl</span><MS, Target, Request> fmt::Debug <span class="kw">for </span>PoolDiscoverer<MS, Target, Request> |
| <span class="kw">where |
| </span>MS: MakeService<Target, Request> + fmt::Debug, |
| Target: fmt::Debug, |
| { |
| <span class="kw">fn </span>fmt(<span class="kw-2">&</span><span class="self">self</span>, f: <span class="kw-2">&mut </span>fmt::Formatter<<span class="lifetime">'_</span>>) -> fmt::Result { |
| f.debug_struct(<span class="string">"PoolDiscoverer"</span>) |
| .field(<span class="string">"maker"</span>, <span class="kw-2">&</span><span class="self">self</span>.maker) |
| .field(<span class="string">"making"</span>, <span class="kw-2">&</span><span class="self">self</span>.making.is_some()) |
| .field(<span class="string">"target"</span>, <span class="kw-2">&</span><span class="self">self</span>.target) |
| .field(<span class="string">"load"</span>, <span class="kw-2">&</span><span class="self">self</span>.load) |
| .field(<span class="string">"services"</span>, <span class="kw-2">&</span><span class="self">self</span>.services) |
| .field(<span class="string">"limit"</span>, <span class="kw-2">&</span><span class="self">self</span>.limit) |
| .finish() |
| } |
| } |
| |
| <span class="kw">impl</span><MS, Target, Request> Stream <span class="kw">for </span>PoolDiscoverer<MS, Target, Request> |
| <span class="kw">where |
| </span>MS: MakeService<Target, Request>, |
| MS::MakeError: Into<<span class="kw">crate</span>::BoxError>, |
| MS::Error: Into<<span class="kw">crate</span>::BoxError>, |
| Target: Clone, |
| { |
| <span class="kw">type </span>Item = <span class="prelude-ty">Result</span><Change<usize, DropNotifyService<MS::Service>>, MS::MakeError>; |
| |
| <span class="kw">fn </span>poll_next(<span class="self">self</span>: Pin<<span class="kw-2">&mut </span><span class="self">Self</span>>, cx: <span class="kw-2">&mut </span>Context<<span class="lifetime">'_</span>>) -> Poll<<span class="prelude-ty">Option</span><<span class="self">Self</span>::Item>> { |
| <span class="kw">let </span><span class="kw-2">mut </span>this = <span class="self">self</span>.project(); |
| |
| <span class="kw">while let </span>Poll::Ready(<span class="prelude-val">Some</span>(sid)) = this.died_rx.as_mut().poll_recv(cx) { |
| this.services.remove(sid); |
| <span class="macro">tracing::trace!</span>( |
| pool.services = this.services.len(), |
| message = <span class="string">"removing dropped service" |
| </span>); |
| } |
| |
| <span class="kw">if </span>this.services.is_empty() && this.making.is_none() { |
| <span class="kw">let _ </span>= <span class="macro">ready!</span>(this.maker.poll_ready(cx))<span class="question-mark">?</span>; |
| <span class="macro">tracing::trace!</span>(<span class="string">"construct initial pool connection"</span>); |
| this.making |
| .set(<span class="prelude-val">Some</span>(this.maker.make_service(this.target.clone()))); |
| } |
| |
| <span class="kw">if let </span>Level::High = this.load { |
| <span class="kw">if </span>this.making.is_none() { |
| <span class="kw">if </span>this |
| .limit |
| .map(|limit| this.services.len() >= limit) |
| .unwrap_or(<span class="bool-val">false</span>) |
| { |
| <span class="kw">return </span>Poll::Pending; |
| } |
| |
| <span class="macro">tracing::trace!</span>( |
| pool.services = this.services.len(), |
| message = <span class="string">"decided to add service to loaded pool" |
| </span>); |
| <span class="macro">ready!</span>(this.maker.poll_ready(cx))<span class="question-mark">?</span>; |
| <span class="macro">tracing::trace!</span>(<span class="string">"making new service"</span>); |
| <span class="comment">// TODO: it'd be great if we could avoid the clone here and use, say, &Target |
| </span>this.making |
| .set(<span class="prelude-val">Some</span>(this.maker.make_service(this.target.clone()))); |
| } |
| } |
| |
| <span class="kw">if let </span><span class="prelude-val">Some</span>(fut) = this.making.as_mut().as_pin_mut() { |
| <span class="kw">let </span>svc = <span class="macro">ready!</span>(fut.poll(cx))<span class="question-mark">?</span>; |
| this.making.set(<span class="prelude-val">None</span>); |
| |
| <span class="kw">let </span>id = this.services.insert(()); |
| <span class="kw">let </span>svc = DropNotifyService { |
| svc, |
| id, |
| notify: this.died_tx.clone(), |
| }; |
| <span class="macro">tracing::trace!</span>( |
| pool.services = this.services.len(), |
| message = <span class="string">"finished creating new service" |
| </span>); |
| <span class="kw-2">*</span>this.load = Level::Normal; |
| <span class="kw">return </span>Poll::Ready(<span class="prelude-val">Some</span>(<span class="prelude-val">Ok</span>(Change::Insert(id, svc)))); |
| } |
| |
| <span class="kw">match </span>this.load { |
| Level::High => { |
| <span class="macro">unreachable!</span>(<span class="string">"found high load but no Service being made"</span>); |
| } |
| Level::Normal => Poll::Pending, |
| Level::Low <span class="kw">if </span>this.services.len() == <span class="number">1 </span>=> Poll::Pending, |
| Level::Low => { |
| <span class="kw-2">*</span>this.load = Level::Normal; |
| <span class="comment">// NOTE: this is a little sad -- we'd prefer to kill short-living services |
| </span><span class="kw">let </span>rm = this.services.iter().next().unwrap().<span class="number">0</span>; |
| <span class="comment">// note that we _don't_ remove from self.services here |
| // that'll happen automatically on drop |
| </span><span class="macro">tracing::trace!</span>( |
| pool.services = this.services.len(), |
| message = <span class="string">"removing service for over-provisioned pool" |
| </span>); |
| Poll::Ready(<span class="prelude-val">Some</span>(<span class="prelude-val">Ok</span>(Change::Remove(rm)))) |
| } |
| } |
| } |
| } |
| |
| <span class="doccomment">/// A [builder] that lets you configure how a [`Pool`] determines whether the underlying service is |
| /// loaded or not. See the [module-level documentation](self) and the builder's methods for |
| /// details. |
| /// |
| /// [builder]: https://rust-lang-nursery.github.io/api-guidelines/type-safety.html#builders-enable-construction-of-complex-values-c-builder |
| </span><span class="attribute">#[derive(Copy, Clone, Debug)] |
| </span><span class="kw">pub struct </span>Builder { |
| low: f64, |
| high: f64, |
| init: f64, |
| alpha: f64, |
| limit: <span class="prelude-ty">Option</span><usize>, |
| } |
| |
| <span class="kw">impl </span>Default <span class="kw">for </span>Builder { |
| <span class="kw">fn </span>default() -> <span class="self">Self </span>{ |
| Builder { |
| init: <span class="number">0.1</span>, |
| low: <span class="number">0.00001</span>, |
| high: <span class="number">0.2</span>, |
| alpha: <span class="number">0.03</span>, |
| limit: <span class="prelude-val">None</span>, |
| } |
| } |
| } |
| |
| <span class="kw">impl </span>Builder { |
| <span class="doccomment">/// Create a new builder with default values for all load settings. |
| /// |
| /// If you just want to use the defaults, you can just use [`Pool::new`]. |
| </span><span class="kw">pub fn </span>new() -> <span class="self">Self </span>{ |
| <span class="self">Self</span>::default() |
| } |
| |
| <span class="doccomment">/// When the estimated load (see the [module-level docs](self)) drops below this |
| /// threshold, and there are at least two services active, a service is removed. |
| /// |
| /// The default value is 0.01. That is, when one in every 100 `poll_ready` calls return |
| /// `Pending`, then the underlying service is considered underutilized. |
| </span><span class="kw">pub fn </span>underutilized_below(<span class="kw-2">&mut </span><span class="self">self</span>, low: f64) -> <span class="kw-2">&mut </span><span class="self">Self </span>{ |
| <span class="self">self</span>.low = low; |
| <span class="self">self |
| </span>} |
| |
| <span class="doccomment">/// When the estimated load (see the [module-level docs](self)) exceeds this |
| /// threshold, and no service is currently in the process of being added, a new service is |
| /// scheduled to be added to the underlying [`Balance`]. |
| /// |
| /// The default value is 0.5. That is, when every other call to `poll_ready` returns |
| /// `Pending`, then the underlying service is considered highly loaded. |
| </span><span class="kw">pub fn </span>loaded_above(<span class="kw-2">&mut </span><span class="self">self</span>, high: f64) -> <span class="kw-2">&mut </span><span class="self">Self </span>{ |
| <span class="self">self</span>.high = high; |
| <span class="self">self |
| </span>} |
| |
| <span class="doccomment">/// The initial estimated load average. |
| /// |
| /// This is also the value that the estimated load will be reset to whenever a service is added |
| /// or removed. |
| /// |
| /// The default value is 0.1. |
| </span><span class="kw">pub fn </span>initial(<span class="kw-2">&mut </span><span class="self">self</span>, init: f64) -> <span class="kw-2">&mut </span><span class="self">Self </span>{ |
| <span class="self">self</span>.init = init; |
| <span class="self">self |
| </span>} |
| |
| <span class="doccomment">/// How aggressively the estimated load average is updated. |
| /// |
| /// This is the α parameter of the formula for the [exponential moving |
| /// average](https://en.wikipedia.org/wiki/Moving_average#Exponential_moving_average), and |
| /// dictates how quickly new samples of the current load affect the estimated load. If the |
| /// value is closer to 1, newer samples affect the load average a lot (when α is 1, the load |
| /// average is immediately set to the current load). If the value is closer to 0, newer samples |
| /// affect the load average very little at a time. |
| /// |
| /// The given value is clamped to `[0,1]`. |
| /// |
| /// The default value is 0.05, meaning, in very approximate terms, that each new load sample |
| /// affects the estimated load by 5%. |
| </span><span class="kw">pub fn </span>urgency(<span class="kw-2">&mut </span><span class="self">self</span>, alpha: f64) -> <span class="kw-2">&mut </span><span class="self">Self </span>{ |
| <span class="self">self</span>.alpha = alpha.max(<span class="number">0.0</span>).min(<span class="number">1.0</span>); |
| <span class="self">self |
| </span>} |
| |
| <span class="doccomment">/// The maximum number of backing `Service` instances to maintain. |
| /// |
| /// When the limit is reached, the load estimate is clamped to the high load threshhold, and no |
| /// new service is spawned. |
| /// |
| /// No maximum limit is imposed by default. |
| </span><span class="kw">pub fn </span>max_services(<span class="kw-2">&mut </span><span class="self">self</span>, limit: <span class="prelude-ty">Option</span><usize>) -> <span class="kw-2">&mut </span><span class="self">Self </span>{ |
| <span class="self">self</span>.limit = limit; |
| <span class="self">self |
| </span>} |
| |
| <span class="doccomment">/// See [`Pool::new`]. |
| </span><span class="kw">pub fn </span>build<MS, Target, Request>( |
| <span class="kw-2">&</span><span class="self">self</span>, |
| make_service: MS, |
| target: Target, |
| ) -> Pool<MS, Target, Request> |
| <span class="kw">where |
| </span>MS: MakeService<Target, Request>, |
| MS::Service: Load, |
| <MS::Service <span class="kw">as </span>Load>::Metric: std::fmt::Debug, |
| MS::MakeError: Into<<span class="kw">crate</span>::BoxError>, |
| MS::Error: Into<<span class="kw">crate</span>::BoxError>, |
| Target: Clone, |
| { |
| <span class="kw">let </span>(died_tx, died_rx) = tokio::sync::mpsc::unbounded_channel(); |
| <span class="kw">let </span>d = PoolDiscoverer { |
| maker: make_service, |
| making: <span class="prelude-val">None</span>, |
| target, |
| load: Level::Normal, |
| services: Slab::new(), |
| died_tx, |
| died_rx, |
| limit: <span class="self">self</span>.limit, |
| }; |
| |
| Pool { |
| balance: Balance::new(Box::pin(d)), |
| options: <span class="kw-2">*</span><span class="self">self</span>, |
| ewma: <span class="self">self</span>.init, |
| } |
| } |
| } |
| |
| <span class="doccomment">/// A dynamically sized, load-balanced pool of `Service` instances. |
| </span><span class="kw">pub struct </span>Pool<MS, Target, Request> |
| <span class="kw">where |
| </span>MS: MakeService<Target, Request>, |
| MS::MakeError: Into<<span class="kw">crate</span>::BoxError>, |
| MS::Error: Into<<span class="kw">crate</span>::BoxError>, |
| Target: Clone, |
| { |
| <span class="comment">// the Pin<Box<_>> here is needed since Balance requires the Service to be Unpin |
| </span>balance: Balance<Pin<Box<PoolDiscoverer<MS, Target, Request>>>, Request>, |
| options: Builder, |
| ewma: f64, |
| } |
| |
| <span class="kw">impl</span><MS, Target, Request> fmt::Debug <span class="kw">for </span>Pool<MS, Target, Request> |
| <span class="kw">where |
| </span>MS: MakeService<Target, Request> + fmt::Debug, |
| MS::MakeError: Into<<span class="kw">crate</span>::BoxError>, |
| MS::Error: Into<<span class="kw">crate</span>::BoxError>, |
| Target: Clone + fmt::Debug, |
| MS::Service: fmt::Debug, |
| { |
| <span class="kw">fn </span>fmt(<span class="kw-2">&</span><span class="self">self</span>, f: <span class="kw-2">&mut </span>fmt::Formatter<<span class="lifetime">'_</span>>) -> fmt::Result { |
| f.debug_struct(<span class="string">"Pool"</span>) |
| .field(<span class="string">"balance"</span>, <span class="kw-2">&</span><span class="self">self</span>.balance) |
| .field(<span class="string">"options"</span>, <span class="kw-2">&</span><span class="self">self</span>.options) |
| .field(<span class="string">"ewma"</span>, <span class="kw-2">&</span><span class="self">self</span>.ewma) |
| .finish() |
| } |
| } |
| |
| <span class="kw">impl</span><MS, Target, Request> Pool<MS, Target, Request> |
| <span class="kw">where |
| </span>MS: MakeService<Target, Request>, |
| MS::Service: Load, |
| <MS::Service <span class="kw">as </span>Load>::Metric: std::fmt::Debug, |
| MS::MakeError: Into<<span class="kw">crate</span>::BoxError>, |
| MS::Error: Into<<span class="kw">crate</span>::BoxError>, |
| Target: Clone, |
| { |
| <span class="doccomment">/// Construct a new dynamically sized `Pool`. |
| /// |
| /// If many calls to `poll_ready` return `Pending`, `new_service` is used to |
| /// construct another `Service` that is then added to the load-balanced pool. |
| /// If many calls to `poll_ready` succeed, the most recently added `Service` |
| /// is dropped from the pool. |
| </span><span class="kw">pub fn </span>new(make_service: MS, target: Target) -> <span class="self">Self </span>{ |
| Builder::new().build(make_service, target) |
| } |
| } |
| |
| <span class="kw">type </span>PinBalance<S, Request> = Balance<Pin<Box<S>>, Request>; |
| |
| <span class="kw">impl</span><MS, Target, Req> Service<Req> <span class="kw">for </span>Pool<MS, Target, Req> |
| <span class="kw">where |
| </span>MS: MakeService<Target, Req>, |
| MS::Service: Load, |
| <MS::Service <span class="kw">as </span>Load>::Metric: std::fmt::Debug, |
| MS::MakeError: Into<<span class="kw">crate</span>::BoxError>, |
| MS::Error: Into<<span class="kw">crate</span>::BoxError>, |
| Target: Clone, |
| { |
| <span class="kw">type </span>Response = <PinBalance<PoolDiscoverer<MS, Target, Req>, Req> <span class="kw">as </span>Service<Req>>::Response; |
| <span class="kw">type </span>Error = <PinBalance<PoolDiscoverer<MS, Target, Req>, Req> <span class="kw">as </span>Service<Req>>::Error; |
| <span class="kw">type </span>Future = <PinBalance<PoolDiscoverer<MS, Target, Req>, Req> <span class="kw">as </span>Service<Req>>::Future; |
| |
| <span class="kw">fn </span>poll_ready(<span class="kw-2">&mut </span><span class="self">self</span>, cx: <span class="kw-2">&mut </span>Context<<span class="lifetime">'_</span>>) -> Poll<<span class="prelude-ty">Result</span><(), <span class="self">Self</span>::Error>> { |
| <span class="kw">if let </span>Poll::Ready(()) = <span class="self">self</span>.balance.poll_ready(cx)<span class="question-mark">? </span>{ |
| <span class="comment">// services was ready -- there are enough services |
| // update ewma with a 0 sample |
| </span><span class="self">self</span>.ewma <span class="kw-2">*</span>= <span class="number">1.0 </span>- <span class="self">self</span>.options.alpha; |
| |
| <span class="kw">let </span>discover = <span class="self">self</span>.balance.discover_mut().as_mut().project(); |
| <span class="kw">if </span><span class="self">self</span>.ewma < <span class="self">self</span>.options.low { |
| <span class="kw">if </span><span class="kw-2">*</span>discover.load != Level::Low { |
| <span class="macro">tracing::trace!</span>({ ewma = %<span class="self">self</span>.ewma }, <span class="string">"pool is over-provisioned"</span>); |
| } |
| <span class="kw-2">*</span>discover.load = Level::Low; |
| |
| <span class="kw">if </span>discover.services.len() > <span class="number">1 </span>{ |
| <span class="comment">// reset EWMA so we don't immediately try to remove another service |
| </span><span class="self">self</span>.ewma = <span class="self">self</span>.options.init; |
| } |
| } <span class="kw">else </span>{ |
| <span class="kw">if </span><span class="kw-2">*</span>discover.load != Level::Normal { |
| <span class="macro">tracing::trace!</span>({ ewma = %<span class="self">self</span>.ewma }, <span class="string">"pool is appropriately provisioned"</span>); |
| } |
| <span class="kw-2">*</span>discover.load = Level::Normal; |
| } |
| |
| <span class="kw">return </span>Poll::Ready(<span class="prelude-val">Ok</span>(())); |
| } |
| |
| <span class="kw">let </span>discover = <span class="self">self</span>.balance.discover_mut().as_mut().project(); |
| <span class="kw">if </span>discover.making.is_none() { |
| <span class="comment">// no services are ready -- we're overloaded |
| // update ewma with a 1 sample |
| </span><span class="self">self</span>.ewma = <span class="self">self</span>.options.alpha + (<span class="number">1.0 </span>- <span class="self">self</span>.options.alpha) * <span class="self">self</span>.ewma; |
| |
| <span class="kw">if </span><span class="self">self</span>.ewma > <span class="self">self</span>.options.high { |
| <span class="kw">if </span><span class="kw-2">*</span>discover.load != Level::High { |
| <span class="macro">tracing::trace!</span>({ ewma = %<span class="self">self</span>.ewma }, <span class="string">"pool is under-provisioned"</span>); |
| } |
| <span class="kw-2">*</span>discover.load = Level::High; |
| |
| <span class="comment">// don't reset the EWMA -- in theory, poll_ready should now start returning |
| // `Ready`, so we won't try to launch another service immediately. |
| // we clamp it to high though in case the # of services is limited. |
| </span><span class="self">self</span>.ewma = <span class="self">self</span>.options.high; |
| |
| <span class="comment">// we need to call balance again for PoolDiscover to realize |
| // it can make a new service |
| </span><span class="kw">return </span><span class="self">self</span>.balance.poll_ready(cx); |
| } <span class="kw">else </span>{ |
| <span class="kw-2">*</span>discover.load = Level::Normal; |
| } |
| } |
| |
| Poll::Pending |
| } |
| |
| <span class="kw">fn </span>call(<span class="kw-2">&mut </span><span class="self">self</span>, req: Req) -> <span class="self">Self</span>::Future { |
| <span class="self">self</span>.balance.call(req) |
| } |
| } |
| |
| <span class="attribute">#[doc(hidden)] |
| #[derive(Debug)] |
| </span><span class="kw">pub struct </span>DropNotifyService<Svc> { |
| svc: Svc, |
| id: usize, |
| notify: tokio::sync::mpsc::UnboundedSender<usize>, |
| } |
| |
| <span class="kw">impl</span><Svc> Drop <span class="kw">for </span>DropNotifyService<Svc> { |
| <span class="kw">fn </span>drop(<span class="kw-2">&mut </span><span class="self">self</span>) { |
| <span class="kw">let _ </span>= <span class="self">self</span>.notify.send(<span class="self">self</span>.id).is_ok(); |
| } |
| } |
| |
| <span class="kw">impl</span><Svc: Load> Load <span class="kw">for </span>DropNotifyService<Svc> { |
| <span class="kw">type </span>Metric = Svc::Metric; |
| <span class="kw">fn </span>load(<span class="kw-2">&</span><span class="self">self</span>) -> <span class="self">Self</span>::Metric { |
| <span class="self">self</span>.svc.load() |
| } |
| } |
| |
| <span class="kw">impl</span><Request, Svc: Service<Request>> Service<Request> <span class="kw">for </span>DropNotifyService<Svc> { |
| <span class="kw">type </span>Response = Svc::Response; |
| <span class="kw">type </span>Future = Svc::Future; |
| <span class="kw">type </span>Error = Svc::Error; |
| |
| <span class="kw">fn </span>poll_ready(<span class="kw-2">&mut </span><span class="self">self</span>, cx: <span class="kw-2">&mut </span>Context<<span class="lifetime">'_</span>>) -> Poll<<span class="prelude-ty">Result</span><(), <span class="self">Self</span>::Error>> { |
| <span class="self">self</span>.svc.poll_ready(cx) |
| } |
| |
| <span class="kw">fn </span>call(<span class="kw-2">&mut </span><span class="self">self</span>, req: Request) -> <span class="self">Self</span>::Future { |
| <span class="self">self</span>.svc.call(req) |
| } |
| } |
| </code></pre></div> |
| </section></div></main><div id="rustdoc-vars" data-root-path="../../../../" data-current-crate="tower" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |